title: Carboxypeptidase A activity of cultured skin fibroblasts and relationship to cystic fibrosis.
abstract: Properties of carboxypeptidase A of cultured skin fibroblasts from control and cystic fibrosis patients were studied using alpha-N-carbobenzoxy-L-glutamyl-L-tyrosine as substrate. Carboxypeptidase A was inhibited by thiomersal, cyanide, iodoacetate and N-ethylmaleimide in a similar manner for control and cystic fibrosis fibroblasts. Both trypsin and dithiothreitol treatment activated the enzyme, but 1,10-phenanthroline inhibited only in the presence of dithiothreitol. Both Zn2+ and Co2+ reversed this inhibition. Trypsin treatment of carboxypeptidase A produced a form of the enzyme having a higher KM value for both control and cystic fibrosis fibroblasts. Dithiothreitol treatment of control fibroblasts resulted in a form with similar properties to the trypsin activated form, but cystic fibrosis fibroblasts yielded a variant form with even higher KM and Vmax values. Since other properties were similar, it seems likely that this difference reflected binding of a molecule to the enzyme rather than of a defect in the enzyme.
mesh_terms: D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D003550:Cystic Fibrosis / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology; D012867:Skin / Q000201:enzymology*
chemical_list: D002268:Carboxypeptidases