Chymopapain. II. Photooxidation of histidine residues.

31 December 1975

journal article
research article
Published by Pharmaceutical Society of Japan in CHEMICAL & PHARMACEUTICAL BULLETIN

Vol. 24 (12) , 3088-3092
https://doi.org/10.1248/cpb.24.3088

Abstract

The rate of photo-inactivation of chymopapain A was pH-dependent. About 3 histidine residues were oxidized, and enzyme activity was lost during the disappearance of the 1st oxidizable histidine residue. The essential SH group was not affected by photooxidation. About 2 tryptophan residues were oxidized at pH 8.0 with loss of activity and at pH 4.0 with no loss activity. Two photooxidizable tryptophan residues were found to be different from the essential tryptophan residue by means of NBS [N-bromosuccinimide] oxidation. Apparently the modification of single histidine residue is the cause of activity loss by the photooxidation.

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