title: Characterization of an oxaloacetate decarboxylase that belongs to the malic enzyme family.
abstract: The citM gene from Lactococcus lactis CRL264 was demonstrated to encode for an oxaloacetate decarboxylase. The enzyme exhibits high levels of similarity to malic enzymes (MEs) from other organisms. CitM was expressed in Escherichia coli, purified and its oxaloacetate decarboxylase activity was demonstrated by biochemical and genetic studies. The highest oxaloacetate decarboxylation activity was found at low pH in the presence of manganese, and the Km value for oxaloacetate was 0.52+/-0.03 mM. However, no malic activity was found for this enzyme. Our studies clearly show a new group of oxaloacetate decarboxylases associated with the citrate fermentation pathway in gram-positive bacteria. Furthermore, the essential catalytic residues were found to be conserved in all members of the ME family, suggesting a common mechanism for oxaloacetate decarboxylation.
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, (S2002LRK) Rosario, Argentina.
authors.forename: Pablo D
authors.initials: PD
authors.lastname: Sender
authors.forename: Mauricio G
authors.initials: MG
authors.lastname: Martín
authors.forename: Salvador
authors.initials: S
authors.lastname: Peirú
authors.forename: Christian
authors.initials: C
authors.lastname: Magni
mesh_terms: D000595:Amino Acid Sequence; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000235:genetics*; D020134:Catalytic Domain; D002412:Cations; D019343:Citric Acid / Q000737:chemistry; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D005285:Fermentation; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry; D013294:Lactococcus lactis / Q000201:enzymology; D008345:Manganese / Q000737:chemistry; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013696:Temperature; D013997:Time Factors
chemical_list: D002412:Cations; D019343:Citric Acid; D019344:Lactic Acid; D008345:Manganese; D002262:Carboxy-Lyases; C021916:oxaloacetate decarboxylase