Reduction of ribonuclease by glutathione at elevated temperatures: the molecular mechanism.

1. The mechanism of the reaction between ribonuclease and GSH at elevated temperatures has been studied by using N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide to label the reduced ribonuclease. 2. After incubation for 2hr. at 35 degrees , enzymically active ribonuclease was recovered; at 50.8 degrees half of the initial ribonuclease was recovered as enzymically active ribonuclease and half as reduced labelled ribonuclease; at 55 degrees all of the initial ribonuclease was recovered in the labelled form. 3. It was inferred that the rate-limiting step was the reduction of the first disulphide bond in any one molecule. This was followed by rapid reduction of the other bonds in the same molecule.