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At least 613 records · Page 34Linked to original sources
PubMed2005

New glycosidase activated nitric oxide donors: glycose and 3-morphorlinosydnonimine conjugates.

[reaction: see text] To achieve site specific delivery of nitric oxide (NO), a new class of glycosidase activated NO donors has been developed. Glucose, galactose, and N-acetylneuraminic acid were covalently coupled to 3-morphorlinosydnonimine (SIN-1), a mesoionic heterocyclic NO donor, via a carbamate linkage at the anomeric position. The beta-glycosides were successfully prepared for these conjugates, while the alpha-glycosidic compounds were very unstable. The new stable sugar-NO conjugates could release NO in the presence of glycosidases. Such NO prodrugs may be used as enzyme activated NO donors in biomedical research.

Catalysis↗
PubMed2000

Synthesis of 2-substituted polyhydroxytetrahydropyrimidines (N-hydroxy cyclic guanidino-sugars): transition-state mimics of enzymatic glycosidic cleavage.

The synthesis of 2'-substituted polyhydroxytetrahydropyrimidines as transition-state mimics of enzymatic glycosidic cleavage has been achieved by using guanylation and cyclization methodologies. The D-galacto type N-hydroxy cyclic guanidino-sugar 21 was synthesized in six steps from amine 7 and thiourea 14 in an overall yield of 59%. To further derivatize compound 21 to incorporate the leaving group moiety, we have synthesized 2-methylsulfanyl compounds 26-29 as key intermediates. The 2-methylsulfanyl group in 29 was displaced with amines, assisted by silver tetrafluoroborate as Lewis acid, to give protected cyclic guanidines 30-32 in moderate yields (60-67%). Removal of the protecting groups in 32 gave the D-galacto-type N-hydroxy cyclic guanidino-sugar 34. The key steps in the synthesis of the 6-deoxy-DL-galacto type N-hydroxy cyclic guanidino-sugars 49, 54, and 64-66 involve cyclization of the appropriate acetal intermediates (45, 50, and 58-60) followed by removal of the protecting groups.

Crystallography, X-Ray↗
PubMed2000

Stereoselective inhibition of alpha-L-fucosidases by N-benzyl aminocyclopentitols.

[structure: see text] (1R,2R,3R,4R,5R)-4-Amino-5-methylcyclopentane-1,2,3 -tr iol 8, its 4S stereoisomer 9, and their acyclic analogues (R)- and (S)-2-aminobutanol 11 and 12 are selective but moderate inhibitors of alpha-L-fucosidases. N-Benzylation selectively enhances inhibition potency for aminocyclopentitol 8 (--> 1, K(i) = 6.8 x 10(-)(7) M) but decreases inhibition for its 4S-stereoisomer 9 (--> 2, K(i) = 1.1 x 10(-)(4) M) and for the aminobutanols 11 (--> 13, no inhibition) and 12 (--> 14, no inhibition).

Amino Alcohols↗
PubMed2004

Biotransformation of quinovic acid glycosides by microbes: direct conversion of the ursane to the oleanane triterpene skeleton by Nocardia sp. NRRL 5646.

[reaction: see text] Quinovic acid glycosides were microbially deglycosylated by a Nocardia sp. to their aglycon quinovic acid and its biogenetic counterpart, cincholic acid (3), via an unprecedented carbon skeleton rearrangement involving a methyl group migration. The structures of the metabolites were established by ESI-LC/MS and 2D-NMR techniques.

Biotransformation↗
PubMed2005

Relevance of the glycosyl donor to the regioselectivity of glycosidation of primary-secondary diol acceptors and application of these ideas to in situ three-component double differential glycosidation.

[reaction: see text] Three pairs of primary-secondary diol acceptors have been exposed to armed, disarmed, and n-pentenyl ortho ester glycosyl donors in glycosidation reactions. It is shown that the regioselectivity of those glycosylations is greatly influenced by the armed, disarmed, or ortho ester nature of the glycosyl donors. The selectivities observed have been used to devise efficient in situ three-component glycosylations involving two donors and one acceptor.

Alcohols↗
PubMed2003

Cloning of a gene encoding a thermo-stable endo-beta-1,4-glucanase from Thermoascus aurantiacus and its expression in yeast.

A gene encoding a thermo-stable endo-beta-1,4-glucanase was isolated from the thermophilic fungus, Thermoascus aurantiacus IFO9748, and designated as eg1. Induction of this gene expression at 50 degrees C was stronger than at 30 degrees C. The deduced amino acid sequence encoded by eg1 showed that it belongs to the glycoside hydrolase family 5. The cloned gene was expressed in Saccharomyces cerevisiae and the gene product was purified and characterized. No significant activity loss was detected over 2 h at 70 degrees C and the product was stable from pH 3-10. The enzyme was optimally active at 70 degrees C over 20 min and the optimal pH was 6.

Cells, Cultured↗
PubMed2004

Cellulase complex of the fungus Chrysosporium lucknowense: isolation and characterization of endoglucanases and cellobiohydrolases.

Using different chromatographic techniques, eight cellulolytic enzymes were isolated from the culture broth of a mutant strain of Chrysosporium lucknowense: six endoglucanases (EG: 25 kD, pI 4.0; 28 kD, pI 5.7; 44 kD, pI 6.0; 47 kD, pI 5.7; 51 kD, pI 4.8; 60 kD, pI 3.7) and two cellobiohydrolases (CBH I, 65 kD, pI 4.5; CBH II, 42 kD, pI 4.2). Some of the isolated cellulases were classified into known families of glycoside hydrolases: Cel6A (CBH II), Cel7A (CBH I), Cel12A (EG28), Cel45A (EG25). It was shown that EG44 and EG51 are two different forms of one enzyme. EG44 seems to be a catalytic module of an intact EG51 without a cellulose-binding module. All the enzymes had pH optimum of activity in the acidic range (at pH 4.5-6.0), whereas EG25 and EG47 retained 55-60% of the maximum activity at pH 8.5. Substrate specificity of the purified cellulases against carboxymethylcellulose (CMC), beta-glucan, Avicel, xylan, xyloglucan, laminarin, and p-nitrophenyl-beta-D-cellobioside was studied. EG44 and EG51 were characterized by the highest CMCase activity (59 and 52 U/mg protein). EG28 had the lowest CMCase activity (11 U/mg) amongst the endoglucanases; however, this enzyme displayed the highest activity against beta-glucan (125 U/mg). Only EG51 and CBH I were characterized by high adsorption ability on Avicel cellulose (98-99%). Kinetics of Avicel hydrolysis by the isolated cellulases in the presence of purified beta-glucosidase from Aspergillus japonicus was studied. The hydrolytic efficiency of cellulases (estimated as glucose yield after a 7-day reaction) decreased in the following order: CBH I, EG60, CBH II, EG51, EG47, EG25, EG28, EG44.

Adsorption↗
PubMed2004

Members of a new group of chitinase-like genes are expressed preferentially in cotton cells with secondary walls.

Two homologous cotton (Gossypium hirsutum L.) genes, GhCTL1 and GhCTL2, encode members of a new group of chitinase-like proteins (called the GhCTL group) that includes other proteins from two cotton species, Arabidopsis, rice, and pea. Members of the GhCTL group are assigned to family GH19 glycoside hydrolases along with numerous authentic chitinases (http://afmb.cnrs-mrs.fr/CAZY/index.html), but the proteins have novel consensus sequences in two regions that are essential for chitinase activity and that were previously thought to be conserved. Maximum parsimony phylogenetic analyses, as well as Neighbor-Joining distance analyses, of numerous chitinases confirmed that the GhCTL group is distinct. A molecular model of GhCTL2 (based on the three-dimensional structure of a barley chitinase) had changes in the catalytic site that are likely to abolish catalytic activity while retaining potential to bind chitin oligosaccharides. RNA blot analysis showed that members of the GhCTL group had preferential expression during secondary wall deposition in cotton lint fiber. Cotton transformed with a fusion of the GhCTL2 promoter to the beta -d-glucuronidase gene showed preferential reporter gene activity in numerous cells during secondary wall deposition. Together with evidence from other researchers that mutants in an Arabidopsis gene within the GhCTL group are cellulose-deficient with phenotypes indicative of altered primary cell walls, these data suggest that members of the GhCTL group of chitinase-like proteins are essential for cellulose synthesis in primary and secondary cell walls. However, the mechanism by which they act is more likely to involve binding of chitin oligosaccharides than catalysis.

Amino Acid Sequence↗
PubMed2006

Structure and mechanism of a bacterial beta-glucosaminidase having O-GlcNAcase activity.

O-GlcNAc is an abundant post-translational modification of serine and threonine residues of nucleocytoplasmic proteins. This modification, found only within higher eukaryotes, is a dynamic modification that is often reciprocal to phosphorylation. In a manner analogous to phosphatases, a glycoside hydrolase termed O-GlcNAcase cleaves O-GlcNAc from modified proteins. Enzymes with high sequence similarity to human O-GlcNAcase are also found in human pathogens and symbionts. We report the three-dimensional structure of O-GlcNAcase from the human gut symbiont Bacteroides thetaiotaomicron both in its native form and in complex with a mimic of the reaction intermediate. Mutagenesis and kinetics studies show that the bacterial enzyme, very similarly to its human counterpart, operates via an unusual 'substrate-assisted' catalytic mechanism, which will inform the rational design of enzyme inhibitors.

Acetylglucosaminidase↗
PubMed2026

Polyphasic taxonomic characterization of Brachybacterium netajii sp. nov., a metabolically versatile bacterium isolated from the river Ganges, India.

A comprehensive polyphasic taxonomic strategy was applied to the systematic characterization of strain DNPG3T, which was isolated from the river Ganges, Hooghly, West Bengal, India. The Gram-positive, halotolerant, heavy-metal-tolerant strain exhibited the ability to degrade p-nitrophenol (PNP). Cellular fatty acid analysis revealed that the predominant components were anteiso-C15:0 (24.61%), C11:0 (21.06%), iso-C16:0 (11.89%), C16:0 (11.58%), and anteiso-C17:0 (11.24%). Notably, the presence of C11:0, C10:0 2-OH as major fatty acids differentiate strain DNPG3T from its closely related members of the genus Brachybacterium. The predominant respiratory quinone was identified as menaquinone-7 (MK-7). Analysis of 16S rRNA gene sequence indicated that B. zhongshanense strain JBT was the closest relative of DNPG3T, sharing 97.08% sequence similarity. Genome-based ANI value calculated using the EzBioCloud server revealed that B. zhongshanense JCM 15471T was the closest genomic relative (85.49%). These values were further substantiated by digital DNA-DNA hybridization (dDDH) estimates calculated using the GGDC server. Taxonomic assignment using the GTDB database further indicated that strain DNPG3T constitutes a previously unrecognized species within the genus Brachybacterium. Genome analysis of strain DNPG3T identified eleven genomic islands, along with a rich repertoire of 194 carbohydrate-active enzyme (CAZyme) families, comprising 95 glycoside hydrolases and 53 glycosyltransferases. In addition, five biosynthetic gene clusters were detected. Collectively, these genomic features indicate the involvement of horizontal gene transfer events and highlighted the pronounced metabolic versatility of the strain, underscoring its potential for industrial enzyme production and secondary metabolite biosynthesis. Pan-genome analysis further indicates that the Brachybacterium pan-genome is open, reflecting substantial genetic diversity and ongoing gene acquisition within the genus. Comprehensive biochemical, physiological, chemotaxonomic, and phylogenetic analyses supported the assignment of strain DNPG3T to the genus Brachybacterium while clearly distinguishing it from all currently described species within the genus. Accordingly, strain DNPG3T was proposed to represent a novel species, for which the name Brachybacterium netajii sp. nov. is suggested. The type strain was DNPG3T (= MTCC13125T).

India↗
PubMed2003

Enzymic, spectroscopic and calorimetric studies of a recombinant dextranase expressed in Pichia pastoris.

Conformational stability and structural characterization of an rDex (recombinant dextranase) expressed in Pichia pastoris were studied by enzymic assays, fluorescence, CD and DSC (differential scanning calorimetry). We also identified two disulphide bridges (Cys9-Cys14, Cys484-Cys488) and two free Cys residues (Cys336, Cys415) that are not conserved between bacterial and fungal dextranases of GH-49 (glycoside hydrolase family 49) by MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS. Enzymic and fluorescence studies revealed that rDex is biological and conformationally stable at acidic pH, with maximum activity at pH 4.5-5.0, while CD spectra indicated a secondary structure basically composed of beta-sheets. rDex loses biological activity at neutral pH without total disruption of its conformation. In addition, rDex preserves its conformation close to 60 degrees C, but it is thermally denatured with appreciable aggregation at temperatures above 75 degrees C. DSC studies always displayed irreversible transitions and a strong dependence on the scan rate. Our combined analysis suggested that the denaturation process of rDex is under kinetic control, which is described reasonably well by the two-state kinetic scheme.

Amino Acid Sequence↗
PubMed1967

The hydrolysis of glycosyl fluorides by glycosidases.

1. alpha-d- and beta-d-Glucopyranosyl, alpha-d- and beta-d-galactopyranosyl, alpha-d-mannopyranosyl and alpha-d-xylopyranosyl fluorides were hydrolysed specifically by the respective glycosidases from several sources. 2. Use of specific inhibitors with a mixture of glycosidases from Helix pomatia intestinal juice showed that each glycosyl fluoride was hydrolysed only by the respective glycosidase. alpha-d-Glucopyranosidase and alpha-d-xylopyranosidase activities were shown to be due to different enzymes. 3. Partially purified enzyme preparations containing only one of the glycosidase activities hydrolysed only the corresponding glycosyl fluoride. 4. The configuration at C-1 of alpha-d-mannopyranosyl fluoride was confirmed since it was hydrolysed by an alpha-d-mannosidase preparation that contained no detectable beta-d-mannosidase activity. 5. An attempt to prepare o-nitrophenyl beta-d-mannopyranoside led only to o-nitrophenyl alpha-d-mannopyranoside.

Animals↗