4-Nitrobenzoic Acid Reductase of the Nematode Ascaris lumbricoides var suum. Localization of the Enzyme and Optimum Assay Conditions

Abstract

1. Reduction of 4-nitrobenzoic acid by the nematode Ascaris lumbricoides var suum occurred in the intestinal brush border cells. Cuticle, mesenchyme fluid and reproductive tissue showed no activity.

2. 4-Nitrobenzoic acid reductase was in the supernatant fraction after centrifugation of intestinal homogenates at 75000 g for 2 h.

3. The enzyme required as cofactors NADH₂, a low molecular weight thiol such as glutathione or cysteine and a divalent metal ion such as Mn⁺⁺ or Cu⁺⁺. The reduction was not catalysed by NADPH₂.

4. Reduction was not inhibited by O₂ or CO. Optimum pH of the reaction was about 6·5.