Kinetic Equivalence of the Active Sites of Alcohol Dehydrogenase from Horse Liver

Abstract

The reduction, catalysed by liver alcohol dehydrogenase, of benzaldehyde in the presence and absence of pyrazole, and the oxidation of benzyl alcohol and cyclohexanol in the presence of isobutyramide, has been measured by the stopped-flow technique. In performing these experiments particular care was taken to purify the enzyme, coenzymes, substrates and inhibitors, and to minimise as much as possible the effects of a blank substrate reaction. The calculation of the amount of substrate converted to product during the various phases of the transient process was based on the absorption coefficients for the enzyme-coenzyme and enzyme-coenzyme-inhibitor complexes determined in the absence of substrate. The results show that the two active sites of liver alcohol dehydrogenase are kinetically equivalent and that the enzyme does not exhibit half-of-the-sites reactivity.