Biochemical and molecular characterization of α-ketoisovalerate decarboxylase, an enzyme involved in the formation of aldehydes from amino acids by Lactococcus lactis

• Published in: FEMS microbiology letters Vol. 238; no. 2; pp. 367 - 374
• Main Authors: de la Plaza, Marta, Fernández de Palencia, Pilar, Peláez, Carmen, Requena, Teresa
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15.09.2004; Blackwell
• Subjects: Aldehydes - metabolism; Amino acid catabolism; Amino Acids - metabolism; Bacteriology; Biological and medical sciences; Carboxy-Lyases - genetics; Carboxy-Lyases - isolation & purification; Carboxy-Lyases - metabolism; cheese ripening; flavor compounds; Fundamental and applied biological sciences. Psychology; goat cheese; lactic acid bacteria; Lactococcus lactis; Lactococcus lactis - enzymology; Lactococcus lactis - genetics; Leucine - biosynthesis; Metabolism. Enzymes; Microbiology; Open Reading Frames; Pyruvates - metabolism; Valine - biosynthesis; α-Ketoisovalerate decarboxylase; Lactococcus lactis; α-Ketoisovalerate decarboxylase; Amino acid catabolism; Lactic acid bacteria; Decarboxylase; Enzyme; Escherichia coli; α-Keloisovalerate decarboxylase; Lyases; Aldehyde; Gene expression; Streptococcaceae; Lactococcus lactic; Carbon-carbon lyases; Carboxy-lyases; Aminoacid; Bacteria; Micrococcales; Catabolism; Kinetics; Enterobacteriaceae
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2004.07.057

In this paper, we report for the first time on the identification, purification, and characterization of the α-ketoisovalerate decarboxylase from Lactococcus lactis, a novel enzyme responsible for the decarboxylation into aldehydes of α-keto acids derived from amino acid transamination. The kivd gene consisted of a 1647 bp open reading frame encoding a putative peptide of 61 kDa. Analysis of the deduced amino acid sequence indicated that the enzyme is a non-oxidative thiamin diphosphate (ThDP)-dependent α-keto acid decarboxylase included in the pyruvate decarboxylase group of enzymes. The active enzyme is a homo-tetramer that showed optimum activity at 45 °C and at pH 6.5 and exhibited an inhibition pattern typical for metal-dependant enzymes. In addition to Mg 2+, activity was observed in presence of other divalent cations such as Ca 2+, Co 2+ and Mn 2+. The enzyme showed the highest specific activity (80.7 U mg −1) for α-ketoisovalerate, an intermediate metabolite in valine and leucine biosynthesis. On the other side, decarboxylation of indole-3-pyruvate and pyruvate only could be detected by a 100-fold increase in the enzyme concentration present in the reaction.