New Assay of the Ribonuclease-reactivating Enzyme based on Disulphide Exchange

Abstract

RECENTLY, Straub and I described experiments which suggested that the ribonuclease-reactivating enzyme isolated from pig pancreas probably acts through a rearrangement of disulphide bridges of the substrate by means of disulphide–sulphydryl interchange^1,2. Further evidence in favour of this hypothesis has been reported by Givol et al.³. However, the action of this enzyme was followed in both laboratories by indirect methods, that is, by measuring the rate of appearance or disappearance of the activity of another enzyme (ribonuclease or chymotrypsin). This communication describes a convenient assay method which eliminates many uncertainties of the indirect reactivation–inactivation tests and further supports the proposed interchange mechanism.