title: Direct chemical evidence for the mixed anhydride intermediate of carboxypeptidase A in ester and peptide hydrolysis.
abstract: Carboxypeptidase A was incubated at -60 degrees C with an excess of O-(trans-p-chlorocinnamoyl)-L-phenyllactate, O-(hippuryl)-glycolate or N-(hippuryl)-L-phenylalanine. After rapid denaturation with trichloracetic acid the precipitated protein was reduced with [3H]NaCNBH3. 3H Labeled enzyme was isolated by gel chromatography on Sephadex G-25. After complete acid hydrolysis the specific label within the protein was identified by high voltage paper electrophoresis and paper chromatography as [3H]2-amino-5-hydroxyvaleric acid, the reduction product of a gamma-acylated glutamic acid. These results give strong evidence that a mixed anhydride intermediate is formed, which for the first time was identified during the hydrolysis of classical ester as well as peptide substrates by direct chemical means.
mesh_terms: D002268:Carboxypeptidases / Q000378:metabolism*; D043422:Carboxypeptidases A; D002854:Chromatography, Paper; D004590:Electrophoresis, Paper; D006016:Glycolates / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D007773:Lactates / Q000378:metabolism; D008956:Models, Chemical; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D006016:Glycolates; D007773:Lactates; D010649:Phenylalanine; C049124:O-(hippuryl)glycolate; C049123:N-(hippuryl)phenylalanine; C049125:O-(4-chlorocinnamoyl)phenyllactate; D002268:Carboxypeptidases; D043422:Carboxypeptidases A