Purification, characterisation and cDNA sequencing of pyruvate decarboxylase from Zygosaccharomyces bisporus

Cells of the wild-type yeast strain Zygosaccharomyces bisporus CBS 702 form alpha-hydroxy ketones from aromatic amino acid precursors during fermentat ion, Pyruvate decarboxylase (PDC, E.C. 4.1.1.1), the key enzyme of this bio transformation catalysing the nonoxidative decarboxylation of pyruvate and other 2-oxo-acids, was purified and characterised. The active enzyme is hom otetrameric (alpha(4)) with a molecular mass of about 244 kDa, Activation o f PDC by its substrate pyruvate results in a sigmoidal dependence of the re action rate from substrate concentration (apparent K-m value 1.73 mM; Hill coefficient 2.10). A cDNA library was screened using a PCR-based procedure, and a 1856 bp cDNA of PDC was identified and sequenced. The cDNA encodes a polypeptide of 563 amino acid residues (monomeric unit), Sequence alignments demonstrate high homologies (> 80%) to PDC genes from Saccharomyces cerevisiae, Kluyveromyc es lactis and Kluyveromyces marxianus.