Sialic Acid of Human Blood Platelets*

Abstract

The sialic acid of platelets from human group O, Rh positive blood was shown by paper chromatography to consist entirely of N-acetylneura-minic acid. Mild acid hydrolysis of platelets revealed 15.5 [mu]g sialic acid per mg of platelet protein. Free sialic acid comprised 8 to 14% of the total in frozen-thawed material. The supernatant fluid of dis-rupted platelets contained 1.6 ug free and 4.1 [mu]g total sialic acid per mg of protein. Purified neuraminidase of Vibrio cholerae released 9.5 and 11.4 [mu]g per mg protein from intact and disrupted platelets, respectively. Release of sialic acid by influenza virus was slower but essentially identical on prolonged incubation. Prior exposure of platelets to dextran decreased by 21% the amount of sialic acid re-leased by virus or bacterial enzyme. The electrophoretic mobility of platelets was reduced from -1.14 to 0.66 [mu]/second/volt/cm by neuraminidase treatment.