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Biotechnology Group, School of Biosciences and Bioengineering, Indian Institute of Technology – Bombay, Powai, Mumbai 400 076, India
Correspondence
Prashant S. Phale
pphale{at}iitb.ac.in
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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-ketoglutarate at 1 mM concentration caused strains PP4 and PPD to grow faster than in the presence of isophthalate alone; however, no such effect was observed in strain ISP4. When grown on isophthalate, all strains showed activity of NADP-dependent GDH (NADP-GDH), while cells grown on glucose, 2x yeast extract-tryptone broth (2YT) or glutamate showed activities of both NAD-dependent GDH (NAD-GDH) and NADP-GDH. Activity staining, inhibition and thermal stability studies indicated the carbon source-dependent presence of two (GDHI and GDHII), three (GDHA, GDHB and GDHC) and one (GDHP) forms of NADP-GDH in strains PP4, PPD and ISP4, respectively. The results demonstrate the carbon source-dependent modulation of different forms of NADP-GDH in these bacterial strains. This modulation may help the efficient utilization of isophthalate as a carbon source by overcoming the inhibitory effect on GDH.
-KG, -ketoglutarate; NAD-GDH, NAD-dependent GDH; NADP-GDH, NADP-dependent GDH |
INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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; Keyser et al., 1976; Tepper, 1973). They have been reported to have toxic, mutagenic, carcinogenic, teratogenic and endocrine-disrupting activities in several organisms (Dillingham & Autian, 1973; Gesler, 1973; Koch et al., 2003; Krauskopf, 1973; Phale et al., 2007; Quan et al., 2005; Rubin & Jaeger, 1973).
Micro-organisms present in the environment have evolved and adapted to degrade these compounds as the sole source of carbon and energy. With respect to phthalate isomers, the metabolic pathways and enzymes involved in the degradation of phthalate and terephthalate have been studied in greater detail than those of isophthalate (Chatterjee & Dutta, 2003; Eaton, 2001; Eaton & Ribbons, 1982; Keyser et al., 1976; Phale et al., 2007; Quan et al., 2005; Shigematsu et al., 2003; Vamsee-Krishna et al., 2006; Vamsee-Krishna & Phale, 2008; Wang et al., 1995, 2003). There are very few reports that describe the utilization of all three phthalate isomers as the carbon source by a single microbial strain (Vamsee-Krishna et al., 2006; Vamsee-Krishna & Phale, 2008; Wang et al., 1995). The first key step involved in the bacterial degradation of phthalate isomers is the double hydroxylation of the aromatic ring by the respective phthalate dioxygenase to yield a cis-dihydrodiol intermediate, which is further metabolized to aliphatic intermediates of the central carbon cycle via 3,4-dihydroxybenzoate (3,4-DHB) (Ballou & Batie, 1988; Batie et al., 1987; Schlafli et al., 1994; Tarasev & Ballou, 2005; Vamsee-Krishna et al., 2006).
Besides being toxic, phthalate, isophthalate and terephthalate are also reported to inhibit glutamate dehydrogenase (GDH) competitively (Caughey et al., 1957). The inter-proton distance between two carboxyl groups of isophthalate and glutamate is 7.45 Å (0.745 nm), which makes isophthalate a potent competitive inhibitor of GDH compared with phthalate and terephthalate (Caughey et al., 1957). Isophthalic acid and its derivatives have been reported to inhibit NAD-dependent GDH (NAD-GDH) from bovine, fungal, yeast and pea plant sources (Boots et al., 1976; Caughey et al., 1957; Cunliffe et al., 1983; Rogers et al., 1972; Stevens et al., 1989), as well as NADP-dependent GDH (NADP-GDH) from Aspergillus niger (Noor & Punekar, 2005).
GDH (EC 1.4.1.2-4) plays a crucial role at the crossroads of carbohydrate and amino acid metabolism. It catalyses the reductive amination of -ketoglutarate (-KG) to glutamate (anabolic reaction), the oxidative deamination of glutamate to -KG (catabolic reaction) and shows specificity to NAD or NADP, or both (Hudson & Daniel, 1993). NAD-GDH is involved in the catabolic, and NADP-GDH in the anabolic reaction of glutamate metabolism. NADP- and NAD-GDH are induced by NH3 and glutamate, respectively (Hudson & Daniel, 1993; Lu & Abdelal, 2001). The induction of different forms of GDH has been shown in many organisms under conditions such as salt, cold, trophic and environmental stress, and they have been found to be either stable at higher salt concentrations and extreme temperatures, or to have varying affinity for substrates (Bonete et al., 2003; Camardella et al., 2002; Moyano et al., 1992).
Pseudomonas aeruginosa strain PP4 and Pseudomonas sp. strain PPD degrade all three isomers of phthalate, while Acinetobacter lwoffii strain ISP4 degrades isophthalate alone as the sole source of carbon and energy (Vamsee-Krishna et al., 2006). The degradative pathways of phthalate isomers have been elucidated by performing various metabolic studies (Vamsee-Krishna et al., 2006). The interesting question is, since it is known that isophthalate acts as a competitive inhibitor of GDH, how are these bacterial strains able to degrade these compounds as the sole source of carbon and energy? We hypothesize that the GDH from these strains is insensitive or less sensitive to inhibition by isophthalate. Therefore, it was interesting to study various properties of GDH from these strains when grown on different carbon sources. The results obtained suggest that in strains PP4 and PPD, external supplementation with -KG, glutamate or glutamate-family amino acids at millimolar concentrations promotes faster growth on isophthalate, and carbon source-dependent induction of different forms of NADP-GDH was observed. NADP-GDH produced in the presence of isophthalate was less sensitive to isophthalate inhibition than NADP-GDH from glucose-grown cells. However, in strain ISP4, glutamate-family amino acids failed to promote faster growth on isophthalate, and a single form of NADP-GDH with a threefold higher activity than that of 2x yeast extract-tryptone broth (2YT)-grown cells was observed. The carbon source-dependent presence of different forms of GDH or an increase in its levels (activity) might help to overcome the inhibitory effect, thus allowing cells to utilize isophthalate as the carbon source.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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-ketoglutarate, glutamate, EDTA, glycine, acrylamide, N,N'-methylene-bis-acrylamide, N,N,N',N'-tetramethylethylenediamine (TEMED), m-hydroxybenzoate (mHB), p-hydroxybenzoate (pHB) and salicylate were purchased from Sigma-Aldrich. All other chemicals used were of analytical grade and purchased locally.
Bacterial strains and growth conditions.
P. aeruginosa strain PP4, Pseudomonas strain PPD and A. lwoffii strain ISP4, capable of degrading phthalate isomers as the carbon source and isolated from soils by enrichment culture, were used in the present study (Vamsee-Krishna et al., 2006). Cultures were grown in 150 ml mineral salt medium (MSM) (Basu et al., 2003) in 500 ml baffled Erlenmeyer flasks at 30 °C on a rotary shaker (200 r.p.m.). The medium was supplemented with either aromatic compounds (0.1 %) such as phthalate isomers (o-, m-, and p-)hydroxybenzoates and benzoate, or aromatics (0.1 %) plus -KG, glutamate- or non-glutamate-family amino acids (1 mM). Ammonium nitrate (1 g l–1, 0.1 %) was used as the nitrogen source. Alternatively, strains PP4 and PPD were grown on MSM supplemented with either glucose (0.25 %) or glutamate (10 mM), while strain ISP4 was grown on 2x yeast extract-tryptone broth (2YT; composition per litre of distilled water: yeast extract, 10 g; tryptone, 16 g; NaCl, 5 g) (Vamsee-Krishna et al., 2006). Cells grown on the respective carbon sources were used as an inoculum (2 ml per 150 ml MSM). Growth was monitored spectrophotometrically (Perkin Elmer Lambda 35) at 540 nm.
Preparation of cell-free extracts.
Cells grown to late-exponential phase were harvested (12 000 g for 15 min at 4 °C), washed twice and suspended (1 g wet weight in 4 ml) in ice-cold HEPES- NaOH buffer (20 mM, pH 8.5) containing EDTA (1 mM) and NaCl (100 mM) (Lu & Abdelal, 2001). Cells were disrupted on ice with five cycles of 20 pulses each (1 s pulse, 1 s interval, cycle duration 40 s, output 11–12 W with a 5 min interval between two cycles) using an Ultrasonic processor (model GE130). The cell lysate was centrifuged at 40 000 g for 30 min, and the clear supernatant obtained was referred to as cell-free extract and used for monitoring GDH activity. Protein was estimated by the method of Bradford (1976) using BSA as standard.
Activity staining of GDH.
Activity staining was performed to detect the different forms of GDH from cells grown on various carbon sources (Bellion & Tan, 1984). In brief, native PAGE (7.5 %) was performed at a constant current of 4 mA at 4 °C with an appropriate amount of protein (Laemmli, 1970). After electrophoresis, the gel was washed and equilibrated for 15 min with ice-cold HEPES-NaOH buffer (100 mM, pH 7.5) followed by incubation in activity staining solution (10 ml) containing glutamate (100 mM), NADP or NAD (0.2 mM), nitroblue tetrazolium (2.5 mg), phenazine methosulphate (2.5 mg) and HEPES-NaOH (100 mM, pH 7.5) at 25 °C until bands were distinctly visible. The staining reaction was terminated by soaking the gel in acetic acid (7.5 %) for a few minutes followed by extensive washing with distilled water.
Enzyme assay, inhibition and thermal stability of GDH.
The activity of GDH was monitored as the reductive amination of -KG by measuring the rate of disappearance of NADPH or NADH at 340 nm, spectrophotometrically (Lu & Abdelal, 2001). The reaction mixture (1 ml) contained -KG (10 mM), ammonium chloride (10 mM), NADPH or NADH (0.1 mM), appropriate amounts of cell-free extract and HEPES-NaOH (100 mM, pH 8.5) buffer. The activity was expressed as nanomoles of NADPH or NADH consumed per minute. Specific activities were defined as nmol min–1 (mg protein)–1.
To study inhibition, activity was monitored in the presence of different concentrations of inhibitors such as phthalate isomers, (o-, m-, p-) hydroxybenzoates and benzoate. The residual activity (%) was calculated by taking NAD- or NADP-GDH activity in the absence of inhibitor as 100 %.
To monitor the thermal stability of NADP-GDH, the cell-free extracts prepared from cells grown on either aromatics (0.1 %) or glucose (0.25 %) were incubated in the presence or absence of known GDH stabilizers such as -KG (1 mM) or glutamate (10 mM) at 60 °C for different times (5, 10, 20 and 30 min). The mixtures were centrifuged (40 000 g for 30 min) and the residual activity from the supernatant was measured. Activity at 0 min was taken as 100 %, and cell-free extracts without heat treatment were used as controls.
All experiments described were performed at least three times with readings in triplicate using appropriate controls. The SD observed was in the range of 3–8 %. The trends observed in activity-staining profiles were identical and the best profiles are shown.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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). A. lwoffii strain ISP4 grows on isophthalate, benzoate and 2YT, but fails to grow on glutamate or glucose (Vamsee-Krishna et al., 2006). Growth profiles of these strains on various carbon sources in the presence or absence of -KG or glutamate (1 mM) are shown in Fig. 1. Strain ISP4 utilized isophthalate very rapidly compared with strains PP4 and PPD.
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48 h (Fig. 1a
). However, on isophthalate plus glutamate or isophthalate plus -KG (a precursor of glutamate), cells entered stationary phase by 34 and 28 h, respectively. Glutamate alone at 1 mM concentration failed to support growth (Fig. 1a). This observation suggests that -KG or glutamate promotes faster growth on isophthalate (Fig. 1a). Supplementing isophthalate medium with glutamate-family amino acids such as glutamine, arginine or proline also promoted faster growth. However, such an effect was not observed with non-glutamate-family amino acids such as glycine and lysine (data not shown). A similar effect was observed with cultures grown on phthalate plus glutamate, terephthalate plus glutamate (growth profiles not shown) and mHB plus glutamate (Fig. 1b); however, the effect was less prominent compared with isophthalate plus glutamate. No significant difference in the growth profiles was observed when cells were grown on glucose, benzoate or pHB (Fig. 1b, c and data not shown, respectively) in the presence or absence of glutamate. These results suggest that the effect is significant for isophthalate plus glutamate-family amino acids.
In Pseudomonas strain PPD, supplementing isophthalate- or mHB-containing media with glutamate or -KG promoted faster growth compared with aromatics alone (Fig. 1d, e). However, the observed difference was less significant compared with strain PP4. No appreciable effect of glutamate supplementation was observed on the growth profiles in the presence of phthalate and terephthalate (growth profiles not shown). Strain PPD failed to show a clear difference between the growth profiles of isophthalate plus glutamate- or non-glutamate-family amino acids (data not shown). The growth profiles on glucose, benzoate and pHB in the presence or absence of glutamate were similar (Fig. 1f, e and data not shown, respectively).
Interestingly, A. lwoffii strain ISP4 did not show any effect on growth in the presence or absence of -KG, glutamate- or non-glutamate-family amino acids (Fig. 1g–i).
Carbon source-dependent forms of GDH
Late-exponential-phase cells showed a higher activity of GDH compared with early exponential-phase cells; hence, late-exponential-phase cells were used for this study. The activity staining profiles of NAD- and NADP-GDH from cells grown on various carbon sources are shown in Fig. 2. In strain PP4, GDH preparations from cells grown on isophthalate, phthalate, terephthalate or mHB in the presence or absence of glutamate (1 mM) showed a single NADP-GDH activity band with a lower electrophoretic mobility on native PAGE, referred to as GDHI. However, cells grown on glucose, glucose plus glutamate (1 mM), glutamate (10 mM) alone, pHB or benzoate showed a higher-mobility NADP-GDH activity band, referred to as GDHII (Fig. 2a). These results indicate that strain PP4 has two different forms of NADP-GDH. In strain PPD, the GDH preparation from cells grown on isophthalate, phthalate, terephthalate and mHB in the presence or absence of glutamate (1 mM) showed a single NADP-GDH activity band with a lower electrophoretic mobility, referred to as GDHA, while the preparation from glucose, glucose plus glutamate (1 mM) or glutamate (10 mM) alone showed a higher mobility NADP-GDH activity band, referred to as GDHB (Fig. 2b). Benzoate-grown PPD cells showed a staining band with the highest mobility (referred to as GDHC). Interestingly, cells grown on pHB showed two activity staining bands that corresponded to GDHB and GDHC (Fig. 2b). These results suggest that strain PPD has three different forms of NADP-GDH. Incubating cell-free extracts of glucose-grown cells of PP4 or PPD with isophthalate, or mixing and incubating cell-free extracts from glucose- and isophthalate-grown cells, did not affect the observed mobility pattern (data not shown), thus ruling out the possibility of enzyme modification. In strain ISP4, irrespective of the carbon source, a single NADP-GDH activity band, referred to as GDHP, was observed. However, the staining intensity was significantly higher for cells grown on aromatics than for those grown on 2YT (Fig. 2c).
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), suggesting that NAD- and NADP-GDH are different and do not show dual specificity for the coenzymes.
Carbon source-dependent activity and inhibition studies of GDH
Table 1 and Fig. 3 depict the specific activities and inhibition profiles of NAD- and NADP-GDHs measured from the cell-free extracts of strains PP4, PPD and ISP4 grown on different carbon sources. In all three strains (i) irrespective of the aromatic carbon source, cell-free extracts showed the activity of NADP-GDH only, while cells grown on glucose (0.25 %), glutamate (10 mM) or 2YT showed activities of both NADP- and NAD-GDH (Table 1); (ii) isophthalate at 1 mM inhibited GDHI, GDHA and GDHP (60–70 %), while phthalate and terephthalate did not inhibit these enzymes (Fig. 3a–c). Other compounds such as o-, m- and p-hydroxybenzoates and benzoate also failed to show any inhibition, even at 10 mM concentration (data not shown); (iii) irrespective of the carbon source, NADP-GDH showed inhibition with isophthalate alone (Fig. 3d–f); (iv) isophthalate failed to inhibit NAD-GDH (Table 1); and (v) effectors such as ATP, ADP, AMP and GTP (50 µM) failed to show any effect on NADP-GDH activity (data not shown).
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); (ii) compared with NADP-GDH, the activity of NAD-GDH from isophthalate plus glutamate (1 mM) -grown cells was either low (25-fold less in PP4) or absent (PPD) (Table 1); and (iii) GDHII, GDHB and GDHC were more susceptible to inhibition by isophthalate (50–65 % at 1 mM and 90 % at 10 mM) than GDHI and GDHA (25–30 % at 1 mM and 65–70 % at 10 mM; Table 1, Fig. 3d, e). The initial rates of inhibition of GDHI and GDHA were low compared with GDHII, GDHB and GDHC (Fig. 3d).
In strain ISP4, isophthalate-grown cells showed a threefold higher activity of GDHP compared with 2YT-grown cells; this observation was supported by the activity staining data (Fig. 2c). The activity of GDHP from isophthalate-, isophthalate plus glutamate- (1 mM), benzoate- and 2YT-grown cells showed 52–58 % inhibition at 1 mM and 80 % at 10 mM isophthalate (Fig. 3f).
Thermal stability of GDH
Time-dependent changes in the activity of NADP-GDH at 60 °C are shown in Fig. 4. In strain PP4, GDHI from isophthalate- and mHB-grown cells retained 70 and 90 % of its activity, respectively. However, GDHII lost activity completely within 10 min (Fig. 4a), while the addition of glutamate (10 mM), -KG (1 mM) or isophthalate (1 mM) failed to protect or stabilize the activity (data not shown). In strains PPD and ISP4, isophthalate-, glucose-, 2YT- or mHB-grown cells retained 100 % of the activity of NADP-GDH, while PPD cells grown on pHB and benzoate showed 25 and 40 % loss of activity, respectively (Fig. 4b, c).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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). The results demonstrate that the exogenous addition of -KG or glutamate-family amino acids to PP4 and PPD cultures led to faster growth on isophthalate; however, such an effect was not observed in strain ISP4 (Fig. 1). This could be mediated through rapid uptake of -KG or glutamate-family amino acids, leading to an increase in the intracellular concentration of these compounds, thus lowering the effective inhibition of GDHI and GDHA by isophthalate. To the best of our knowledge, these growth-promoting effects are unique and have not been reported so far. Interestingly, in strain PP4, exogenous addition of glutamate promoted faster growth on mHB and showed a twofold higher activity of GDHI compared with isophthalate-grown cells, while pHB-grown cells showed a higher activity of GDHII (Fig. 1, Table 1). These results are intriguing; one possible explanation is that although mHB and pHB have the same functional groups (-OH and -COOH), their positions are different on the aromatic ring. In that respect, mHB is structurally closer to isophthalate than pHB.
Depending on the carbon and nitrogen sources, different forms of GDH [NADP-, NAD- or NAD(P)-] have been reported from Clostridium symbiosum (Syed et al., 1991), Laccaria bicolor (Garnier et al., 1997), Escherichia coli (Maurizi & Rasulova, 2002), P. aeruginosa (Smits et al., 1984), Sulfolobus solfataricus (Schinkinger et al., 1991) and Salinibacter ruber (Bonete et al., 2003). The induction of NAD-, NADP- or NAD(P)-GDH has also been reported under varying environmental conditions such as salt (Bonete et al., 1990, 2003), temperature (Camardella et al., 2002) and nitrogen source (Abrahams & Abratt, 1998; Brown et al., 1973; LeJohn & McCrea, 1968). In Neisseria meningitidis, transcriptional analysis has shown carbon source-dependent expression of gdhA, leading to a difference in the growth of the strain (Pagliarulo et al., 2004).
In strains PP4, PPD and ISP4, both NAD- and NADP-GDHs were detected (Table 1, Fig. 2). With fixed nitrogen and varying carbon sources, two forms of NADP-GDH, GDHI and GDHII, in strain PP4, and three forms of NADP-GDH, GDHA, GDHB and GDHC, in strain PPD, were detected, and showed differences in thermal stability, activity staining pattern and susceptibility to inhibition by isophthalate (Table 1, Figs 2–4). To the best of our knowledge, this is the first biochemical report of the carbon source-dependent presence of different forms of NADP-GDH in a bacterial system. Carbon source-dependent induction of two isozymes (NADP-GDH) has been reported in Saccharomyces cerevisiae; GDH1 is induced when cells are grown either on glucose or ethanol, while GDH2 is induced on ethanol only (Deluna et al., 2001). The co-ordinated expression of these enzymes with different carbon sources, and the varying allosteric properties and rates of -KG utilization account for the role of isozymes of NADP-GDH. Similarly, in the green alga Chlamydomonas reinhardtii, the presence of three different isozymes of NAD(P)-GDHs, GDH1, GDH2 and GDH3, is induced under dark, CO2 plus light and light phases, respectively (Moyano et al., 1992; Muñoz-Blanco et al., 1989).
NADP-GDH from strains PP4, PPD and ISP4 was inhibited by isophthalate (75–80 % at 10 mM). Similar results have been observed for NADP-GDH from A. niger (Noor & Punekar, 2005). Interestingly, no inhibitory effect of isophthalate was observed with NAD-GDH from the three strains (Table 1); this is in contrast to bovine NAD-GDH, which is susceptible to inhibition by isophthalate, terephthalate and phthalate (Caughey et al., 1957). The activity of GDH has been reported to be modulated (activation or deactivation) by nucleotides such as ATP, ADP, AMP and GTP (Bonete et al., 2003; LeJohn & Jackson, 1968; Smith et al., 2001, 2002). However, no such modulatory effect was observed with NADP-GDH from the three strains in this study (data not shown). Mixing and incubation of cell-free extracts of isophthalate- and glucose-grown cells did not vary the electrophoretic mobility of GDH, suggesting that post-translational protein modification(s) is/are absent, and that the forms of the enzymes are indeed different, as seen in Fig. 2.
The difficulties in the successful isolation of isophthalate-degrading strains from the environment could be due to the fact that isophthalate acts as a potent competitive inhibitor of GDH, which interlinks carbon and nitrogen metabolism (Boots et al., 1976; Caughey et al., 1957; Cunliffe et al., 1983; Rogers et al., 1972; Stevens et al., 1989). The present study demonstrates that although GDH is inhibited by isophthalate, strains PP4, PPD and ISP4 have adopted different strategies, such as carbon source-dependent modulation of forms of NADP-GDH, for the effective utilization of isophthalate, and that they thrive in the environment. Strains PP4 and PPD when grown on isophthalate produce a form of NADP-GDH that is less sensitive to inhibition by isophthalate, while cells grown on glucose produce the other form, which is more sensitive to isophthalate inhibition. In strain ISP4, a single form of NADP-GDH was present, whose activity was increased threefold when grown on isophthalate; such modulation of enzymes helps to counteract the inhibitory effect of the carbon source, isophthalate. Characterization of these enzymes for their molecular and kinetic properties may help in the construction of novel strains suitable for effective bioremediation of recalcitrant aromatic compounds that interfere with the normal metabolic pathways of the cell.
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ACKNOWLEDGEMENTS |
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Edited by: H. L. Drake
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REFERENCES |
|---|
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Ballou, D. & Batie, C. (1988). Phthalate oxygenase, a Rieske iron-sulfur protein from Pseudomonas cepacia. Prog Clin Biol Res 274, 211–226.[Medline]
Basu, A., Dixit, S. S. & Phale, P. S. (2003). Metabolism of benzyl alcohol via catechol ortho-pathway in methylnaphthalene-degrading Pseudomonas putida CSV86. Appl Microbiol Biotechnol 62, 579–585.[CrossRef][Medline]
Batie, C. J., LaHaie, E. & Ballou, D. P. (1987). Purification and characterization of phthalate oxygenase and phthalate oxygenase reductase from Pseudomonas cepacia. J Biol Chem 262, 1510–1518.
Bellion, E. & Tan, F. (1984). NADP-dependent glutamate dehydrogenase from a facultative methylotroph, Pseudomonas sp. strain AM1. J Bacteriol 157, 435–439.
Bonete, M. J., Camacho, M. L. & Cadenas, E. (1990). Analysis of the kinetic mechanism of halophilic NADP-dependent glutamate dehydrogenase. Biochim Biophys Acta 1041, 305–310.[CrossRef][Medline]
Bonete, M. J., Perez-Pomares, F., Diaz, S., Ferrer, J. & Oren, A. (2003). Occurrence of two different glutamate dehydrogenase activities in the halophilic bacterium Salinibacter ruber. FEMS Microbiol Lett 226, 181–186.[CrossRef][Medline]
Boots, S. G., Franklin, M. A., Dunlavey, B., Costello, J., Lipsitz, C., Boots, M. R. & Rogers, K. S. (1976). Synthesis of 5-substituted isophthalic acids and competitive inhibition studies with bovine liver glutamate dehydrogenase. Proc Soc Exp Biol Med 151, 316–320.[CrossRef][Medline]
Bradford, M. M. (1976). A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72, 248–254.[CrossRef][Medline]
Brown, C. M., Macdonald-Brown, D. S. & Stanley, S. O. (1973). The mechanisms of nitrogen assimilation in pseudomonads. Antonie Van Leeuwenhoek 39, 89–98.[CrossRef][Medline]
Camardella, L., Di Fraia, R., Antignani, A., Ciardiello, M. A., di Prisco, G., Coleman, J. K., Buchon, L., Guespin, J. & Russell, N. J. (2002). The Antarctic Psychrobacter sp. TAD1 has two cold-active glutamate dehydrogenases with different cofactor specificities. Characterisation of the NAD+-dependent enzyme. Comp Biochem Physiol A Mol Integr Physiol 131, 559–567.[CrossRef][Medline]
Caughey, W. S., Hellerman, L. & Smiley, J. D. (1957). L-Glutamic acid dehydrogenase; structural requirements for substrate competition; effect of thyroxine. J Biol Chem 224, 591–607.
Chatterjee, S. & Dutta, T. K. (2003). Metabolism of butyl benzyl phthalate by Gordonia sp. strain MTCC 4818. Biochem Biophys Res Commun 309, 36–43.[CrossRef][Medline]
Cunliffe, D., Leason, M., Parkin, D. & Lea, P. J. (1983). The inhibition of glutamate dehydrogenase by derivatives of isophthalic acid. Phytochemistry 22, 1357–1360.[CrossRef]
Deluna, A., Avendano, A., Riego, L. & Gonzalez, A. (2001). NADP-glutamate dehydrogenase isoenzymes of Saccharomyces cerevisiae. Purification, kinetic properties, and physiological roles. J Biol Chem 276, 43775–43783.
Dillingham, E. O. & Autian, J. (1973). Teratogenicity, mutagenicity, and cellular toxicity of phthalate esters. Environ Health Perspect 3, 81–89.[Medline]
Eaton, R. W. (2001). Plasmid-encoded phthalate catabolic pathway in Arthrobacter keyseri 12B. J Bacteriol 183, 3689–3703.
Eaton, R. W. & Ribbons, D. W. (1982). Metabolism of dimethylphthalate by Micrococcus sp. strain 12B. J Bacteriol 151, 465–467.
Garnier, A., Berredjem, A. & Botton, B. (1997). Purification and characterization of the NAD-dependent glutamate dehydrogenase in the ectomycorrhizal fungus Laccaria bicolor (Maire) orton. Fungal Genet Biol 22, 168–176.[CrossRef][Medline]
Gesler, R. M. (1973). Toxicology of di-2-ethylhexyl phthalate and other phthalic acid ester plasticizers. Environ Health Perspect 3, 73–79.[CrossRef][Medline]
Hudson, R. C. & Daniel, R. M. (1993). L-Glutamate dehydrogenases: distribution, properties and mechanism. Comp Biochem Physiol B 106, 767–792.[CrossRef][Medline]
Jaeger, R. J. & Rubin, R. J. (1973). Extraction, localization, and metabolism of di-2-ethylhexyl phthalate from PVC plastic medical devices. Environ Health Perspect 3, 95–102.[Medline]
Keyser, P., Pujar, B. G., Eaton, R. W. & Ribbons, D. W. (1976). Biodegradation of the phthalates and their esters by bacteria. Environ Health Perspect 18, 159–166.[Medline]
Koch, H. M., Drexler, H. & Angerer, J. (2003). An estimation of the daily intake of di(2-ethylhexyl)phthalate (DEHP) and other phthalates in the general population. Int J Hyg Environ Health 206, 77–83.[CrossRef][Medline]
Krauskopf, L. G. (1973). Studies on the toxicity of phthalates via ingestion. Environ Health Perspect 3, 61–72.[Medline]
Laemmli, U. K. (1970). Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227, 680–685.[CrossRef][Medline]
LeJohn, H. B. & Jackson, S. (1968). Allosteric interactions of a regulatory nicotinamide adenine dinucleotide-specific glutamate dehydrogenase from Blastocladiella. A molecular model for the enzyme. J Biol Chem 243, 3447–3457.
LeJohn, H. B. & McCrea, B. E. (1968). Evidence for two species of glutamate dehydrogenases in Thiobacillus novellus. J Bacteriol 95, 87–94.
Lu, C. D. & Abdelal, A. T. (2001). The gdhB gene of Pseudomonas aeruginosa encodes an arginine-inducible NAD+-dependent glutamate dehydrogenase which is subject to allosteric regulation. J Bacteriol 183, 490–499.
Maurizi, M. R. & Rasulova, F. (2002). Degradation of L-glutamate dehydrogenase from Escherichia coli: allosteric regulation of enzyme stability. Arch Biochem Biophys 397, 206–216.[CrossRef][Medline]
Moyano, E., Cardenas, J. & Muñoz-Blanco, J. (1992). Purification and properties of three NAD(P)+ isozymes of L-glutamate dehydrogenase of Chlamydomonas reinhardtii. Biochim Biophys Acta 1119, 63–68.[CrossRef][Medline]
Muñoz-Blanco, J., Moyano, E. & Cárdenas, J. (1989). Glutamate dehydrogenase isozymes of Chlamydomonas reinhardtii. FEMS Microbiol Lett 61, 315–318.
Noor, S. & Punekar, N. S. (2005). Allosteric NADP-glutamate dehydrogenase from aspergilli: purification, characterization and implications for metabolic regulation at the carbon–nitrogen interface. Microbiology 151, 1409–1419.
Pagliarulo, C., Salvatore, P., De Vitis, L. R., Colicchio, R., Monaco, C., Tredici, M., Tala, A., Bardaro, M., Lavitola, A. & other authors (2004). Regulation and differential expression of gdhA encoding NADP-specific glutamate dehydrogenase in Neisseria meningitidis clinical isolates. Mol Microbiol 51, 1757–1772.[CrossRef][Medline]
Phale, P. S., Basu, A., Majhi, P. D., Deveryshetty, J., Vamsee-Krishna, C. & Shrivastava, R. (2007). Metabolic diversity in bacterial degradation of aromatic compounds. OMICS 11, 252–279.[CrossRef][Medline]
Quan, C. S., Liu, Q., Tian, W. J., Kikuchi, J. & Fan, S. D. (2005). Biodegradation of an endocrine-disrupting chemical, di-2-ethylhexyl phthalate, by Bacillus subtilis No. 66. Appl Microbiol Biotechnol 66, 702–710.[CrossRef][Medline]
Rogers, K. S., Boots, M. R. & Boots, S. G. (1972). Molecular interactions of six aromatic competitive inhibitors with bovine liver glutamate dehydrogenase. Biochim Biophys Acta 258, 343–350.[Medline]
Rubin, R. J. & Jaeger, R. J. (1973). Some pharmacologic and toxicologic effects of di-2-ethylhexyl phthalate (DEHP) and other plasticizers. Environ Health Perspect 3, 53–59.[CrossRef][Medline]
Schinkinger, M. F., Redl, B. & Stoffler, G. (1991). Purification and properties of an extreme thermostable glutamate dehydrogenase from the archaebacterium Sulfolobus solfataricus. Biochim Biophys Acta 1073, 142–148.[Medline]
Schlafli, H. R., Weiss, M. A., Leisinger, T. & Cook, A. M. (1994). Terephthalate 1,2-dioxygenase system from Comamonas testosteroni T-2: purification and some properties of the oxygenase component. J Bacteriol 176, 6644–6652.
Shigematsu, T., Yumihara, K., Ueda, Y., Numaguchi, M., Morimura, S. & Kida, K. (2003). Delftia tsuruhatensis sp. nov., a terephthalate-assimilating bacterium isolated from activated sludge. Int J Syst Evol Microbiol 53, 1479–1483.
Smith, T. J., Peterson, P. E., Schmidt, T., Fang, J. & Stanley, C. A. (2001). Structures of bovine glutamate dehydrogenase complexes elucidate the mechanism of purine regulation. J Mol Biol 307, 707–720.[CrossRef][Medline]
Smith, T. J., Schmidt, T., Fang, J., Wu, J., Siuzdak, G. & Stanley, C. A. (2002). The structure of apo human glutamate dehydrogenase details subunit communication and allostery. J Mol Biol 318, 765–777.[CrossRef][Medline]
Smits, R. A., Pieper, F. R. & van der Drift, C. (1984). Purification of NADP-dependent glutamate dehydrogenase from Pseudomonas aeruginosa and immunochemical characterization of its in vivo inactivation. Biochim Biophys Acta 801, 32–39.[Medline]
Stevens, L., Duncan, D. & Robertson, P. (1989). Purification and characterisation of NAD-glutamate dehydrogenase from Aspergillus nidulans. FEMS Microbiol Lett 48, 173–177.[Medline]
Syed, S. E., Engel, P. C. & Parker, D. M. (1991). Functional studies of a glutamate dehydrogenase with known three-dimensional structure: steady-state kinetics of the forward and reverse reactions catalysed by the NAD+-dependent glutamate dehydrogenase of Clostridium symbiosum. Biochim Biophys Acta 1115, 123–130.[Medline]
Tarasev, M. & Ballou, D. P. (2005). Chemistry of the catalytic conversion of phthalate into its cis-dihydrodiol during the reaction of oxygen with the reduced form of phthalate dioxygenase. Biochemistry 44, 6197–6207.[CrossRef][Medline]
Tepper, L. B. (1973). Phthalic acid esters – an overview. Environ Health Perspect 3, 179–182.[CrossRef][Medline]
Vamsee-Krishna, C. & Phale, P. S. (2008). Bacterial degradation of phthalate isomers and their esters. Indian J Microbiol 48, 19–34.[CrossRef]
Vamsee-Krishna, C., Mohan, Y. & Phale, P. S. (2006). Biodegradation of phthalate isomers by Pseudomonas aeruginosa PP4, Pseudomonas sp. PPD and Acinetobacter lwoffii ISP4. Appl Microbiol Biotechnol 72, 1263–1269.[CrossRef][Medline]
Wang, Y. Z., Zhou, Y. & Zylstra, G. J. (1995). Molecular analysis of isophthalate and terephthalate degradation by Comamonas testosteroni YZW-D. Environ Health Perspect 103, 9–12.
Wang, Y., Fan, Y. & Gu, J. D. (2003). Microbial degradation of the endocrine-disrupting chemicals phthalic acid and dimethyl phthalate ester under aerobic conditions. Bull Environ Contam Toxicol 71, 810–818.[CrossRef][Medline]
Received 9 July 2008;
revised 4 August 2008;
accepted 6 August 2008.
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), isophthalate (0.1 %) plus glutamate (1 mM, 
), isophthalate (0.1 %) plus 
) and glutamate alone (1 mM, 
). (b, e, h) Growth profiles on mHB (0.1 %, 
) and benzoate (0.1 %) plus glutamate (1 mM, 
). (d, e, f) Profiles of the inhibition of NADP-GDH by isophthalate from cells grown on different carbon sources: isophthalate (0.1 %, 
), pHB (0.1 %, 
), benzoate (0.1 %, x) and glucose (0.25 %, 
) or 2YT (
, dotted line) or 2YT (