title: ALT1-encoded alanine aminotransferase plays a central role in the metabolism of alanine in Saccharomyces cerevisiae.
abstract: In the yeast Saccharomyces cerevisiae, the paralogous genes ALT1 and ALT2 have been proposed to encode alanine aminotransferase isozymes. Although in other microorganisms this enzyme constitutes the main pathway for alanine biosynthesis, its role in S. cerevisiae had remained unclear. Results presented in this paper show that under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism, constituting the first example of an alanine aminotransferase that simultaneously carries out both functions. Conversely, under fermentative conditions, it plays a catabolic role and alanine is mainly synthesized through an alternative pathway. It can thus be concluded that ALT1 has functions in alanine biosynthesis and utilization or only alanine utilization under respiratory and fermentative conditions, respectively. ALT2 expression was repressed under all tested conditions, suggesting that Alt2p biosynthesis is strictly controlled and only allowed to express under peculiar physiological conditions.
authors.affiliation: Departamento de Genetica Molecular, Instituto de Fisiologia Celular, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-242, Mexico City, D.F. 04510, Mexico.
authors.forename: Florencia
authors.initials: F
authors.lastname: García-Campusano
authors.forename: Víctor-Hugo
authors.initials: VH
authors.lastname: Anaya
authors.forename: Luis
authors.initials: L
authors.lastname: Robledo-Arratia
authors.forename: Héctor
authors.initials: H
authors.lastname: Quezada
authors.forename: Hugo
authors.initials: H
authors.lastname: Hernández
authors.forename: Lina
authors.initials: L
authors.lastname: Riego
authors.forename: Alicia
authors.initials: A
authors.lastname: González
mesh_terms: D000409:Alanine / Q000378:metabolism*; D000410:Alanine Transaminase / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D003470:Culture Media; D029701:Saccharomyces cerevisiae Proteins; D000410:Alanine Transaminase; D000409:Alanine