In recent years, the possibility of some glycosyltransferases acting as tumor markers has become apparent. In this program we are concentrating our efforts on the study of human fucosyl, galactosyl, and sialytransferases. We do not intend to purify each of these glycosyltransferases other than galactosyltransferase. Much emphasis will be placed on the specificity studies of these enzymes with the aid of oligosaccharides and appropriate acceptors obtained from glycoconjugates. A variety of synthetic acceptors required for the program have already become available in our laboratory. These investigations should lead to the discovery of a highly specific acceptor for a specific type of glycosyltransferase. Utilizing this specific acceptor, levels of glycosyltransferase activity in the sera of healthy individuals and in specimens obtained from ovarian cancer patients will be examined. In fact, we have already made effective use of synthetic compounds as acceptors for several enzymes. Modified assay procedures for certain enzymes in the proposed investigations have been developed in our laboratory. The glycosidic linkage from a sugar nucleotide to the acceptor formed by the catalytic reaction of a glycosyltransferase will be established by various procedures. Some specific glycosidases required for the characterization of this linkage are available in our laboratory. In this program, we do not merely propose to duplicate the studies of these three glycosyltransferase systems as reported by other investigators, but rather to attempt to resolve the existing confusion and discrepancies regarding these enzymes as tumor markers. Precisely, we are proposing to undertake a systematic approach for the biochemical studies of these three types of glycosyltransferases. Our clinical studies are limited and involve the use of specimens from only ovarian cancer patients. (1)