Endogenous calcium-activated neutral protease in human platelets. Identification of a Mr 70,000 substrate.
Endogenous calcium-activated neutral protease (CAP, calpain), the major proteolytic activity in human platelets, cleaves a number of proteins. Preferential substrates are actin-binding protein, P 235, and a Mr 83,000 component. A fourth substrate completely degraded by CAP in platelet lysate within seconds is a Mr 70,000 protein. This polypeptide has been shown to influence the electrophoretic behaviour of membrane glycoprotein Ib during isoelectric focusing probably by forming a complex. This in vitro effect suggests that cleavage of the Mr 70,000 protein by CAP might modulate glycoprotein Ib receptor function. Proteolysis of known substrates by CAP during thrombin-induced platelet aggregation could not be detected.
Meyer
M
M
Medical Academy Erfurt, Department of Medical Genetics, GDR.
D001792:Blood Platelets / Q000201:enzymology*; D002154:Calpain / Q000302:isolation & purification*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D037102:Lectins; D010455:Peptides / Q000302:isolation & purification; D013379:Substrate Specificity
D037102:Lectins; D010455:Peptides; D002154:Calpain