ISSN:
1574-6968
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
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 Mg2+, activity was observed in presence of other divalent cations such as Ca2+, Co2+ and Mn2+. 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1574-6968.2004.tb09778.x
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