FORMATION OF N-PROPYL ALCOHOL BY CELL-FREE EXTRACTS OF SACCHAROMYCES CEREVISIAE*

Abstract

n-Propyl alcohol formation from α-ketobutyric acid was obtained in cell-free extracts of Saccharomyces cerevisiae var. ellipsoideus and the optimal conditions for the formation were determined. In the presence of NAD† the concentration of n-propyl alcohol formed was the same with extracts of yeast grown either aerobically or anaerobically, but in the presence of NADP more n-propyl alcohol was formed with extracts of aerobic yeast. There was no evidence for an increase in an NADP-specific alcohol dehydrogenase, and the increased formation of n-propyl alcohol by extracts of aerobic yeast with added NADP was attributed to a greater reductive capacity of the extracts of aerobic cells in the presence of NADP. No system of enzymes for the formation of n-propyl alcohol was found other than those involved in ethyl alcohol formation. However, alcohol dehydrogenase from aerobic cells had a greater specificity for n-propyl alcohol, compared with ethyl alcohol, than the enzyme from anaerobically grown cells. This difference may be part of the explanation for greater n-propyl alcohol formation in aerobic cultures.