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At least 1,333 records · Page 74Linked to original sources
PubMed2000

Inverting character of alpha-glucuronidase A from Aspergillus tubingensis.

Alpha-glucuronidase A from Aspergillus tubingensis was found to be capable of liberating 4-O-methyl-D-glucuronic acid (MeGlcA) only from those beechwood glucuronoxylan fragments in which the acid is attached to the non-reducing terminal xylopyranosyl residue. Reduced aldotetrauronic acid, 4-O-methyl-D-glucuronosyl-alpha-1,2-D-xylopyranosyl-beta-1,4-xylopyranosyl-beta-1,4-xylitol, was found to be a suitable substrate to follow the stereochemical course of the hydrolytic reaction catalyzed by the purified enzyme. The configuration of the liberated MeGlcA was followed in a D(2)O reaction mixture by (1)H-NMR spectroscopy. It was unambiguously established that MeGlcA was released from the substrate as its beta-anomer from which the alpha-anomer was formed on mutarotation. This result represents the first experimental evidence for the inverting character of a microbial alpha-glucuronidase, a member of glycosyl hydrolase family 67 (EC 3.1.1.139).

Aspergillus↗
PubMed2003

Molecular cloning of the gene for 2,6-beta-D-fructan 6-levanbiohydrolase from Streptomyces exfoliatus F3-2.

The gene encoding a 2,6-beta-D-fructan 6-levanbiohydrolase (LF2ase) (EC 3.2.1.64) that converts levan into levanbiose was cloned from the genomic DNA of Streptomyces exfoliatus F3-2. The gene encoded a signal peptide of 37 amino acids and a mature protein of 482 amino acids with a total length of 1560 bp and was successfully expressed in Escherichia coli. The similarities of primary structure were observed with levanases from Clostridium acetobutylicum, Bacillus subtilis, B. stearothermophilus (51.0-54.3%) and with LF2ase from Microbacterium levaniformans (53.9%). The enzyme from S. exfoliatus F3-2 shared the conserved six domains and the completely conserved five amino acid residues with family 32 glycosyl hydrolases, which include levanase, inulinase, and invertase. These observations led to the conclusion that the enzyme belongs to family 32 glycosyl hydrolases.

Amino Acid Sequence↗
PubMed1994

Comparative enzyme histochemistry of the early and term rat decidua with special attention to decidual regression.

As the early rat decidua is believed to fulfil functions other than the late or basal decidua, the question as to whether this difference is reflected in decidual cell metabolism was investigated. Using cryosections of pregnant rat uteri of the 10th, 15th and 21st gestational day, activities of oxyradical-forming enzymes and hydrolases were analysed histochemically. The enzyme activities of decidual stromal cells and fibroblasts of the metrial gland exhibited three main fluctuations. One group of enzyme activities did not change during gestation, a second group decreased or disappeared, and a third group increased or was expressed in the late decidua only. Enzymes of the purine and polyamine pathway, including oxyradical-forming oxidases, were absent from early mesometrial decidual cells, but were highly active in the late regressing decidua and metrial gland. Some acid hydrolases and neutral proteases became active in the mature decidua. The possibility that purine-degrading and oxyradical-forming enzymes support decidual as well as metrial gland regression, and thus placental separation, by direct tissue damage and/or by indirect rupture of lysosomal membranes, inducing the release of acid hydrolases, is considered.

Animals↗
PubMed1999

Conserved sequence motifs in levansucrases and bifunctional beta-xylosidases and alpha-L-arabinases.

Comparison of the amino acid sequences of two families of glycosyl hydrolases reveals that they are related in a region in the central part of the sequences. One of these families (GH family 68) includes levansucrases and the other one (glycosyl hydrolase family 43) includes bifunctional beta-xylosidases and alpha-L-arabinofuranosidases. The similarity of the primary structure of proteins from these families allows us to consider the invariant glutamate residue as a component of their active center. It is shown for the first time that glycosyl hydrolases recognizing different glycofuranoside residues can have a common sequence motif.

Amino Acid Sequence↗
PubMed1977

Enzymes synthesizing and hydrolyzing murein in Escherichia coli. Topographical distribution over the cell envelope.

Envelopes from regions of the cell which in vivo show very little, if any, murein synthesis were isolated using the minicell-producing strain P678-54. Envelopes from minicells, representing in fact cell ends, were able to synthesize murein and to carry out transpeptidation in vitro; also all four murein hydrolase activities tested, carboxypeptidase, endopeptidase, amidase and transglycosylase, were found to be present. The specific activities of the murein synthesizing and degrading enzymes in envelopes derived from cell poles and from actively growing cells were similar. The topological distribution of murein-synthesizing enzymes and of murein hydrolases over the cell envelope is discussed.

Amidohydrolases↗
PubMed2000

Identification of the cellulose-binding domain of Fibrobacter succinogenes endoglucanase F.

The cellulose-binding domain (CBD) of Fibrobacter succinogenes endoglucanase F (EGF) has been determined. The gene encoding EGF (celF) and its derivatives were expressed in Escherichia coli. We were able to obtain eight recombinant proteins and examine their cellulose-binding ability and endoglucanase activity. Because four recombinant proteins, which contain the first N-terminal reiterated region of EGF, bound to cellulose, the region has been identified as the CBD. Although the CBD did not show significant sequence similarity with any other CBDs, it did show significant similarity with a part of endoglucanase J (CelJ) of Clostridium thermocellum F1. Moreover, a large part of the C-terminal catalytic region of EGF showed sequence similarity with alpha-L-arabinofuranosidases of glycosyl hydrolase family 51.

Amino Acid Sequence↗
PubMed1979

Regulation and function of sucrose 6-phosphate hydrolase in Streptococcus mutans.

Sucrose catabolism by Streptococcus mutans is initiated by a phosphoenolpyruvate-dependent sucrose phosphotransferase reaction that produces sucrose 6-phosphate the latter is then cleaved by a sucrose 6-phosphate hydrolase reaction that yields glucose 6-phosphate and fructose. We have examined the regulation of the sucrose 6-phosphate hydrolase and found that it was synthesized constitutively whereas sucrose phosphotransferase activity was inducible. However, the levels of both sucrose phosphotransferase and sucrose 6-phosphate hydrolase were repressed when fructose was used as a growth substrate. The specific activity of sucrose 6-phosphate hydrolase in permeabilized cells was approximately 30 mmol/min per mg (dry weight of cells), and it had an apparent Km for sucrose 6-phosphate of 0.3 mM. analysis of a mutant that was missing sucrose 6-phosphate hydrolase activity revealed that its ability to hydrolyze sucrose was reduced.

Glucosephosphates↗
PubMed1986

Isolation and characterization of the sucrose 6-phosphate hydrolase gene from Streptococcus mutans.

The Streptococcus mutans GS-5 gene, scrB, coding for sucrose 6-phosphate hydrolase activity has been cloned into Escherichia coli utilizing the bacteriophage replacement vector lambda L47.1. DNA sequences containing the gene were initially subcloned into the moderate-copy-number plasmid vector pLG339 to yield active subclones. However, due to the instability of the resultant chimeric plasmids, the gene was subsequently subcloned into the low-copy-number vector pOU61 to yield the stable hybrid plasmid pMH613. Both plasmids contain a 6.6-kilobase EcoRI fragment from strain GS-5 and express both hydrolase and sucrase activities. The relative position of the gene in the insert has been determined after Tn5 mutagenesis and deletion analysis. The cloned enzyme was purified to near homogeneity after gel filtration and anion-exchange chromatography, chromatofocusing, and preparative polyacrylamide gel electrophoresis. The purified enzyme displayed a molecular mass of 58 kilodaltons, which is significantly higher than the 48-kilodalton enzyme previously purified from S. mutans GS-5. These results suggest that processing of the hydrolase occurs in S. mutans.

Cloning, Molecular↗