Studies on Glycoproteins

Abstract

Abstract Human peripheral blood lymphocytes in culture, carefully freed of contaminating platelets, incorporated glucosamine-1-14C at a low and constant rate. Following the addition of phytohemagglutinin, there was a doubling of the rate of incorporation within 3 hours, followed by a 10- to 20-fold stimulation by the 4th day of culture and a subsequent slow decrease to twice the control rate within 14 days. The glucosamine in the acid-soluble pool appeared mainly (84%) in UDP-N-acetylglucosamine. Incorporation, which was mainly into the membrane fractions separated by differential or isopycnic density gradient centrifugation, was inhibited by puromycin. Incorporated glucosamine was preferentially released from the intact lymphocyte by proteolytic digestion, and three different classes of glycopeptides were released by papain digestion of a purified membrane fraction.