N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H2O2/Cl− System

Abstract

The chlorination of dipeptides by the myeloperoxidase/H2O2/Cl− system takes place at the N‐terminal amino group, whereas no chlorination of the amide nitrogen of the peptide bond can be observed. The N‐terminal amino group is chlorinated to N‐monochloroamine or/and N‐dichloroamine. N‐Monochloropeptides were the main products at higher pH values, at lower pH a mixture of N‐monochloropeptides andN‐dichloropeptides was formed owing to the dismutation of N‐monochloroamine to N‐dichloroamine. N‐Monochloropeptides decompose, yielding NH3 and the corresponding N‐(2‐oxoacyl)amino acids. N‐Dichlorodipeptides decompose faster but to nitriles and the free C‐terminal amino acids. N‐Dichloroglycyl‐amino acid decomposes through a relatively stable intermediate (cyano‐formylamino acid) to hydrogen cyanide, cyanogen chloride and the free C‐terminal amino acid. Insulin chlorination also yields N‐terminal glycyl and phenylalanyl N‐monochloro derivatives, which deaminate to glyoxylyl and phenylpyruvyl residues. Copyright © 1978, Wiley Blackwell. All rights reserved