As various isoenzymes of gastric alcohol dehydrogenase exist and as the effect of sex and age on these enzymes is unknown, this study measured the activity of gastric alcohol dehydrogenase at high and low ethanol concentrations in endoscopic biopsy specimens from a total of 290 patients of various ages and from 10 patients with chronic alcoholism. Gastric alcohol dehydrogenase was also detected by immunohistological tests in biopsy specimens from 40 patients by the use of a polyclonal rabbit antibody against class I alcohol dehydrogenase. A significant correlation was found between the immunohistological reaction assessed by the intensity of the colour reaction in the biopsy specimen and the activity of alcohol dehydrogenase measured at 580 mM ethanol. While alcohol dehydrogenase activity measured at 16 mM ethanol was not significandy affected by age and sex, both factors influenced alcohol dehydrogenase activity measured at 580 mM ethanol. Young women below 50 years of age had significantly lower alcohol dehydrogenase activities in the gastric corpus and antrum when compared with age matched controls (SEM) (6.4 (0.7) v 8-8 (0.6) nmol/min/mg protein; p<0-001 and 6-0 (1-3) v 9.5 (1.3) nmol/min/mg protein; p<0001). Over 50 years ofage this sex difference was no longer detectable, as high Km gastric alcohol dehydrogenase activity decreases with age only in men and not in women. In addition, extremely low alcohol dehydrogenase activities have been found in gastric biopsy specimens from young male alcoholics (2-2 (0.5) nmol/min/mg protein), which returned to normal after two to three weeks of abstinence.The activity of alcohol dehydrogenase in the human stomach measured at 580 mM ethanol is decreased in young women, in elderly men, and in the subject with alcoholism. This decrease in alcohol dehydrogenase activity may contribute to the reduced first pass metabolism ofethanol associated with raised ethanol blood concentrations seen in these people. (Gut 1993; 34: 1433-1437 Recent studies in men '-3and

An atypical alcohol dehydrogenase was found in two human livers. The anomalous enzyme, which has been purified, differs from the normal regarding (a) pH rate profile, (b) substrate specificity, and (c) sensitivity to metal binding agents. Thiourea inhibits the variant enzyme, but activates normal human liver alcohol dehydrogenase. A simple screening test is described to differentiate between atypical and normal alcohol dehydrogenase in liver homogenate. Total alcohol dehydrogenase activity was considerably higher in livers containing the atypical enzyme.

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Initial-rate analysis of the carbonyl reductase-catalysed reduction of menadione by NADPH gave families of straight lines in double-reciprocal plots consistent with a sequential mechanism being obeyed. The fluorescence of NADPH was increased up to 7-fold with a concomitant shift of the emission maximum towards lower wavelength in the presence of carbonyl reductase, and both NADPH and NADP+ caused quenching of the enzyme fluorescence, indicating formation of a binary enzyme-coenzyme complex. Deuterium isotope effects on the apparent V/Km values decreased with increasing concentrations of menadione but were independent of the NADPH concentration. The results, together with data from product inhibition studies, are consistent with carbonyl reductase obeying a compulsory-order mechanism, NADPH binding first and NADP+ leaving last. No significant differences in the kinetic properties of three molecular forms of carbonyl reductase were detectable.