PAF ACETYLHYDROSE & CONTROL OF PEROXIDATIVE DAMAGE TO SPERM MEMBRANES

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We study enzyme-assisted synthesis of ofigo- and poly-N-acetyflactosan-fino-glycans (NALG), a group of adhesion-mediating saccharides that also possess signalling functions. NALC-rs occur in covalent linkage with proteins and lipids, notably on mammalian cell surfaces, and also in extraceUular matrix where some of them are known as keratan sulphates. Their adhesive functions involve participation in cell-to-cell and cell-to-matrix association mediated by saccharide-protein and possibly also by saccharide-saccharide interactions. We aim to synthesize ofigo- or polysaccharides of theNALG-type, capable of binding to adhesion-mediating mammalian cell surface lectins. Being able to inhibit ce!I-to-cell. and cell-to-matrix adhesion, such saccharides may become useful as anti-- Marnmatory, anti-infective or contraceptive agents. They may also be valuable as research tools in advancing developmental biology. Large, ofigovalent ofigosaccharides should also elicit secondary responses by clustering the appropriate counter proteins on cell surfaces. Hence, saccharide-based constructs capable of inducing the irreversible acrosome reaction of sperm, should become available in thefi~iture. Our emphasis is put on construction of many relatively large and complex oligosaccharides, buton a rather modest scale. To advance structural carbohydrate analysis carried out by chemical and enzymatic degradations and by NMR and MS techniques, site-specific labeling of the constructs is actively studied. The stepwise NALG syntheses carried out in our laboratory by the Leloir pathway in vitro yield complete saccharides of N-linked, O-linked or cerwTfide-finked type, depending on the primer used. Structural characterization of the synthesis products and the intermediates is perfon-ned by degradative approaches and by NMR-spectroscopy at 500 MTIz in our own Institute. Recently, MALDI-M[S has also been applied extensively in our experiments on collaborative basis; it gives molecular masses with an admirable precision and sensitivity; MALDI-PSD and ESI-CID are used for detailed structural characterization.