A MONOMERIC PROTEIN IN THE GOLGI MEMBRANE CATALYZES BOTH N-DEACETYLATION AND N-SULFATION OF HEPARAN-SULFATE

Recent studies have shown that the rat liver heparan sulfate N-deacety lase/N-sulfotransferase is a glycoprotein encoded by a single polypept ide chain of 882 amino acids. Using radiation inactivation analyses, w e have now determined that in rat liver Golgi vesicles the target size for the N-deacetylase is 88 +/- 14 kDa, whereas that of the N-sulfotr ansferase is 92 +/- 8 kDa. These results, together with previous bioch emical and molecular cloning approaches, demonstrate that 1) in rat Li ver Golgi membranes there exists only one population of molecules expr essing both activities, 2) the active protein in the Golgi membrane fu nctions as a monomer, and 3) there is no evidence that a large indepen dent protein acts as a regulator of either activity.