Extramitochondrial citrate synthase activity in bakers' yeast.

We isolated the gene for citrate synthase (citrate oxaloacetate lyase; EC 4.1.3.7) from Saccharomyces cerevisiae and ablated it by inserting the yeast LEU2 gene within its reading frame. This revealed a second, nonmitochondrial citrate synthase. Like the mitochondrial enzyme, this enzyme was sensitive to glucose repression. It did not react with antibodies against mitochondrial citrate synthase. Haploid cells lacking a gene for mitochondrial citrate synthase grew somewhat slower than wild-type yeast cells, but exhibited no auxotrophic growth requirements.