scholarly journals Mode of action of endoglucanase III from Trichoderma reesei

1993 ◽  
Vol 289 (3) ◽  
pp. 867-873 ◽  
Author(s):  
R Macarrón ◽  
C Acebal ◽  
M P Castillón ◽  
J M Domínguez ◽  
I de la Mata ◽  
...  
Keyword(s):  
New Orleans ◽  
Trichoderma Reesei ◽  
Culture Medium ◽  
Ph Dependence ◽  
Maximal Activity ◽  
Cleavage Sites ◽  
Reaction Products ◽  
Binding Model ◽  
Independent Evidence ◽  
Affinity Labelling

Endoglucanase III (EG III) was purified to homogeneity from the culture medium of Trichoderma reesei QM 9414. It has a molecular mass of 48 kDa, and an isoelectric point of 5.1. Maximal activity was observed between pH4 and 5. Celloligosaccharides and their chromophoric derivatives were used as substrates, and the reaction products were analysed by quantitative h.p.l.c. Nucleophilic competition experiments (between methanol and water) allowed unequivocal assessment of cleavage sites. EG III preferentially released cellobiose (or the corresponding glycoside) from the reducing end of the higher cellodextrins. A putative binding model containing five subsites is proposed. The pH-dependence of 4′-methylumbelliferyl beta-cellotrioside hydrolysis indicates the presence of a protonated group with a pK 5.5 in the reaction mechanism, and the possible involvement of a carboxy group is corroborated by a temperature study (delta Hion = -15.9 J/mol). This, together with independent evidence from affinity-labelling experiments [Tomme, Macarrón and Claeyssens (1991) Cellulose '91, New Orleans, Abstr. 32] and n.m.r. studies [Gebbler, Gilkes, Claeyssens, Wilson, Béguin, Wakarchuk, Kilburn, Miller, Warren and Withers (1992) J. Biol. Chem. 267, 12559-12561], favours the assumption of a lysozyme-type (retention of configuration, two essential carboxy groups) mechanism for this family A cellulase.

scholarly journals Accumulation of α-Keto Acids as Essential Components in Cyanide Assimilation by Pseudomonas fluorescens NCIMB 11764

1998 ◽  
Vol 64 (11) ◽  
pp. 4452-4459 ◽  
Author(s):  
Daniel A. Kunz ◽  
Jui-Lin Chen ◽  
Guangliang Pan
Keyword(s):  
Pseudomonas Fluorescens ◽  
Culture Fluid ◽  
Maximal Activity ◽  
Resonance Spectroscopy ◽  
Keto Acid ◽  
Growth Substrate ◽  
Reaction Products ◽  
Cell Extracts ◽  
Keto Acids ◽  
Essential Components

ABSTRACT Pyruvate (Pyr) and α-ketoglutarate (αKg) accumulated when cells of Pseudomonas fluorescens NCIMB 11764 were cultivated on growth-limiting amounts of ammonia or cyanide and were shown to be responsible for the nonenzymatic removal of cyanide from culture fluids as previously reported (J.-L. Chen and D. A. Kunz, FEMS Microbiol. Lett. 156:61–67, 1997). The accumulation of keto acids in the medium paralleled the increase in cyanide-removing activity, with maximal activity (760 μmol of cyanide removed min−1 ml of culture fluid−1) being recovered after 72 h of cultivation, at which time the keto acid concentration was 23 mM. The reaction products that formed between the biologically formed keto acids and cyanide were unambiguously identified as the corresponding cyanohydrins by 13C nuclear magnetic resonance spectroscopy. Both the Pyr and α-Kg cyanohydrins were further metabolized by cell extracts and served also as nitrogenous growth substrates. Radiotracer experiments showed that CO2 (and NH3) were formed as enzymatic conversion products, with the keto acid being regenerated as a coproduct. Evidence that the enzyme responsible for cyanohydrin conversion is cyanide oxygenase, which was shown previously to be required for cyanide utilization, is based on results showing that (i) conversion occurred only when extracts were induced for the enzyme, (ii) conversion was oxygen and reduced-pyridine nucleotide dependent, and (iii) a mutant strain defective in the enzyme was unable to grow when it was provided with the cyanohydrins as a growth substrate. Pyr and αKg were further shown to protect cells from cyanide poisoning, and excretion of the two was directly linked to utilization of cyanide as a growth substrate. The results provide the basis for a new mechanism of cyanide detoxification and assimilation in which keto acids play an essential role.

Chemical mechanism of β-xylosidase from Trichoderma reesei QM 9414: pH-dependence of kinetic parameters

Biochimie ◽  
2001 ◽  
Vol 83 (10) ◽  
pp. 961-967 ◽  
Author(s):  
María Gómez ◽  
Pablo Isorna ◽  
Marta Rojo ◽  
Pilar Estrada
Keyword(s):  
Kinetic Parameters ◽  
Trichoderma Reesei ◽  
Ph Dependence ◽  
Chemical Mechanism

scholarly journals Ribonuclease "XlaI," an activity from Xenopus laevis oocytes that excises intervening sequences from yeast transfer ribonucleic acid precursors.

1981 ◽  
Vol 1 (3) ◽  
pp. 269-280 ◽  
Author(s):  
A Otsuka ◽  
A de Paolis ◽  
G P Tocchini-Valentini
Keyword(s):  
Xenopus Laevis ◽  
Ribonucleic Acid ◽  
Rnase A ◽  
Xenopus Laevis Oocytes ◽  
Cleavage Sites ◽  
Reaction Products ◽  
Yeast Trna ◽  
Intervening Sequences ◽  
Nuclear Extracts ◽  
Hydroxyl Termini

A ribonuclease (RNase) activity, RNase "XlaI," responsible for the excision of intervening sequences from two yeast transfer ribonucleic acid (tRNA) precursors, pre-tRNA(Tyr) and pre-tRNA(3Leu), has been purified 54-fold from nuclear extracts of Xenopus laevis oocytes. The RNase preparation is essentially free of contaminating RNase. A quantitative assay for RNase XlaI was developed, and the reaction products were characterized. RNase XlaI cleavage sites in the yeast tRNA precursors were identical to those made by yeast extracts (including 3'-phosphate and 5'-hydroxyl termini). Cleavage of pre-tRNA(3Leu) by RNase XlaI and subsequent ligation of the half-tRNA molecules do not require removal of the 5' leader or 3' trailer sequences.

scholarly journals The nucleotide sequences recognized by endonucleases AvaI and AvaII from Anabaena variabilis

1980 ◽  
Vol 185 (1) ◽  
pp. 65-75 ◽  
Author(s):  
S G Hughes ◽  
K Murray
Keyword(s):  
Nearest Neighbor ◽  
Bacteriophage Lambda ◽  
Nucleotide Sequences ◽  
Anabaena Variabilis ◽  
Cleavage Sites ◽  
Independent Evidence ◽  
Nearest Neighbor Analysis ◽  
The Individual ◽  
Lambda Dna

Determination of the 5'-terminal sequences flanking all the individual cleavage sites for endonuclease AvaI in bacteriophage-lambda DNA has shown that this enzyme recognizes the hexanucleotide sequences: (Formula: see text), This sequence is cut as shown by the arrows to give single-stranded 5'-tetranucleotide protrusions (cohesive ends). Endonucleases SmaI, XhoI and XmaI recognize different symmetrical subsets of this sequence and provide independent evidence for the occurrence of these subsets at particular endonuclease-AvaI cleavage sites in the bacteriophage-lambda genome. Further evidence for this structure came from the demonstration that DNA fragments generated by endonuclease AvaI can be ligated to form a discrete set of larger molecules and from nearest-neighbor analysis which showed that cytosine residues occurred at the 3'-side of cleavage points. The observation that endonuclease AvaII recognized a subset of the sites recognized by AsuI [Hughes, Bruce & Murray (1979) Biochem. J. 185, 59-63[led to the deduction that AvaII recognize the pentanucleotide sequence: (Formula: see text), and breaks internucleotide bonds at the positions indicated by the arrows.

scholarly journals Cloning and Characterization of a New Chitosanase From a Deep-Sea Bacterium Serratia sp. QD07

2021 ◽  
Vol 12 ◽  
Author(s):  
Qiuling Zheng ◽  
Xiangjun Meng ◽  
Mingyang Cheng ◽  
Yanfeng Li ◽  
Yuanpeng Liu ◽  
...  
Keyword(s):  
Deep Sea ◽  
Biological Activities ◽  
Maximal Activity ◽  
Industrial Applications ◽  
Potential Candidate ◽  
Reaction Products ◽  
Industrial Manufacture ◽  
Encoding Gene ◽  
Ph Range

Chitosanase is a significant chitosan-degrading enzyme involved in industrial applications, which forms chitooligosaccharides (COS) as reaction products that are known to have various biological activities. In this study, the gene csnS was cloned from a deep-sea bacterium Serratia sp. QD07, as well as over-expressed in Escherichia coli, which is a new chitosanase encoding gene. The recombinant strain was cultured in a 5 L fermenter, which yielded 324 U/mL chitosanases. After purification, CsnS is a cold-adapted enzyme with the highest activity at 60°C, showing 37.5% of the maximal activity at 0°C and 42.6% of the maximal activity at 10°C. It exhibited optimum activity at pH 5.8 and was stable at a pH range of 3.4–8.8. Additionally, CsnS exhibited an endo-type cleavage pattern and hydrolyzed chitosan polymers to yield disaccharides and trisaccharides as the primary reaction products. These results make CsnS a potential candidate for the industrial manufacture of COS.

scholarly journals Studies of the cellulolytic system of the filamentous fungus Trichoderma reesei QM 9414. Substrate specificity and transfer activity of endoglucanase I

1990 ◽  
Vol 270 (1) ◽  
pp. 251-256 ◽  
Author(s):  
M Claeyssens ◽  
H van Tilbeurgh ◽  
J P Kamerling ◽  
J Berg ◽  
M Vrsanska ◽  
...  
Keyword(s):  
Trichoderma Reesei ◽  
Filamentous Fungus ◽  
Substrate Concentration ◽  
Formation Rate ◽  
Transfer Reactions ◽  
Main Reaction ◽  
Reaction Products ◽  
Transfer Product ◽  
Endoglucanase I ◽  
Glucose Formation

Endoglucanase I from the filamentous fungus Trichoderma reesei catalyses hydrolysis and glycosyl-transfer reactions of cello-oligosaccharides. Initial bond-cleaving frequencies determined with 1-3H-labelled cello-oligosaccharides proved to be substrate-concentration-dependent. Using chromophoric glycosides and analysing the reaction products by h.p.l.c., kinetic data are obtained and, as typical for an endo-type depolymerase, apparent hydrolytic parameters (kcat., kcat./Km) increase steadily as a function of the number of glucose residues. At high substrate concentrations, and for both free cellodextrins and their aromatic glycosides, complex patterns (transfer reactions) are, however, evident. In contrast with the corresponding lactosides and 1-thiocellobiosides, and in conflict with the expected specificity, aromatic 1-O-beta-cellobiosides are apparently hydrolysed at both scissile bonds, yielding the glucoside as one of the main reaction products. Its formation rate is clearly non-hyperbolically related to the substrate concentration and, since the rate of D-glucose formation is substantially lower, strong indications for dismutation reactions (self-transfer) are again obtained. Evidence for transfer reactions catalysed by endoglucanase I further results from experiments using different acceptor and donor substrates. A main transfer product accumulating in a digest containing a chromophoric 1-thioxyloside was isolated and its structure elucidated by proton n.m.r. spectrometry (500 MHz). The beta 1-4 configuration of the newly formed bond was proved.

Ozonation of Aromatic Compounds pH-Dependence

1982 ◽  
Vol 14 (8) ◽  
pp. 849-861 ◽  
Author(s):  
E Gilbert
Keyword(s):  
Aqueous Solution ◽  
Aromatic Compounds ◽  
Ph Value ◽  
Ph Dependence ◽  
Oxidation Products ◽  
Reaction Products ◽  
Initial Compound ◽  
Ozone Absorption ◽  
Toluenesulfonic Acid ◽  
Acid Range

The ozonation of 2-nitro-p-cresol and p-toluenesulfonic acid (c = 1 mmole/l, ozone dose 10 mg O3/min l) in aqueous solution as a function of the pH-value (pH = 2,5 - 10,5) was investigated. At pH = 2,5 the reaction products of 2-nitro-p-cresol are measured quantitatively over the run of the reaction. The results show that the elimination rates for the initial compounds and the mineralization of the heterogroups increase with the pH value. On account of this result the spectrum of oxidation products is different after 90 % elimination of the initial compound as a function of pH. The values of DOC-and COD-elimination increase with increasing pH-value. Although the ozone absorption is better in the basic range one finds that 1,6 - 2,2 mg O3/mg ∆ COD are required in the basic range (pH 10), but only 1,1 mg O3/mg ∆3 COD in the acid range (pH 3).

Stability of the Magnesium Carbonate Apatite/Anionic Collagen Scaffolds: Effect of the Cross-Link Concentration

2011 ◽  
Vol 493-494 ◽  
pp. 844-848 ◽  
Author(s):  
Marcia S. Sader ◽  
Gutemberg Alves ◽  
Racquel Z. LeGeros ◽  
Gloria Dulce de Almeida Soares
Keyword(s):  
Bone Tissue ◽  
Culture Medium ◽  
Type I Collagen ◽  
Type I ◽  
Carbonate Apatite ◽  
Reaction Products ◽  
Collagen Scaffolds ◽  
Freeze Dried ◽  
The Cross

Natural bone constitutes of an inorganic phase (a biological nanoapatite) and an organic phase (mostly type I collagen). The challenge is to develop a material that can regenerate lost bone tissue with degradation and resorption kinetics compatible with the new bone formation. The aim of this study was to prepare self-organized magnesium and carbonate substituted apatite/collagen scaffolds, cross-linked with glutaraldehyde (GA). Bovine tendon was submitted to alkaline treatment resulting in a negatively charged collagen surface. The scaffolds were prepared by precipitation: simultaneous dropwise addition of solution containing calcium (Ca) and magnesium (Mg) ions and collagen into a buffered solution containing carbonate and phosphate ions in reaction vessel maintained at 37 °C, pH=8. The reaction products were cross-linked with 0.125 and 0.25% (v/v) glutaraldehyde (GA) solution and freeze-dried. The samples were characterized by Fourier-transformed infrared spectroscopy (FTIR). In vitro cytotoxicity (based on three parameters assays) and scaffolds degradation in culture medium and osteoblastic cells culture were performed in the cross-linked materials. No cytotoxic effects were observed. The cross-linked samples with the lower GA concentration showed a lower stability when placed in contact with culture medium. Human osteoblasts attached on the scaffolds surface cross-linked with 0.25% GA, forming a continuous layer after 14 days of incubation. These results showed potential application of the designed scaffolds for bone tissue engineering.

scholarly journals Inhibitory Effect of Maillard Reaction Products on Growth of the Aerobic Marine Hyperthermophilic Archaeon Aeropyrum pernix

2003 ◽  
Vol 69 (7) ◽  
pp. 4325-4328 ◽  
Author(s):  
Kee Woung Kim ◽  
Sun Bok Lee
Keyword(s):  
Maillard Reaction ◽  
Culture Medium ◽  
Reducing Sugars ◽  
Inhibitory Effect ◽  
Maillard Reaction Products ◽  
Reaction Products ◽  
Hyperthermophilic Archaeon ◽  
Browning Reaction ◽  
Aeropyrum Pernix ◽  
Maillard Browning

ABSTRACT It was found that the growth of Aeropyrum pernix was severely inhibited in a medium containing reducing sugars and tryptone due to the formation of Maillard reaction products. The rate of the Maillard browning reaction was markedly enhanced under aerobic conditions, and the addition of Maillard reaction products to the culture medium caused fatal growth inhibition.

Extracellular hemolytic activity in rapidly growing mycobacteria

1994 ◽  
Vol 40 (4) ◽  
pp. 318-321 ◽  
Author(s):  
Takezo Udou
Keyword(s):  
Hemolytic Activity ◽  
Mycobacterium Smegmatis ◽  
Culture Medium ◽  
Maximal Activity ◽  
Mycobacterium Fortuitum ◽  
Mycobacterium Chelonae ◽  
Rapidly Growing Mycobacteria ◽  
Factors Associated ◽  
Reference Strains

Little is known about virulence factors associated with rapidly growing mycobacteria. We evaluated 42 clinical isolates of Mycobacterium fortuitum and Mycobacterium chelonae and 4 reference strains of Mycobacterium smegmatis for the production of hemolysin (or hemolytic substance) as a possible contributor to the pathogenesis of disease caused by these organisms. All the strains tested possessed extracellular hemolytic activity that was stable after heating and proteinase treatment, and the active substance had a molecular weight less than 10 000. The activity accumulated in culture medium during the late exponential to mid stationary phase of growth. Hemolysis in vitro was relatively slow; incubation for 10 h at 35 °C was required to obtain maximal activity. Some specificity of the hemolysis with regard to red blood cells from different animals was observed.Key words: rapidly growing mycobacteria, Mycobacterium fortuitum, Mycobacterium chelonae, Mycobacterium smegmatis, hemolytic activity.

Sign in / Sign up

Export Citation Format

Share Document