[Localization of cysteine residues in the alpha-chain of histidine decarboxylase from Micrococcus sp. n].

It was shown that the alpha-chain of histidine decarboxylase of Micrococcus sp. n. is split off by 2-nitro-5-thiocyanobenzoic acid at only one of the two cysteine residues. Determination of the C-terminal sequences, amino acid composition, molecular weight of the fragments obtained demonstrated that these fragments constitute a complete alpha-chain whose cleavage occurs at the cysteine residue which is readily modified by SH-reagents. the Ile-Cys peptide bond appeared to be resistant to cleavage under these conditions. This cleavage permitted to identify the amino acid environment of the cysteine residue active center and its localization in the alpha-chain of histidine decarboxylase.