Identification of essential residues in lysozyme: a pulse radiolysis method.

THE technique of pulse radiolysis has recently been applied to the study of the radiation inactivation of the enzyme lysozyme1. While pursuing this technique we devised the following method of identifying some of the amino-acid residues associated with the enzymatic activity of lysozyme. The results show that specific free-radical attack at a tryptophan residue destroys the enzymatic activity and is consistent with crystallographic evidence2 for the crucial role of tryptophan at the active site.