Role of metal ions in goat carboxypeptidase A-catalysed hydrolysis of acyl peptides. 1984

R D Dua, and K K Gupta

The carboxypeptidase A purified from goat pancreas has been found to have a molecular weight of 34,600 +/- 300. The enzyme is a zinc-protein and the molar ratio of zinc to enzyme protein is 1:1. Removal of zinc yields an inactive apocarboxypeptidase A. The loss of activity of the native enzyme and restoration of the activity of the apoenzyme run parallel with the zinc content of the protein, thus showing the essentiality of zinc for the enzymatic activity. The exact role of zinc in the enzyme catalysed hydrolysis of the acylpeptides has been investigated after preparing metallo proteins by substituting the zinc of carboxypeptidase A with Co2+, Mn2+, Ni2+, Fe2+, Cd2+, Hg2+, and Cu2+ and determining the kinetic parameters of such metalloproteins. These studies indicate that the metal ion is involved in both binding the substrate and polarising the peptide bond.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008670 Metals Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th ed) Metal
D010179 Pancreas A nodular organ in the ABDOMEN that contains a mixture of ENDOCRINE GLANDS and EXOCRINE GLANDS. The small endocrine portion consists of the ISLETS OF LANGERHANS secreting a number of hormones into the blood stream. The large exocrine portion (EXOCRINE PANCREAS) is a compound acinar gland that secretes several digestive enzymes into the pancreatic ductal system that empties into the DUODENUM.
D010455 Peptides Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are considered to be larger versions of peptides that can form into complex structures such as ENZYMES and RECEPTORS. Peptide,Polypeptide,Polypeptides
D002268 Carboxypeptidases Enzymes that act at a free C-terminus of a polypeptide to liberate a single amino acid residue. Carboxypeptidase
D002413 Cations, Divalent Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis. Divalent Cations
D004151 Dipeptides Peptides composed of two amino acid units. Dipeptide
D004950 Esterases Any member of the class of enzymes that catalyze the cleavage of an ester bond and result in the addition of water to the resulting molecules. Esterase
D006041 Goats Any of numerous agile, hollow-horned RUMINANTS of the genus Capra, in the family Bovidae, closely related to the SHEEP. Capra,Capras,Goat
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations

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