Identification cloning and characterization of a branched-chain alpha-keto acid decarboxylase from Lactococcus lactis, involved in flavour formation

B.A. Smit, L. Meijer, W.J.M. Engels, J.T.M. Wouters, G. Smit

Research output: Contribution to journalArticleAcademicpeer-review

92 Citations (Scopus)

Abstract

The biochemical pathway for formation of branched-chain aldehydes, which are important flavor compounds derived from proteins in fermented dairy products, consists of a protease, peptidases, a transaminase, and a branched-chain ¿-keto acid decarboxylase (KdcA). The activity of the latter enzyme has been found only in a limited number of Lactococcus lactis strains. By using a random mutagenesis approach, the gene encoding KdcA in L. lactis B1157 was identified. The gene for this enzyme is highly homologous to the gene annotated ipd, which encodes a putative indole pyruvate decarboxylase, in L. lactis IL1403. Strain IL1403 does not produce KdcA, which could be explained by a 270-nucleotide deletion at the 3¿ terminus of the ipd gene encoding a truncated nonfunctional decarboxylase. The kdcA gene was overexpressed in L. lactis for further characterization of the decarboxylase enzyme. Of all of the potential substrates tested, the highest activity was observed with branched-chain ¿-keto acids. Moreover, the enzyme activity was hardly affected by high salinity, and optimal activity was found at pH 6.3, indicating that the enzyme might be active under cheese ripening conditions.
Original languageEnglish
Pages (from-to)303-311
JournalApplied and Environmental Microbiology
Volume71
Issue number1
DOIs
Publication statusPublished - 2005

Keywords

  • controlled gene-expression
  • complete genome sequence
  • gram-positive bacteria
  • indolepyruvate decarboxylase
  • pyruvate decarboxylase
  • enterobacter-cloacae
  • escherichia-coli
  • indole-3-acetic-acid biosynthesis
  • saccharomyces-cerevisiae
  • amino-acids

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