Identification of the catalytic histidine residue participating in the charge-relay system of carboxypeptidase Y

✍ Scribed by Giman Jung; Hiroshi Ueno; Rikimaru Hayashi; Ta-Hsiu Liao

• Publisher: Cold Spring Harbor Laboratory Press
• Year: 1995
• Tongue: English
• Weight: 262 KB
• Volume: 4
• Category: Article
• ISSN: 0961-8368
• DOI: 10.1002/pro.5560041123

✦ Synopsis

Abstract

The essential histidine residue of carboxypeptidase Y (CPY) was modified by a site‐specific reagent, a chloromethyl‐ketone derivative of benzyloxycarbonyl‐L‐phenylalanine. The single modified histidine residue was converted to __N__τ ‐carboxymethyl histidine (cmHis) upon performic acid oxidation. A peptide containing cmHis was isolated from the tryptic‐thermolytic digest. Based on the amino acid composition and sequence analysis, the peptide is shown to be Val‐Phe‐Asp‐Gly‐Gly‐cmHis‐MetO~2~‐Val‐Pro, which was derived from CPY cleaved by trypsin at Arg 391 and thermolysin at Phe 401, and thus His 397 was modified. This histidine residue has been implicated previously by X‐ray analysis to participate in the charge‐relay system of CPY.