title: Chicken liver Pz-peptidase, a thiol-dependent metallo-endopeptidase.
abstract: Pz-peptidase was purified from chicken liver as a protein of Mr 80,000 and pI 5.2. The purified enzyme hydrolysed phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-D-Arg, 2,4-dinitrophenyl-Pro-Leu-Gly-Pro-Trp-D-Lys. 7-methoxycoumarin-3-carboxylyl-Pro-Leu-Gly-Pro-D-(2,4-dinitropheny l)Lys, benzoyl-Gly-Ala-Ala-Phe-p-aminobenzoate, Ac-Ala4 (at the Ala-1-Ala-2 bond) and bradykinin (at the Phe-5-Ser-6 bond). No hydrolysis of proteins was detected. Loss of activity in the presence of EDTA or 1,10-phenanthroline was time-dependent. Metal ions found to restore activity after treatment with EDTA were Zn2+, Mn2+, Ca2+, Co2+ and Cd2+, in decreasing order of effectiveness. Ni2+, Fe2+ and higher concentrations of Zn2+ were inhibitory. Inhibition by N-[1-(RS)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-aminobenzoate and related compounds showed Ki values (down to 5 nM) somewhat lower than those for the rat enzyme. Pz-peptidase was activated by low concentrations of 2-mercaptoethanol and dithiothreitol, but inhibited by higher concentrations. p-Chloromercuribenzoate and some other thiol-blocking reagents were inhibitory. Inactivation by diethyl pyrocarbonate that was reversible by hydroxylamine showed the presence of essential histidine residue(s). We conclude that chicken Pz-peptidase is a metallo-endopeptidase with thiol-dependence. Moreover, the properties of chicken Pz-peptidase agree with those described for mammalian soluble metallo-endopeptidase and endo-oligopeptidase A. consistent with the view that these three types of activity are all attributable to the single enzyme for which the name thimet peptidase has been proposed.
authors.affiliation: Department of Biochemistry, Strangeways Research Laboratory, Cambridge, U.K.
authors.forename: A J
authors.initials: AJ
authors.lastname: Barrett
authors.forename: M A
authors.initials: MA
authors.lastname: Brown
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D010450:Endopeptidases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight
chemical_list: D004492:Edetic Acid; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D008666:Metalloendopeptidases; C022510:thimet oligopeptidase