Aerobically grown bakers’ yeast has been shown to contain two different lactic cytochrome c reductases, one of which is specific for L( +)-lactate (1) and the other of which is specific for D( -)-lactate (2). Neither of these two enzymes is present in anaerobically grown yeast, which contains instead a D( -)lactic dehydrogenase that does not reduce cytochrome c. No L( +)-lactic dehydrogenase is...