Absence of 5-Hydroxy-4-Ketohexanoate and the alpha-Ketoglutarate Dehydrogenase Complex in Mutants of Saccharomyces oviformis Incapable of Growing on Ethanol.

The roles of the enzyme which forms 5-hydroxy-4-ketohexanoate (HKH) and of related enzymes in the metabolism of ethanol were studied in Saccharomyces oviformis WH92 and its mutants, which grew poorly or not at all on ethanol. The strains, which did not grow on ethanol, did not form HKH from alpha-ketoglutarate and acetaldehyde enzymatically and were also devoid of the alpha-ketoglutarate dehydrogenase complex. Acetaldehyde inhibited the activity of alpha-ketoglutarate dehydrogenase. These mutants did not grow on acetate since they had no acetyl-CoA synthetase activity. The relationship of the formation of HKH with the metabolism of ethanol is discussed.