Characterisation of a carboxypeptidase in human serum distinct from carboxypeptidase N.
Arginine carboxypeptidase activity in human serum, measured with the hippuryl-L-arginine substrate, is about three times higher than in human plasma. This difference is much smaller when hippuryl-L-lysine is used as the substrate. When fresh serum is incubated at 30 degrees C, the arginine and lysine carboxypeptidase activity decreases until a stable activity, close to the plasma activity, is reached. This stable carboxypeptidase activity is attributed to carboxypeptidase N. The unstable carboxypeptidase differs from carboxypeptidase N in pH-optimum, esterase activity, substrate specificity, Co2+-activation and dithiotreitol activation. Blood cells are not responsible for the release of this enzyme during coagulation. No activator of carboxypeptidase N was detectable in human serum. Ion-exchange chromatography on DEAE-cellulose confirms the presence of two different molecular forms of arginine carboxypeptidase activity.
Department of Medical Biochemistry, Faculty of Medicine, University of Antwerp, Wilrijk, Belgium.
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Hendriks
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Scharpé
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van Sande
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Lommaert
D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001780:Blood Coagulation Tests; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors / Q000097:blood*; D055598:Chemical Phenomena; D002621:Chemistry; D002848:Chromatography, DEAE-Cellulose; D003035:Cobalt / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability; D004950:Esterases / Q000097:blood; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D001121:Lysine Carboxypeptidase / Q000037:antagonists & inhibitors / Q000097:blood*; D008297:Male; D010949:Plasma / Q000032:analysis; D013379:Substrate Specificity; D013696:Temperature
D003035:Cobalt; C029729:2-mercaptomethyl-3-guanidinoethylthiopropionic acid; D006493:Heparin; D015097:3-Mercaptopropionic Acid; D004950:Esterases; D002268:Carboxypeptidases; D001121:Lysine Carboxypeptidase; C018021:cobaltous chloride; D004229:Dithiothreitol