Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.2.2.7 (heparinase)
 1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heparan sulfate biosynthesis initiates by the transfer of alpha-D-GlcNAc from UDP-GlcNAc to the D-GlcA moiety of the linkage tetrasaccharide, GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-core protein. The enzyme catalyzing this reaction differs from the alpha-GlcNAc transferase involved in chain polymerization based on genetic and enzymatic studies of an animal cell mutant defective in chain polymerization (Fritz, T. A., Gabb, M. M., Wei, G., and Esko, J. D. (1994) J. Biol. Chem. 269, 28809-28814). In this report we show that this mutant also accumulates a pentasaccharide intermediate containing alpha-GlcNAc. A fusion protein was made from the IgG-binding domain of protein A and a segment of the proteoglycan, betaglycan. This segment contained one glycosaminoglycan attachment site that primes only chondroitin sulfate and another that primes both heparan sulfate and chondroitin sulfate (Zhang, L., and Esko, J. D. (1994) J. Biol. Chem. 264, 19295-19299). Expression of the chimera in the mutant resulted in the accumulation of an oligosaccharide that labeled with [6-3H]GlcN. The oligosaccharide comigrated with a pentasaccharide standard derived from chondroitin sulfate, but acid hydrolysis gave 98% [3H]GlcN. Heparin lyase III digestion yielded [3H]GlcNAc, suggesting that the GlcNAc residue was alpha-linked to the nonreducing terminus. Enzymatic treatment of [6-3H]Gal-labeled material yielded the tetrasaccharide, delta GlcA-[3H]Gal-[3H]Gal-xylitol. These findings suggest that pentasaccharide had the structure, GlcNAc alpha 1-4GlcA beta 1-3Gal beta 1-3Gal beta 1-4Xyl. Its accumulation in a Chinese hamster ovary cell mutant defective in the polymerizing alpha-GlcNAc transferase provides in vivo evidence that two alpha-GlcNAc transferases catalyze the formation of heparan sulfate.
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PMID:Accumulation of a pentasaccharide terminating in alpha-N-acetylglucosamine in an animal cell mutant defective in heparan sulfate biosynthesis. 775 2

Pasteurella multocida Type D, a causative agent of atrophic rhinitis in swine and pasteurellosis in other domestic animals, produces an extracellular polysaccharide capsule that is a putative virulence factor. It was reported previously that the capsule was removed by treating microbes with heparin lyase III. We molecularly cloned a 617-residue enzyme, pmHS, which is a heparosan (nonsulfated, unepimerized heparin) synthase. Recombinant Escherichia coli-derived pmHS catalyzes the polymerization of the monosaccharides from UDP-GlcNAc and UDP-GlcUA. Other structurally related sugar nucleotides did not substitute. Synthase activity was stimulated about 7-25-fold by the addition of an exogenous polymer acceptor. Molecules composed of approximately 500-3,000 sugar residues were produced in vitro. The polysaccharide was sensitive to the action of heparin lyase III but resistant to hyaluronan lyase. The sequence of the pmHS enzyme is not very similar to the vertebrate heparin/heparan sulfate glycosyltransferases, EXT1 and 2, or to other Pasteurella glycosaminoglycan synthases that produce hyaluronan or chondroitin. The pmHS enzyme is the first microbial dual-action glycosyltransferase to be described that forms a polysaccharide composed of beta4GlcUA-alpha4GlcNAc disaccharide repeats. In contrast, heparosan biosynthesis in E. coli K5 requires at least two separate polypeptides, KfiA and KfiC, to catalyze the same polymerization reaction.
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PMID:Identification and molecular cloning of a heparosan synthase from Pasteurella multocida type D. 1175 62