Azo- and Nitro-reductases of the Cestode Moniezia expansa.. Localization of the Enzyme Activities and Optimum Assay Conditions

Abstract

1. Reduction of 4-nitrobenzoic acid and 1,2-dimethyl-4-(4-carboxyphenyl-azo)-5-hydroxybenzene by the cestode Moniezia expansa occurred in the distal cytoplasm (tegumental cytoplasm) of the proglottids. No drug reduction was found in other parts of the proglottid, and no adsorbed host-derived enzymes were detected.

2. Azo- and nitro-reductase activities were found in the 75 000 g supernatant. No activity was observed in the 75 000 g pellet.

3. Both enzyme activities required as cofactors NADH₂ and either glutathione or cysteine; NADPH₂ gave about half the activity of NADH₂.

4. The optimal pH of both reductases was about 6-5, and neither activity was inhibited by CO, O², EDTA or sodium azide.

5. Ammonium sulphate fractionation procedures failed to separate azo- and nitro-reductase activities.

6. The molecular weight of both azo- and nitro-reductase enzymes was about 125 000.