ENZYMATIC TRANSFER OF 14C-GLUCOSAMINE FROM UDP-N-ACETYL-14C-GLUCOSAMINE TO ENDOGENOUS ACCEPTORS IN A GOLGI APPARATUS-RICH FRACTION FROM LIVER

A Golgi apparatus-rich fraction isolated from rat liver catalyzes the transfer of glucosamine from UDP-N-acetylglucosamine to endogenous protein acceptors. The Golgi-associated transfer accounts for almost half of the total activity of the original homogenate. Plasma membrane and endoplasmic reticulum fractions are practically devoid of activity. GDP-mannose and GTP stimulate this transfer, possibly by sparing UDP-N-acetylglucosamine from enzymatic hydrolysis. UDP-glucose, UDP-galactose, UTP, UDP, and UMP are inhibitory. Digestion with pronase converts the radioactive product of this transfer into a trichloroacetic acid-soluble form. All of the radioactive material cochromatographs with glucosamine, following acid hydrolysis of pronase glycopeptides. © 1969.