[Partial characteristics of the basic phenylmethylsulfonylfluoride-inhibited carboxypeptidase from cat brain].

Cat brain carboxypeptidase releasing C-terminal arginine from the synthetic substrate, dansyl-Phe-Leu-Arg, was partially characterized. The enzyme has a molecular weight of 100-120 kDa, displays the maximal activity at pH 6.0-6.5 and is strongly inhibited by phenylmethanesulfonylfluoride and 4-chloromercuribenzoate, less strongly (by 40%) by iodoacetamide and is not inhibited by N-ethylmaleimide, 2-mercaptoethanol, EDTA, Co2+ and guanidinoethylmercaptosuccinic acid. The Km values for the hydrolysis of dansyl-Phe-Leu-Arg and dansyl-Phe-Ala-Arg by soluble carboxypeptidase are 48 and 96 microM, respectively. By all properties, this carboxypeptidase differs from other known carboxypeptidases. Possible participation of the enzyme in neuropeptide metabolism is discussed.