Open AccessBiochemical and molecular characterization of α‐ketoisovalerate decarboxylase, an enzyme involved in the formation of aldehydes from amino acids by Lactococcus lactis
Author(s) -
Plaza Marta,
Fernández de Palencia Pilar,
Peláez Carmen,
Requena Teresa
Publication year - 2004
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2004.tb09778.x
Subject(s) - transamination , oxidative decarboxylation , decarboxylation , biochemistry , lactococcus lactis , enzyme , chemistry , amino acid , valine , oxidative deamination , stereochemistry , biology , lactic acid , bacteria , genetics , catalysis
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.