Glycosyltransferases
Goal: An improved understanding of the mechanism and specificity of glycosyltransferases,
including protein N-glycosylation catalyzed by oligosaccharyltransferase.
Glycosyltransferases catalyze the reaction of numerous glycosyl donors and a
wide variety of carbohydrate or protein acceptors. Research in our group involves glycosylation of N-acetylglucosamine
(GlcNAc) derivatives such as a sugar nucleotide (e.g., UDP-GlcNAc) or a
lipid-linked saccharide (e.g., GlcNAc-b-(1,3)-GlcNAc-a-PP-dolichol) to a carbohydrate (e.g.,
lactose) or peptide (e.g., Bz-Asn-Leu-Thr-NH2), respectively. In addition, other reactions that utilize
sugar nucleotides (i.e., C-4 epimerases, C-2 epimerases, 5,6-dehydratase/reductase)
are also under investigations in collaborative research. Using synthetic probes of catalytic
mechanism, this diverse group of enzymes is the subject of ongoing study.
Another group of glycosyltransferases are part of the so-called “dolichol
pathway” involved in the biosynthesis of the complex triantennary
oligosaccharide donor required in the formation of N-linked glycoproteins. To elucidate the catalytic mechanism of several
enzymes in this pathway, we have synthesized several new carbohydrates,
including sugar nucleotides and lipid-linked saccharides. The final enzyme in this pathway is oligosaccharyltransferase
(OST). OST is a membrane-bound,
heterooligomeric protein that we isolate from yeast. Initial research in our
group centered on the use of synthetically accessible small substrates,
characterization of the chemical structure of the glycopeptide product, and the
use of isotopically labeled (1H, 13C, 15N)
peptide acceptor substrates for mechanistic studies. More recent research focused
on the use of larger peptides and proteins as substrates and has led to
extensive studies with invertase-derived peptides of varying length. Kinetic
data combined with structure-activity data has allowed us to develop a working
hypothesis concerning peptide substrate recognition by OST. Current research involves
the synthesis of a variety of isotopically labeled donor substrates and
inhibitors designed to answer specific mechanistic questions. As in the
research with the folate polyglutamates and trypanothione, the goal here is to
understand the mechanism of this reaction in sufficient detail that it will be
feasible to design and synthesize potent and specific inhibitors for use in the
study of cellular glycoprotein biosynthesis.
Links related to Glycosyltransferases and OST
Researchers interested in Glycosyltransferases
and OST
Marcus Aebi at ETH.
Reid Gilmore at the
University of Massachusetts.
Barbara Imperiali at MIT.
Andrea
Vasella at ETHZ.
If you are a researcher interested in glycosyltransferases, including OST
please drop us a note and we will add
you to our list!
|