Alcohol: NAD Oxidoreductase (E. C. 1.1.1.1.) from Peas

Abstract

SUMMARY– The substrate specificity of the enzyme alcohol: NAD oxidoreductase from seeds and pods of the pea plant ( Pisum sutivum ) was investigated. The enzyme catalyzes the oxidation of primary aliphatic alcohols especially 2‐alken‐1‐01s e.g. , trans‐2‐hexen‐1‐01, under the conditions used. It also catalyzes the reduction of aliphatic aldehydes especially ethanal, hexanal and unsaturated nonanals. The reaction product was routinely identified by mass spectrometry. The enzyme activity was found to be inhibited competitively by fatty acids, methanol, imidazol and L‐histidine. The enzyme was used as a catalyst in experiments for determining equilibrium constants and the calculation of the free energy change of some alcohol‐aldehyde systems in the presence of oxidized and reduced coenzyme. On the basis of the equilibrium constants determined, the composition of various alcohol‐aldehyde mixtures were calculated for different NAD + 2 NADH ratios and different pH values. The enzyme preparation could not be separated into fractions with altered substrate specificity by ammonium sulfate precipitation or by ion exchange chromatography.