Incorporation of carbohydrate into protein of human platelets

Human platelets incorporated glucosamine and mannose into protein. Incorporation in whole or disrupted cells was reduced considerably by incubation with thrombin. The effect of thrombin appeared to be due to hydrolysis of glycoprotein. Cyanide and fluoride also markedly inhibited incorporation; concanavalin A, prostaglandin E₁, aspirin, ADP, and puromycin had no effect. Neither concanavalin A, ADP or prostaglandin E₁ blocked the inhibition of incorporation by thrombin. The experiments indicate that human platelets add carbohydrate onto pre-existing protein by an energy-dependent process and that this glycoprotein is hydrolyzed by thrombin.