Studies of glycosidases in fresh and stored human platelets

The release by thrombin of 5 glycosidases (β-galactosidase, α-mannosidase, N-acetyl-β-glucosaminidase, β-glucuronidase, and N-acetyl-β-galactosaminidase) from human platelets was measured. Release was diminished after storage of platelets at 22 °C. and, to a lesser extent, after storage at 4 °C. Glucose stimulated the release of glycosidases by thrombin from both fresh and stored cells; acetate and pyruvate had no effect. Except for α-mannosidase, which decreased markedly, levels of glycosidases remained constant in platelets stored for 3 days at 22 °C. but rose in the plasma in which the platelets were stored. ADP and ATP inhibited β-galactosidase activity; and ATP, CTP, and GTP inhibited β-glucuronidase activity; inhibition in each case was noncompetitive. Prostaglandin-E₁, ATP, CTP, and GTP inhibited the release by thrombin of all glycosidases except α-mannosidase.