The estimation of alcohol dehydrogenase activity in aerobic and anaerobic "permeabilised" baker's yeast cells.

The in vivo and in vitro activity of alcohol dehydrogenase from baker's yeast maintained under aerobic and anaerobic conditions was measured. In vivo measurements were made in cells "permeabilised" with toluene. Michaelis constants (NAD+ as substrate) were found to be almost identical as those reported for purified preparations. In addition the Km of the enzyme from cells incubated under anaerobic conditions was virtually identical to that from cells from aerobic conditions. The activity of the enzyme was found to be greater (in both "permeabilised" cells and extracts) in cells maintained under nitrogen than air. Cells metabolizing glucose in N2 produced greater levels of ethanol than in air and the rate of NAD+ reduction was also found to be greater in N2 than in air. The results indicate that it was feasible to determine rates of this enzyme in vivo and that the difference in activity of alcohol dehydrogenase under N2 and air may conceivably account for differences in rates of glucose utilisation, ethanol production and NAD+ reduction in air and nitrogen.