Azo- and Nitro-Reductases of the Cestode Moniezia expansa. Substrate specificity, reaction products and the effects of flavins and other compounds

Abstract

1. The effects of various inhibitors and activators on the azo- and nitro-reductases of Momenta expansa have been studied. Both reductions were partially inhibited by FAD, FMN, riboflavin, allopurinol, dicoumarol, 5-nitro-2-fural-dehyde, azide and cyanide at 1 mM. Both reactions were stimulated by hypoxanthine. Menadione, nitrofurantoin, SKF 525-A (2-diethylaminoethyl 2,2-diphenylvalerate) and fluoride were without effect.

2. Xanthine- and aldehyde-oxidase activities were not detected in the enzyme preparation.

3. The substrate specificity of the azo- and nitro-reductases were determined. Azobenzene, 4-dimethylamino-azobenzene and l,2-dimethyl-4-(4-carboxyphenylazo)-5-hydroxybenzene, nitrobenzene, 4-nitrohippuric acid and the isomers of nitrophenol, nitroanisole, nitrobenzoic acid, nitrobenzalde-hyde and nitrobenzyl alcohol were reduced. Nitrobenzaldehyde isomers were not reduced to the alcohols and the coumaric acids were not reduced to the phenylpropionic acids.

4. The products of azo- and nitro-reduction were the corresponding amines; hydroxylamino- and hydrazo-compounds were not detected.

5. The pH optima and cofactor requirements were the same for both azo-and nitro-reduction. Neither reaction was inhibited by oxygen.