The enzyme Endoglycosidase H Endo N acetylglucosaminidase H, EC number 3.2.1.96 is a highly specific endoglycosidase which cleaves asparagine linked mannose rich oligosaccharides , but not highly processed complex oligosaccharides from glycoproteins . It is used for research purposes to deglycosylate glycoproteins. Structure and Activity Endoglycosidase H is isolated from Streptomyces plicatus or Streptomyces griseus . Its molecular weight is 29 000 Daltons. The primary structure is described by Robbins 1984 ref Robbins P. W., R. B. Trimble, D. F. Wirth, C. Hering, F.Maley , G. F. Maley, R. Das, B. W. Gibson, N. Royal and K. Biemann. Primary structure of the Streptomyces enzyme endo beta N acetylglucosaminidase H. J Biol Chem 259 7577 7583 1984 . ref Endoglycosidase H cleaves the bond in the diacetylchitobiose core of the oligosaccharide between two N acetylglucosamine GlcNAc subunits directly proximal to the asparagine residue, generating a truncated sugar molecule with one N acetylglucosamine residue remaining on the asparagine ref http www.acciusa.com pdfs northstar 100467 1.pdf Endoglycosidase H, North Star ref . It deglycosylates mannose glycoproteins, but the extent and rate of the deglycosylation depends to a high degree on the nature of the glycoproteins. The deglycosylation rate can be increased by denaturation of the glycoproteins e.g., by carboxymethylation, sulfitolysis or by heating in the presence of sodium dodecyl sulfate . Over 0.02 SDS may inactivate the enzyme. The addition of 0.1 M 2 mercaptoethanol highly increaases enzyme activity against glycoproteins containing inter or intramole cular disulfide bridges, unlike detergents like Triton X 100, n Octylglucoside, or zwitterionic detergents ref Trimble, R. B. & Maley, F. 1984 Anal. Biochem. 141, 515 522 ref . Biochemical Applications Endoglycosidase H Endo H is commonly used by cell biologists to monitor posttranslational modification in the Golgi apparatus . Most proteins destined for the cell su ... more details
and the importance of deglycosylation in their crystallization journal Eur. J. Biochem. volume 262 ... of receptor complexes of interleukin 10 stoichiometry and the importance of deglycosylation ... more details
TOCright Deoxyribozymes or DNA enzymes or catalytic DNA , or DNAzymes are deoxyribonucleic acid DNA molecules with catalyst catalytic action. In contrast to the RNA ribozyme that has many catalytic capabilities, DNA is only associated with gene DNA replication replication and nothing else. The reasons are that DNA lacks specific functional group s and that DNA prefers the double coil conformation in which potential catalytic sites are shielded. In comparison to protein s built up from 20 monomer s both RNA and DNA have a much more restricted set of monomers 4 to choose from which limits the construction of interesting catalytic sites. For these reasons DNAzymes exist only in the laboratory. Discovery The first deoxyribozyme was discovered in 1994 ref cite journal journal Chem Biol. year 1994 month December volume 1 issue 4 pages 223 9 title A DNA enzyme that cleaves RNA author Breaker RR, coauthors Joyce GF. pmid 9383394 doi 10.1016 1074 5521 94 90014 0 ref by current Yale Professor Ronald R. Breaker while a postdoctoral fellow in the laboratory of Prof. Gerald Joyce at The Scripps Research Institute in La Jolla, CA. This deoxyribozyme assists in lead ion dependent RNA cleaving operations. Catalytic amplification was found to be 100 fold compared to the uncatalysed reaction. Many other deoxyribozymes have since been developed that catalyse DNA phosphorylation, DNA adenylation , DNA deglycosylation , porphyrin metalation , thymine dimer photoreversion and DNA cleavage. Of particular interest are DNA ligase s ref cite journal title Deoxyribozymes DNA catalysts for bioorganic chemistry author Scott K. Silverman journal Org. Biomol. Chem. year 2004 volume 2 pages 2701 06 url http www.scs.uiuc.edu scott SilvermanPub30.pdf format PDF doi 10.1039 B411910J pmid 15455136 issue 19 ref . These molecules have demonstrated remarkable chemoselectivity in RNA branching reactions. Although each repeating unit in a RNA strand owns a free hydroxyl group, the DNA ligase takes just one ... more details
Encyclopedia
top
