A thioamide substrate of carboxypeptidase A.
Carbobenzoxythioglycyl-L-phenylalanine [CbzNHCH2C(==S)Phe, Z-Glys-Phe] was synthesized as thioamide analogue of Z-Gly-Phe, a known substrate of carboxypeptidase A (CPA). By use of a ninhydrin-based assay and Z-Gly-Gly-Phe as the substrate, Z-Glys-Phe was shown to be a weak competitive inhibitor of CPA (Ki = 1.4 mM). The L isomer (but not the D) of Z-Glys-Phe proved to be a substrate for CPA (Km = 1.1 mM and kcat = 5.3 s-1 at pH 7.5), binding with comparable affinity to, but hydrolyzing at 10% the rate of, the oxo analogue Z-Gly-Phe. The CPA-catalyzed hydrolysis of Z-Glys-Phe was shown to involve only C-N bond cleavage, to give carbobenzoxythioglycine and phenylalanine.
D000577:Amides / Q000378:metabolism*; D001667:Binding, Competitive; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043422:Carboxypeptidases A; D004151:Dipeptides / Q000378:metabolism*; D007700:Kinetics; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity; D013854:Thioamides / Q000378:metabolism* / Q000494:pharmacology
D000577:Amides; D004151:Dipeptides; D013854:Thioamides; C019156:carbobenzoxyglycylphenylalanine; D002268:Carboxypeptidases; D043422:Carboxypeptidases A