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  • 1
    Electronic Resource
    Electronic Resource
    Inclusion of Cetaceans Within the Order Artiodactyla Based on Phylogenetic Analysis of Pancreatic Ribonuclease Genes (1999)
    Springer
    Journal of molecular evolution 48 (1999), S. 360-368 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Ribonuclease — Evolution — Cetacea — Artiodactyla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Mammalian secretory ribonucleases (RNases 1) form a family of extensively studied homologous proteins that were already used for phylogenetic analyses at the protein sequence level previously. In this paper we report the determination of six ribonuclease gene sequences of Artiodactyla and two of Cetacea. These sequences have been used with ruminant homologues in phylogenetic analyses that supported a group including hippopotamus and toothed whales, a group of ruminant pancreatic and brain-type ribonucleases, and a group of tylopod sequences containing the Arabian camel pancreatic ribonuclease gene and Arabian and Bactrian camel and alpaca RNase 1 genes of unknown function. In all analyses the pig was the first diverging artiodactyl. This DNA-based tree is compatible to published trees derived from a number of other genes. The differences to those trees obtained with ribonuclease protein sequences can be explained by the influence of convergence of pancreatic RNases from hippopotamus, camel, and ruminants and by taking into account the information from third codon positions in the DNA-based analyses. The evolution of sequence features of ribonucleases such as the distribution of positively charged amino acids and of potential glycosylation sites is described with regard to increased double-stranded RNA cleavage that is observed in several cetacean and artiodactyl RNases which may have no role in ruminant or ruminant-like digestion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006480
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  • 2
    Electronic Resource
    Electronic Resource
    Knowledge-based Homology Modeling and Experimental Determination of Amino Acid Side Chain Accessibility by the Laser Photo CIDNP (Chemically Induced Dynamic Nuclear Polarization) Approach in Solution: Lessons from the Small Sialidase of Clostridium perfringens (1996)
    Springer
    Journal of molecular modeling 2 (1996), S. 446-455 
    Details
    ISSN: 0948-5023
    Keywords: Sialidase ; NMR ; Protein modelling ; Molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The success of knowledge-based homology modelling is critically dependent on the predictive potency of the program structure-based calculations, which attempt to translate homologous sequences into three-dimensional structures, and on the actual relevance of the crystal structure for the protein topology. As quality control, experimental data for selected parameters of the protein′s conformation are required. Using the crystal structure of the sialidase of Salmonella typhimurium as framework for model building of the homologous enzyme from Clostridium perfringens, a set of energy-minimised conformers is derived. These proteins present e.g. Tyr, Trp and His residues with an assessable area on the surface, since the side chains of these amino acid residues are responsive to chemically induced dynamic nuclear polarization (CIDNP), monitored by NMR. Hence, as first lesson, a comparative analysis for model-derived and experimentally determined values can be performed. The second lesson of this study concerns the notable impact of single amino acid substitutions (Tyr/Phe, Cys/Ser) on the surface accessibility of the CIDNP-reactive amino acid side chains in mutant forms of the sialidase. Corroborating the predictions from the theoretical calculations, the spectra of the engineered mutants reveal marked and non-uniform alterations. Thus, the effect of apparently rather conservative amino acid substitutions on a distinct conformational aspect of this protein, even at distant sites, should not be underestimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089460020446
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of cysteine modifications on the activity of the ‘small’ Clostridium perfringens sialidase (1998)
    Springer
    Glycoconjugate journal 15 (1998), S. 767-775 
    Details
    ISSN: 1573-4986
    Keywords: sialidase ; mutagenesis ; cysteine modification ; mercury tolerance ; modulation of kinetic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The ‘small’ (43 kDa) sialidase of Clostridium perfringens is inhibited by low concentrations of mercury ions. For the investigation of possible functional roles of the enzyme's four cysteine residues at the amino acid positions 2, 282, 333 and 349, they were separately altered to serine by site-directed mutagenesis. The four mutant sialidases expressed in E. coli and purified by metal chelate chromatography were markedly reduced in specific activity when compared to the wild-type enzyme but with the exception of C282S exhibited similar KM-values indicating an unchanged mode of substrate binding. The substrate specificity was also conserved for C2S, C282S, and C333S. Only the C349S sialidase exhibited a higher relative activity with colominic acid and the α2,6-linked sialic acid of sialyllactose compared to the α2,3-linked isomer than the other mutants. Chemical modifications with the thiol-blocking reagents N-ethylmaleimide (NEM), p-chloromercuribenzoate (pCMB) and HgCl2 had little effect on the C282S sialidase, e.g., 6% inhibition by 5 m M NEM compared to reductions in activity between 65 and 90% for the wild-type and other mutant enzymes, supporting the idea that among the enzyme's cysteines, Cys-282 has the highest structural or functional significance. The results also explain the higher mercury tolerance of Salmonella typhimurium and Clostridium tertium sialidases, which have the positions equivalent to Cys-282 altered to Val and Thr, respectively, indicating that the thiol group of Cys-282, despite being situated near the active site, is not involved in catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006907931365
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of site-specific mutations on the enzymatic properties of a sialidase fromClostridium perfringens (1992)
    Springer
    Glycoconjugate journal 9 (1992), S. 235-240 
    Details
    ISSN: 1573-4986
    Keywords: sialidase (neuraminidase) ; site-specific mutations ; conserved sequences ; enzymatic properties ; Clostridium perfringens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three site-specific mutations were performed in two regions of a sialidase gene fromClostridium perfringens which are known to be conserved in bacterial sialidases. The mutant enzymes were expressed inEscherichia coli and, when measured with MU-Neu5Ac as substrate, exhibited variations in enzymatic properties compared with the wild-type enzyme. The conservative substitution of Arg 37 by Lys, located in a short conserved region upstream from the four repeated sequences common in bacterial sialidase genes, was of special interest, asK M andV max, as well asK i measured with Neu5Ac2en, were dramatically changed. These data suggest that this residue may be involved in substrate binding. In addition to its low activity, this mutant enzyme has a lower temperature optimum and is active over a more limited pH range. This mutation also prevents the binding of an antibody able to inhibit the wild-type sialidase. The other mutations, located in one of the consensus sequences, were of lower influence on enzyme activity and recognition by antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731135
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  • 5
    Electronic Resource
    Electronic Resource
    Studies on the inhibition of sialyl- and galactosyltransferases (1997)
    Springer
    Glycoconjugate journal 14 (1997), S. 57-66 
    Details
    ISSN: 1573-4986
    Keywords: sialyltransferase ; galactosyltransferase ; inhibitor ; nucleoside monosaccharide conjugates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The inhibition of the α-2,6-sialyltransferase from rat liver, the α-2,3-sialyltransferase from porcine submandibular gland and of the galactosyltransferase from human milk were studied using monosaccharide-, nucleoside- and nucleotide-derivatives of their naturally occurring donor substrates cytidine 5′-monophosphate-N-acetylneuraminic acid and uridine 5′-diphosphate-galactose, respectively. Only the corresponding nucleosides/nucleotides showed inhibitory activity. Periodate oxidation of CMP or CMP-Neu5Ac and of UMP or UDP-Gal led to reduced inhibitory efficiency with the respective transferase. The type and reversibility of the inhibition of some of these compounds, as well as the corresponding Ki values were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018560931389
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  • 6
    Electronic Resource
    Electronic Resource
    Purification and characterization of a sialidase fromClostridium chauvoei NC08596 (1991)
    Springer
    Glycoconjugate journal 8 (1991), S. 95-101 
    Details
    ISSN: 1573-4986
    Keywords: sialidase (neuraminidase) ; purification ; properties ; Clostridum chauvoei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sialidase secreted byClostridium chauvoei NC08596 was purified to apparent homogeneity by ion-exchange chromatography, gel filtration, hydrophobic interaction-chromatography, FPLC ion-exchange chromatography, and FPLC gel filtration. The enzyme was enriched about 10 200-fold, reaching a final specific activity of 24.4 U mg−1. It has a relatively high molecular mass of 300 kDa and consists of two subunits each of 150 kDa. The cations Mn2+, Mg2+, and Ca2+ and bovine serum albumin have a positive effect on the sialidase activity, while Hg2+, Cu2+, and Zn2+, chelating agents and salt decrease enzyme activity. The substrate specificity, kinetic data, and pH optimum of the enzyme are similar to those of other bacterial sialidases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731018
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  • 7
    Electronic Resource
    Electronic Resource
    Indications for the enzymatic synthesis of 9-O-lactoyl-N-acetylneuraminic acid in equine liver (1993)
    Springer
    Glycoconjugate journal 10 (1993), S. 116-119 
    Details
    ISSN: 1573-4986
    Keywords: 9-O-Lactoyl-N-acetylneuraminic acid ; equine liver ; enzymatic synthesis ; sialic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fractionation of horse liver homogenate by centrifugation into heavy membranes at 10 000 × g, microsomal fraction at 105 000 × g, and the supernatant revealed sialate 9-O-lactoyltransferase activity only in the latter fraction. For the enzyme assay, the various fractions were incubated with14C labelled CMP-N-acetylneuraminic acid,N-acetylneuraminic acid and glycoconjugate-boundN-acetylneuraminic acid. Lactoylation was identified in three different TLC systems after acid hydrolysis and purification of the sialic acids in the incubation mixtures. Enzyme activity was found only in the supernatant fraction. Glycoconjugate-boundN-acetylneuraminic acid was the best substrate tested, although some lactoylation was also found when using CMP-N-acetylneuraminic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731195
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  • 8
    Electronic Resource
    Electronic Resource
    Carbohydrate-protein interaction studies by laser photo CIDNP NMR methods (1997)
    Springer
    Glycoconjugate journal 14 (1997), S. 531-534 
    Details
    ISSN: 1573-4986
    Keywords: Chemically induced dynamic nuclear polarization (CIDNP) ; carbohydrate-protein interaction ; NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The side chains of tyrosine, tryptophan and histidine are able to produce CIDNP (Chemically Induced Dynamic Nuclear Polarization) signals after laser irradiation in the presence of a suitable radical pair-generating dye. Elicitation of such a response in proteins implies surface accessibility of the respective groups to the light-absorbing dye. In principle, this technique allows the monitoring of the effect of ligand binding to a receptor and of site-directed mutagenesis on conformational aspects of any protein if CIDNP-reactive amino acids are involved. The application of this method in glycosciences can provide insights into the protein-carbohydrate interaction process, as illustrated in this initial model study for several N-acetyl-glucosamine-binding lectins of increasing structural complexity as well as for a wild type bacterial sialidase and its mutants. Experimentally, the shape and intensity of CIDNP signals are determined in the absence and in the presence of specific glycoligands. When the carbohydrate is bound, CIDNP signals of side chain protons of tyrosine, tryptophan or histidine residues can be broadened and of reduced intensity. This is the case for hevein, pseudo-hevein, the four hevein domains-containing lectin wheat germ agglutinin (WGA) and the cloned B-domain of WGA 1 (domB) representing one hevein domain. This response indicates either a spatial protection by the ligand or a ligand-induced positioning of formerly surface-exposed side chains into the protein’s interior part, thereby precluding interaction with the photo-activated dye. Some signals of protons from the reactive side chains can even disappear when the lectin-ligand complexes are monitored. The ligand binding, however, can apparently also induce a conformational change in a related lectin that causes the appearance of a new signal, as seen for Urtica dioica agglutinin (UDA) which consists of two hevein domains. Additionally, the three CIDNP-reactive amino acids are used as sensors for the detection of conformational changes caused by pH variations or by deliberate amino acid exchanges, as determined for the isolectins hevein and pseudo-hevein as well as for the cloned small sialidase of Clostridium perfringens and two of its mutants. Therefore, CIDNP has proven to be an excellent tool for protein-carbohydrate binding studies and can be established in glycosciences as a third biophysical method beside X-ray-crystallography and high-resolution multidimensional NMR studies which provides reliable information of certain structural aspects of carbohydrate-binding proteins in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018572023153
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  • 9
    Electronic Resource
    Electronic Resource
    Structural Variations of N-Acetylneuraminic Acid, 10. Synthesis of 2,7-, 2,8-, and 2,9-Dideoxy- and 2,4,7-Trideoxy-2,3-didehydro-N-acetylneuraminic Acids and Their Behavior Towards Sialidase from Vibrio cholerae (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 159-165 
    Details
    ISSN: 0170-2041
    Keywords: N-Acetylneuraminic acid ; Sialidase ; Vibrio cholerae ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Strukturelle Abwandlungen an N-Acetylneuraminsäure, 101). - Synthese von 2,7-, 2,8- und 2,9-Didesoxy- und 2,4,7-Tridesoxy-2,3-didehydro-N-acetylneuraminsäure und ihr Verhalten gegenüber Sialidase aus Vibrio choleraeDie peracetylierten Methylester-Derivate von 7-Desoxy-Neu5Ac (2c), 8-Desoxy-Neu5Ac (3a), 9-Desoxy-Neu5Ac (4a) und 4,7-Didesoxy-Neu5Ac (5a) wurden mit Trifluormethansulfonsäuretrimethylsilylester in die entsprechenden 2-Desoxy-2,3-didehydro-Derivate 2b-5b umgewandelt, wobei auch in wechselnder Menge die 4,5-Oxazolino-Abkömmlinge 6b-8b gebildet wurden. Hydrolyse von 2b-5b führte zu den freien Säuren 7-Desoxy-Neu5Ac2en (2c), 8-Desoxy-Neu5Ac2en (3c), 9-Desoxy-Neu5Ac2en (4c) und 4,7-Didesoxy-Neu5Ac2en (5c). Diese hemmen die Hydrolyse von 4-Methylumbelliferyl-α-Neu5Ac durch Sialidase aus Vibrio cholerae in einem signifikant unterschiedlichen Ausmaß. Der Vergleich ihrer ermittelten α-Seitenprofile mit demjenigen von Neu5Ac2en ermöglicht ein Verständnis für den sehr unterschiedlichen Einfluß auf die Enzymreaktion.
    Notes: The peracetylated methyl ester derivatives of 7-deoxy-Neu5Ac (2a), 8-deoxy-Neu5Ac (3a, 9-deoxy-Neu5Ac (4a), and 4,7-dideoxy-Neu5Ac (5a) were transformed by trimethylsilyl trifluoromethanesulfonate into the corresponding 2-deoxy-2,3-didehydro derivatives 2b-5b. As additional products, the 4,5-oxazolino derivatives 6b-8b were formed. Hydrolysis of 2b-5b yielded the free acids 7-deoxy-Neu5Ac2en (2c), 8-deoxy-Neu5Ac2en (3c), 9-deoxy-Neu5Ac2en (4c), and 4,7-dideoxy-Neu5Ac2en (5c). They showed significantly different inhibitory influences on the hydrolysis of 4-methylumbelliferyl-α-Neu5Ac by sialidase from Vibrio cholerae. The comparison of their evaluated α-side profiles with that of Neu5Ac2en (1c) enables a suitable explanation of their different inhibitory potencies.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890131
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  • 10
    Electronic Resource
    Electronic Resource
    Structural Variations of N-Acetylneuraminic Acid, 11, Synthesis of the 4-Methylumbelliferyl 2α-Glycosides of 7-Epi-, 8-Epi-, and 7,8-Bis(epi)-N-acetylneuraminic Acids, as well as of 7-Deoxy-, 8-Deoxy-, 9-Deoxy-, and 4,7-Dideoxy-N-acetylneuraminic Acids and Their Behaviour Towards Sialidase from Vibrio cholerae (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 519-526 
    Details
    ISSN: 0170-2041
    Keywords: Sialic acid analogues ; Sialidase ; Vibrio cholerae ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Strukturelle Abwandlungen an N-Acetylneuraminsäure, 111). - Synthese der 4-Methylumbelliferyl-2α-glycoside von 7-Epi-, 8-Epi-und 7,8-Bis(epi)-N-acetylneuraminsäuren, sowie von 7-Desoxy-, 8-Desoxy-, 9-Desoxy- und 4,7-Didesoxy-N-acetylneuraminsäure und ihr Verhalten gegenüber Vibrio-cholerae-SialidaseDie Methylester von 7-Epi-Neu5Ac (1a), 8-Epi-Neu5Ac (2a), 7,8-Bis(epi)-Neu5Ac (3a), 7-Desoxy-Neu5Ac (4a), 8-Desoxy-Neu5Ac (5a), 9-Desoxy-Neu5Ac (6a) und 4,7-Didesoxy-Neu5Ac (7a) wurden in die peracetylierten Gemische der α- und β-Anomeren 1b-7b und 1c-7c umgewandelt. Aus den mit Acetylchlorid/HCl hergestellten 2-Chlorderivaten wurden in der folgenden Königs-Knorr-Reaktion mit 4-Methylumbelliferon (MU) die entsprechenden Methylumbelliferyl-2α-glycoside 7-Epi-Neu-4,5,7,8,9Ac51Me-αMU (1d), 8-Epi-Neu4,5,7,8,9Ac51Me-αMU (2d), 7,8-Bis(epi)-Neu4,5,7,8,9Ac51Me-αMU (3d), 7-Desoxy-Neu-4,5,8,9Ac41Me-αMU (4d), 8-Desoxy-Neu4,5,7,9Ac41Me-αMU (5d), 9-Desoxy-Neu4,5,7,8Ac41Me-αMU (6d) und 4,7-Didesoxy-Neu5,8,9Ac31Me-αMU (7d) hergestellt. Im letztgenannten Fall entstand auch das β-Anomere von 4,7-Didesoxy-Neu5,8,9-Ac31Me-βMU (7d′)- Zemplen-Verseifung und darauffolgende Hydrolyse der Estergruppe mit wäßrigem Natriumhydroxyd lieferte die Natriumsalze der MU-2α-Glycoside von 7-Epi-, 8-Epi-, 7,8-Bis(epi)-, 7-Desoxy-, 8-Desoxy-, 9-Desoxy- und 4,7-Didesoxy-Neu5Ac-MU 1e-7e. Die enzymatische Hydrolyse dieser Verbindungen mit Sialidase aus Vibrio cholerae zeigte nur für 3e und 7e signifikant verminderte Spaltungsgeschwindigkeiten, welche mit den Inhibitorkonstanten Ki von 7,8-Bis(epi)-Neu5Ac2en und 4,7-Didesoxy-Neu5Ac2en korrelierbar sind1,15).
    Notes: The methyl esters of 7-epi-Neu5Ac (1a), 8-epi-Neu5Ac (2a), 7,8-bis(epi)-Neu5Ac (3a), 7-deoxy-Neu5Ac (4a), 8-deoxy-Neu5Ac (5a), 9-deoxy-Neu5Ac (6a), and 4,7-dideoxy-Neu5Ac (7a) were transformed into their peracetylated mixtures of the α-anomers 1b-7b and β-anomers 1c-7c. In the next step the 2-Cl derivatives were prepared with acetyl chloride/HCl which yielded in the following Königs-Knorr reaction with 4-methylumbelliferone (MU) the corresponding methylumbelliferyl 2α-glycosides 7-epi-Neu4,5,7,8,9Ac51Me-αMU (1d), 8-epi-Neu4,5,7,8,9Ac51Me-αMU (2d), 7,8-bis(epi)-Neu4,5,7,8,9Ac51Me-αMU (3d), 7-deoxy-Neu-4,5,8,9Ac41Me-αMU (4d), 8-deoxy-Neu4,5,7,9Ac41Me-αMU (5d), 9-deoxy-Neu4,5,7,8A41Me-αMU (6d), and 4,7-dideoxy-Neu-5,8,9Ac31Me-αMU (7d). In the last case also the β-anomer of 4,7-dideoxy-Neu5,8,9Ac31Me-βMU (7d′) was formed. Zemplen saponification followed by hydrolysis of the ester group with sodium hydroxide, resulted in the sodium salts of the sialic acid MU 2α-glycosides 7-epi-, 8-epi-, 7,8-bis(epi)-, 8-deoxy-, 9-deoxy- and 4,7-dideoxy-Neu5Ac-MU 1e-7e. The enzymatic hydrolysis of these compounds with sialidase from Vibrio cholerae showed only for 3e and 7e significantly reduced rates of cleavage, which is in agreement with the inhibitor constants Ki of the related 2,3-didehydro sialic acids 7,8-bis(epi)-Neu5Ac2en and 4,7-dideoxy-Neu5Ac2en1,15).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890192
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