Studies on the pH-5 enzyme I. The effects of ribonuclease and some SH inhibitors on the amino hydroxamate formation by the pH-5 enzyme of rabbit liver

Abstract

The pH-5 enzyme was isolated from rabbit liver by the modified method of Hoagland et al. and the effects of some SH inhibitors, azide, and RNase on the amino hydroxamate formation by this enzyme were investigated. The following results were obtained: 1. 1. p-Chloromercuribenzoate, monoiodacetate and azide failed to inhibit the amino acid-dependent hydroxamate formation by the pH-5 enzyme. 2. 2. When the pH-5 enzyme, pretreated with RNase, was incubated with ATP and the amino acid mixture, the amount of hydroxamate formed by the amino acid decreased, as compared with the control experiment in which the pH-5 enzyme had not been pretreated with RNase. From these results it is concluded that the SH group is not involved in most of the amino hydroxamate formation by the pH-5 enzyme, and that, by contrast, the RNA of the enzyme plays an essential part in this reaction. The possible mechanism by which this RNA participates in the amino hydroxamate formation is discussed.