Transamidinase of Hog Kidney

It is proposed that the transfer of the amidine group from arginine to glycine, catalyzed by transamidinase, occurs through the formation of an S-enzyme isothiourea intermediate formed by reaction between the amidine group of the substrate and a sulfhydryl group of a cysteine residue of the enzyme. The identification of the cysteine residue (isolated as cysteic acid), which appears to be involved in the binding of the amidine group, has been performed with the following procedure. Acid hydrolysis of the enzyme-amidine complex. This results in the release of 2-amino thiazoline 4-carboxylic acid carrying the carbon atom of the amidine group in position 2. Bromine oxidation of 2-amino thiazoline 4-carboxylic acid to carbamylcysteic acid. Alkaline hydrolysis of carbamylcysteic acid to cysteic acid with loss of the carbon atom originally belonging to the amidine group of the substrate.