Reduktion aromatischer Säuren zu Aldehyden und Alkoholen im zellfreien System: 2. Reinigung und Eigenschaften von Aryl‐Alkohol: NADP‐Oxidoreduktase aus Neurospora crassa

Abstract

A new alcohol dehydrogenase preferably acting on aromatic primary alcohols (resp. aldehydes) has been isolated from mycelia of the fungus Neurospora crassa. The enzyme was purified about 450‐fold by protamine treatment, ammonium sulphate fractionation, adsorption on calcium phosphate gel, and chromatography on Sephadex G‐200 and DEAE‐cellulose. Its molecular weight was tentatively estimated to be about 75,000 by use of a calibrated Sephadex G‐200 column. The enzyme needs NADPH as cofactor; with NADH, the velocity of the reaction is decreased to less than 1% of the rate achieved with NADPH. Maximum rates of reaction were observed in the case of aldehyde reduction at pH 6.8; in the reverse reaction, pH 8.8 was optimal. By raising the temperature of the incubation mixture, a linear increase of the reaction velocity up to 55° was noted. The enzyme shows a broad range of substrate specificity towards both aromatic and to a lesser extend aliphatic aldehydes (resp. alcohols). The equilibrium constant (Formula Presented.) Treatment of the enzyme with iodosobenzoate and p‐chloromercuribenzoate resulted in an inhibition, while N‐ethylmaleimide and iodoacetate had no effect. Substrate specificity studies as well as other properties indicate that this enzyme differs from any known alcohol dehydrogenase. We propose the systematic name aryl alcohol: NADP oxidoreductase (EC 1.1.1.2). Copyright © 1969, Wiley Blackwell. All rights reserved