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  • 1
    Electronic Resource
    Electronic Resource
    Control of mucin synthesis: the peptide portion of synthetic O-glycopeptide substrates influences the activity of O-glycan core 1 uridine 5'-diphospho-galactose:N-acetyl-.alpha.-galactosaminyl-.alpha.-R .beta.3-galactosyltransferase (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 10206-10212 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00496a008
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  • 2
    Electronic Resource
    Electronic Resource
    Control of glycoprotein synthesis: substrate specificity of rat liver UDP-GlcNAc:Manα3R β2-N-acetylglucosaminyl-transferase I using synthetic substrate analogues (1992)
    Springer
    Glycoconjugate journal 9 (1992), S. 180-190 
    Details
    ISSN: 1573-4986
    Keywords: GlcNAc-transferase I ; substrate specificity ; glycoprotein biosynthesis ; N-linked glycans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc: Manα3R β2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) is the key enzyme in the synthesis of complex and hybrid N-glycans. Rat liver GlcNAc-T I has been purified more than 25,000-fold (M r 42,000). TheV max for the pure enzyme with [Manα6(Manα3)Manα6](Manα3)Manβ4GlcNAcβ4GlcNAcβ-Asn as substrate was 4.6 µmol min−1 mg−1. Structural analysis of the enzyme product by proton nuclear magnetic resonance spectroscopy proved that the enzyme adds anN-acetylglucosamine (GlcNAc) residue in β1–2 linkage to the Manα3Manβ-terminus of the substrate. Several derivatives of Manα6(Manα3)Manβ-R, a substrate for the enzyme, were synthesized and tested as substrates and inhibitors. An unsubstituted equatorial 4-hydroxyl and an axial 2-hydroxyl on the β-linked mannose of Manα6(Manα3)Manβ-R are essential for GlcNAc-T I activity. Elimination of the 4-hydroxyl of the α3-linked mannose (Man) of the substrate increases theK M 20-fold. Modifications on the α6-linked mannose or on the core structure affect mainly theK M and to a lesser degree theV max, e.g., substitutions of the Manα6 residue at the 2-position by GlcNAc or at the 3- and 6-positions by mannose lower theK M, whereas various other substitutions at the 3-position increase theK M slightly. Manα6(Manα3)4-O-methyl-Manβ4GlcNAc was found to be a weak inhibitor of GlcNAc-T I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731163
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  • 3
    Electronic Resource
    Electronic Resource
    Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme (1994)
    Springer
    Glycoconjugate journal 11 (1994), S. 210-216 
    Details
    ISSN: 1573-4986
    Keywords: Synthetic oligosaccharides ; inhibitors ; N-glycans ; N-acetylglucosaminyltransferase ; biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complexN-glycans. We have tested a series of synthetic analogues of the substrate Man‴α1-6(GlcNAc″β1-2Man′α1-3)Manβ-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attachesN-acetylglucosamine in β1-2 linkage to the 2‴-OH of the Man‴α1-6 residue. The 2‴-deoxy analogue is a competitive inhibitor (K i=0.13mm). The 2‴-O-methyl compound does not bind to the enzyme presumably due to steric hindrance. The 3‴-, 4‴- and 6‴-OH groups are not essential for binding or catalysis since the 3‴-, 4‴- and 6‴-deoxy and -O-methyl derivatives are all good substrates. Increasing the size of the substituent at the 3‴-position to pentyl and substituted pentyl groups causes competitive inhibition (K i=1.0–2.5mm). We have taken advantage of this effect to synthesize two potentially irreversible GlcNAc-T II inhibitors containing a photolabile 3‴-O-(4,4-azo)pentyl group and a 3‴-O-(5-iodoacetamido)pentyl group respectively. The data indicate that none of the hydroxyls of the Man‴α1-6 residue are essential for binding although the 2‴- and 3‴-OH face the catalytic site of the enzyme. The 4-OH group of the Manβ-O-octyl residue is not essential for binding or catalysis since the 4-deoxy derivative is a good substrate; the 4-O-methyl derivative does not bind. This contrasts with GlcNAc-T I which cannot bind to the 4-deoxy-Manβ- substrate analogue. The data are compatible with our previous observations that a ‘bisecting’N-acetylglucosamine at the 4-OH position prevents both GlcNAc-T I and GlcNAc-T II catalysis. However, in the case of GlcNAc-T II, the bisectingN-acetylglucosamine prevents binding due to steric hindrance rather than to removal of an essential OH group. The 3′-OH of the Man′α1-3 is an essential group for GlcNAc-T II since the 3′-deoxy derivative does not bind to the enzyme. The trisaccharide GlcNAcβ1-2Manα1-3Manβ-O-octyl is a good inhibitor (K i=0.9mm). The above data together with previous studies indicate that binding of the GlcNAcβ1-2Manβ1-3Manβ- arm of the branched substrate to the enzyme is essential for catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731220
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  • 4
    Electronic Resource
    Electronic Resource
    Structure of the gene for the human 17β-hydroxysteroid dehydrogenase type IV (1998)
    Springer
    Mammalian genome 9 (1998), S. 1036-1041 
    Details
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The 17β-hydroxysteroid dehydrogenase type IV (17β-HSD IV) is a multifunctional enzyme that is localized in the peroxisomes. The N-terminal part has dehydrogenase activity, the central part has hydratase activity, and the carboxy-terminal part is responsible for sterol transport. Recent observations of mutations in the human 17β-HSD IV cDNA leading to a severe peroxisomal disorder motivated us to define the genomic organization of this gene mapped to Chromosome (Chr) 5q2. We show here that this gene consist of 24 exons and 23 introns with classical intron-exon junctions spanning more than 100 kbp. By mapping the regulatory region of this gene, we have shown that the first 400 bp upstream of the transcription start site are sufficient to activate transcription. The data presented here will permit sequence analysis of patients with peroxisomal disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003359900921
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