CDNA CLONING AND SEQUENCING OF MOUSE MASTOCYTOMA GLUCOSAMINYL N-DEACETYLASE N-SULFOTRANSFERASE, AN ENZYME INVOLVED IN THE BIOSYNTHESIS OF HEPARIN/

A 110-kDa protein involved in heparin biosynthesis in mouse mastocytom a cells was previously shown to express both glucosaminyl N-deacetylas e and N-sulfotransferase activity. In this study, the complete nucleot ide sequence corresponding to this protein is reported. The mRNA, esti mated to contain 3.9 kilobases encodes a protein with an M(r) of 101,0 92. The predicted domain structure of the protein resembles those of p reviously characterized Golgi proteins with an N-terminal cytoplasmic tail, a single membrane-spanning domain, and a large catalytic domain linked to the transmembrane domain through a ''stem region.'' Comparis on of the deduced amino acid sequence of the mouse mastocytoma protein and a previously cloned similar enzyme from rat liver demonstrated th at while large portions of the proteins, corresponding essentially to the putative catalytic domains, were closely related, other portions, in particular in the N-terminal parts, were markedly different. The di vergence was not due to species differences since two separate mouse t ranscripts could be identified that hybridized with probes specific fo r the two proteins. Also, functional differences were noted since the mastocytoma enzyme, contrary to the liver enzyme, requires a polycatio n cofactor for expression of N-deacetylase activity. The results are d iscussed in relation to the structural properties of heparin and hepar an sulfate.