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A low-M_r lipase activation factor cooperating with lipase modulator protein LimL in Pseudomonas sp. strain 109

Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan¹
Department of Plant Protection, National Institute of Fruit Tree Science, 2-1 Fujimoto, Tsukuba, Ibaraki 305-8605, Japan²

Author for correspondence: Takuya Nihira. Tel: +81 6 6879 7433. Fax: +81 6 6879 7432. e-mail: nihira{at}biochem.bio.eng.osaka-u.ac.jp

Pseudomonas sp. strain 109 produces a unique lipase (LipL) which efficiently catalyses intramolecular transesterification of -hydroxyesters to form macrocyclic lactones. In vivo production of enzymically active LipL requires lipase modulator protein (LimL), which functions as a molecular chaperone for the correct folding of LipL. However, previous work has shown that LipL forms a tight complex with LimL in vitro and the resulting LipL–LimL complex is only partially active, suggesting an additional mechanism that facilitates the dissociation of the complex to form enzymically active LipL. In the present work, a low-M_r compound (lipase activation factor, LAF) was found in Pseudomonas sp. strain 109 that when added to the LipL–LimL complex resulted in the activation of LipL. Ca²⁺ ions also enhanced lipase activity, but the instantaneous activation by Ca²⁺ was different from the gradual and time-dependent activation by LAF, indicating the novel nature of this compound. LAF passed through an ultrafiltration membrane with an M_r cut-off of 3000 and showed an apparent M_r of 330±30 on Superdex Peptide gel-filtration chromatography. Treatment of the LipL–LimL complex with LAF liberated free active LipL, indicating that LAF was necessary to dissociate the LipL–LimL complex.

Keywords: Pseudomonas, lactonizing lipase, lipase activation factor, lipase modulator protein

Abbreviations: LAF, lipase activation factor