US EPA

7054984 

Journal Article 

Pyruvate decarboxylase: An indispensable enzyme for growth of Saccharomyces cerevisiae on glucose 

Flikweert, MT; Vanderzanden, L; Janssen, W; Steensma, HY; Vandijken, JP; Pronk, JT; , 

1996 

1 

Yeast
ISSN: 0749-503X 

JOHN WILEY & SONS LTD 

W SUSSEX 

247-257 

8904337 

WOS:A1996TY30700007 

In Saccharomyces cerevisiae, the structural genes PDC1, PDC5 and PDC6 each encode an active pyruvate decarboxylase. Replacement mutations in these genes were introduced in a homothallic wild-type strain, using the dominant marker genes APT1 and Ti5ble. A pyruvate-decarboxylase-negative (Pdc(-)) mutant lacking all three PDC genes exhibited a three-fold lower growth rate in complex medium with glucose than the isogenic wild-type strain. Growth in batch cultures on complex and defined media with ethanol was not impaired in Pdc(-) strains. Furthermore, in ethanol-limited chemostat cultures, the biomass yield of Pdc(-) and wild-type S. cerevisiae were identical. However, Pdc(-) S. cerevisiae was unable to grow in batch cultures on a defined mineral medium with glucose as the sole carbon source. When aerobic, ethanol-limited chemostat cultures (D = 0 . 10 h(-1)) were switched to a feed containing glucose as the sole carbon source, growth ceased after approximately 4 h and, consequently, the cultures washed out. The mutant was, however, able to grow in chemostat cultures on mixtures of glucose and small amounts of ethanol or acetate (5% on a carbon basis). No growth was observed when such cultures were used to inoculate batch cultures on glucose. Furthermore, when the mixed-substrate cultures were switched to a feed containing glucose as the sole carbon source, wash-out occurred. It is concluded that the mitochondrial pyruvate dehydrogenase complex cannot function as the sole source of acetyl-CoA during growth of S. cerevisiae on glucose, neither in batch cultures nor in glucose-limited chemostat cultures.