STUDIES OF THREE TYPES OF GLYCOSYLTRANSFERASES

我们的主要目标之一是继续我们的研究

One of our main objectives is to continue our studies on the identification and characterization of new types of glycosyltransferases responsible for biosynthetic pathways which are different or contrary to the presently accepted pathways. For example, alpha(2,3)-sialyltransferase which will act upon galactose in L-ex or even 6'-sulfo Le-x moieties attracts our special attention. The identification of alpha-L- fucosyltransferase capable of converting the Le-x moiety to Le-y remains an objective. Various tumor cell lines and both normal and cancerous human tissues are our proposed source materials. We plan to attempt the purification of new enzyme activities. We will also purify and characterize the beta(1,3)-galactosyltransferase capable of generating the Gal-beta1->3GlcNAc sequence. Specificity of this enzyme will be studied in detail with a library of carbohydrate structures. Affinity chromatography will be employed as a key step in our purification procedures. Several types of alpha-L-fucosyltransferses and sialyltransferases can exist, and we propose to continue studies on the specificity and characterization of such enzymes, e.g. the specificity of FT-VII will be studied in detail. Glycoconjugates containing sialic acid, sulfate and fucose have attracted special attention due to their recent significance as potential ligands for selectins, the cell adhesion proteins. We plan to further elucidate the biosynthetic pathways involved in the assembly of such glycoconjugates, especially O-linked glycoproteins containing sulfate, sialic acid and fucose, e.g. GLYCAM-I, the ligand for L-selectin. The continuation of this program will allow us to fill in the various gaps that still exist in our knowledge of the specificity of these enzymes. This program has been the primary source of support for our continuing efforts at the synthesis of various acceptors, modified carbohydrate acceptor analogs, and ligands required for enzyme purification. Our modified analogs will be further examined for their potential use as enzyme inhibitors. Interest in the synthesis of modified acceptor analogs containing hydrophobic group is further enhanced as these compounds are valuable tools for the study of glycosylation processing in vivo and in vitro. Collaborative arrangements have been made for such studies in vivo. Similarly, a successful program outcome will open various avenues toward other important long term objectives. For example, the discovery and documentation of glycosyltransferases of novel specificities can enable the development of unique enzymatic and immunological probes to detect these enzymes.