HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Quezada, H. Articles by González, A. PubMed PubMed Citation Articles by Quezada, H. Articles by González, A. Agricola Articles by Quezada, H. Articles by González, A.

Specialization of the paralogue LYS21 determines lysine biosynthesis under respiratory metabolism in Saccharomyces cerevisiae

¹ Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-242, México DF 04510, México
² Laboratorio de Fisicoquímica e Ingeniería de Proteínas, Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, México DF 04510, México
³ Instituto Nacional de Cardiología, Departamento de Bioquímica, Tlalpan, México DF, México

Correspondence
Alicia González
amanjarr{at}ifc.unam.mx

In the yeast Saccharomyces cerevisiae, the first committed step of the lysine biosynthetic pathway is catalysed by two homocitrate synthases encoded by LYS20 and LYS21. We undertook a study of the duplicate homocitrate synthases to analyse whether their retention and presumable specialization have affected the efficiency of lysine biosynthesis in yeast. Our results show that during growth on ethanol, homocitrate is mainly synthesized through Lys21p, while under fermentative metabolism, Lys20p and Lys21p play redundant roles. Furthermore, results presented in this paper indicate that, in contrast to that which had been found for Lys20p, lysine is a strong allosteric inhibitor of Lys21p (K_i 0.053 mM), which, in addition, induces positive co-operativity for -ketoglutarate (-KG) binding. Differential lysine inhibition and modulation by -KG of the two isozymes, and the regulation of the intracellular amount of the two isoforms, give rise to an exquisite regulatory system, which balances the rate at which -KG is diverted to lysine biosynthesis or to other metabolic pathways. It can thus be concluded that retention and further biochemical specialization of the LYS20- and LYS21-encoded enzymes with partially overlapping roles contributed to the acquisition of facultative metabolism.