Pyruvate decarboxylase encoded by the PDC1 gene contributes, at least partially, to the decarboxylation of alpha-ketoisocaproate for isoamyl alcohol formation in Saccharomyces cerevisiae

Isoamyl alcohol is an important flavor component of yeast-fermented alcohol ic beverages. To identify the enzyme and gene involved in the decarboxylati on of alpha -ketoisocaproate (alpha -KIC) for isoamyl alcohol formation, th e enzyme was partially purified and analyzed by mass spectrometry. The pyru vate decarboxylase encoded by the PDC1 gene was considered a likely candida te enzyme. Genetic analysis showed that the activity of alpha -KIC decarbox ylase and production of isoamyl alcohol partially decreased in a pdc1 null mutant and increased in a transformant with a multi-copy plasmid carrying t he PDC1 gene. These results indicate that pyruvate decarboxylase encoded by the PDC1 gene contributes, at least partially, to the decarboxylation of a lpha -KIC for isoamyl alcohol formation.