The goal of the proposed research is to develop a general and highly efficient chemo enzymatic method for making diverse homogeneous glycopeptides and glycoproteins of biomedical significance. A major problem in functional glycomics studies and glycoprotein therapeutic applications is the lack of efficient methods to produce glycan-defined glycoproteins. We have recently developed a chemo enzymatic method that exploits the trans glycosylation activity of a class of endoglycosidases (ENGases) that enables the "native ligation" between free glycan and GlcNAc- tagged protein to form homogeneous glycoproteins with native glycosidic linkage. We found that synthetic glycan oxazoline and ENGase-based glycosynthase that we created is an excellent pair for an efficient transglycosylation. This method permits independent manipulations of the sugar and protein portions, providing a highly convergent and potentially general approach to glycoprotein assembly. In this renewal application, we aim at expanding the scope of the chemo enzymatic method and speeding up its application by pursuit of the following four specific aims.
Aim 1 is to expand the synthetic repertoire by evaluating new enzymes, mutants, and distinct donor and acceptor substrates for glycoprotein synthesis.
Aim 2 is to determine the crystal structures of EndoS and EndoF3, and their complexes with substrates/substrate analogs, which will provide a molecular level understanding of how these ENGases differentially recognize the substrates in hydrolysis and transglycosylation.
Aim 3 is to explore a two-step enzymatic strategy for direct glycosylation of polypeptides and proteins, including the study of N-glycosyltransferase (NGT) for directly introducing a monosaccharide primer into polypeptide and the subsequent extension of the sugar chains via ENGase-catalyzed transglycosylation.
Aim 4 is to remodel lysosomal enzymes with synthetic mannose 6-phosphate glycans aiming to enhance the therapeutic efficiency in enzyme replacement therapy (ERT). The proposed study is expected to provide important new tools in chemo enzymatic synthesis and the knowledge gained will speed up glycoprotein therapeutic applications.

Public Health Relevance

The proposed research aims at developing combined chemical and enzymatic methods for producing biologically important glycoproteins for functional studies. This study will provide new information on how glycosylation affects the functions of proteins and will speed up glycoprotein therapeutic applications.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Synthetic and Biological Chemistry A Study Section (SBCA)
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Marino, Pamela
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University of Maryland Baltimore
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Wang, Lai-Xi; Amin, Mohammed N (2014) Chemical and chemoenzymatic synthesis of glycoproteins for deciphering functions. Chem Biol 21:51-66
Trastoy, Beatriz; Lomino, Joseph V; Pierce, Brian G et al. (2014) Crystal structure of Streptococcus pyogenes EndoS, an immunomodulatory endoglycosidase specific for human IgG antibodies. Proc Natl Acad Sci U S A 111:6714-9
Orwenyo, Jared; Huang, Wei; Wang, Lai-Xi (2013) Chemoenzymatic synthesis and lectin recognition of a selectively fluorinated glycoprotein. Bioorg Med Chem 21:4768-77
Wang, Lai-Xi; Davis, Benjamin G (2013) Realizing the Promise of Chemical Glycobiology. Chem Sci 4:3381-3394
Wang, Helen; Huang, Wei; Orwenyo, Jared et al. (2013) Design and synthesis of glycoprotein-based multivalent glyco-ligands for influenza hemagglutinin and human galectin-3. Bioorg Med Chem 21:2037-44
Feng, Chiguang; Ghosh, Anita; Amin, Mohammed N et al. (2013) The galectin CvGal1 from the eastern oyster (Crassostrea virginica) binds to blood group A oligosaccharides on the hemocyte surface. J Biol Chem 288:24394-409
Lomino, Joseph V; Naegeli, Andreas; Orwenyo, Jared et al. (2013) A two-step enzymatic glycosylation of polypeptides with complex N-glycans. Bioorg Med Chem 21:2262-70
Wang, Lai-Xi; Lomino, Joseph V (2012) Emerging technologies for making glycan-defined glycoproteins. ACS Chem Biol 7:110-22
Fan, Shu-Quan; Huang, Wei; Wang, Lai-Xi (2012) Remarkable transglycosylation activity of glycosynthase mutants of endo-D, an endo-?-N-acetylglucosaminidase from Streptococcus pneumoniae. J Biol Chem 287:11272-81
Huang, Wei; Li, Jie; Wang, Lai-Xi (2011) Unusual transglycosylation activity of Flavobacterium meningosepticum endoglycosidases enables convergent chemoenzymatic synthesis of core fucosylated complex N-glycopeptides. Chembiochem 12:932-41

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