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PubMed2004

Differential recognition of animal type beta4-galactosylated and alpha3-fucosylated chito-oligosaccharides by two family 18 chitinases from Trichoderma harzianum.

We report the purification of two glycosyl hydrolase family 18 chitinases, Chit33 and Chit42, from the filamentous fungus Trichoderma harzianum and characterization using a panel of different soluble chitinous substrates and inhibitors. We were particularly interested in the potential of these (alpha/beta)(8)-barrel fold enzymes to recognize beta-1,4-galactosylated and alpha-1,3-fucosylated oligosaccharides, which are animal-type saccharides of medical relevance. Three-dimensional structural models of the proteins in complex with chito-oligosaccharides were built to support the interpretation of the hydrolysis data. Our kinetic and inhibition studies are indicative of the substrate-assisted catalysis mechanism for both chitinases. Both T. harzianum chitinases are able to catalyze some transglycosylation reactions and cleave both simple chito-oligosaccharides and synthetically modified, beta-1,4-galactosylated and alpha-1,3-fucosylated chito-oligosaccharides. The cleavage data give experimental evidence that the two chitinases have differences in their substrate-binding sites, Chit42 apparently having a deeper substrate binding groove, which provides more tight binding of the substrate at subsites (-2-1-+1+2). On the other hand, some flexibility for the sugar recognition at subsites more distal from the cleavage point is allowed in both chitinases. A galactose unit can be accepted at the putative subsites -4 and -3 of Chit42, and at the subsite -4 of Chit33. Fucose units can be accepted as a branch at the putative -3 and -4 sites of Chit33 and as a branch point at -3 of Chit42. These data provide a good starting point for future protein engineering work aiming at chitinases with altered substrate-binding specificity.

Animals↗

PubMed2006

Leaf hairs influence phytopathogenic fungus infection and confer an increased resistance when expressing a Trichoderma alpha-1,3-glucanase.

The leaf surface of a very large number of plant species are covered by trichomes. Non-glandular trichomes are specialized unicellular or multicellular structures that occur in many different plant species and function in xenobiotic detoxification and protecting the plant against pest attack. By analysing the susceptibility of trichome mutants, evidence is provided that indicates the influence of leaf trichomes on foliar fungal infections in Arabidopsis thaliana, probably by facilitating the adhesion of the fungal spores/hyphae to the leaf surface. A decreased trichome number in the hairless Arabidopsis mutant gl1 enhances tolerance against the necrotrophic fungus Botrytis cinerea. By contrast, the try mutant shows an increased susceptibility to both fungal infection and accumulation. Trichome density does not influence infection by the soil-borne pathogen Rhizoctonia solani. In addition, the influence of trichomes on foliar infection is supported by targeting the high-level expression of the Trichoderma harzianum alpha-1,3-glucanase protein to the specialized cell structures. Trichome expression of this anti-fungal hydrolase shows a significant resistance to infection by the foliar pathogen Botrytis cinerea. Resistance to this fungus is not dependent on the constitutive induction of the salicylic or jasmonic defence signalling pathways, but the presence of the alpha-1,3-glucanase protein in trichomes.

Arabidopsis↗

PubMed1996

Fine substrate specificities of four exo-type cellulases produced by Aspergillus niger, Trichoderma reesei, and Irpex lacteus on (1-->3), (1-->4)-beta-D-glucans and xyloglucan.

To investigate the fine substrate specificities of four highly purified exo-type cellulases (Exo-A from Aspergillus niger, CBHI and CBHII from Trichoderma reesei, and Ex-1 from Irpex lacteus), water-soluble substrates such as barley glucan, xyloglucan from tamarind (Tamarindus indica L.), and their oligosaccharides were employed. Four exo-type cellulases immediately hydrolyzed 3-O-beta-D-cellotriosylglucose to produce cellobiose and laminaribiose. In contrast, CBHII showed no hydrolytic activity towards 3(2)-O-beta-D-cello-biosylcellobiose, which was hydrolyzed to cellobiose by the other exo-type cellulases. These cellulases hydrolyzed the internal linkages of barley glucan and lichenan in an endo-type fashion to produce cellobiose and mix-linked oligosaccharides as main products. The DP-lowering activities of the four exo-type cellulases on barley glucan were in the order of Ex-1, CBHII, Exo-A, and CBHI. Based on gel permeation chromatography analysis of the hydrolysates, Ex-1 seemed to attack the internal cellobiosyl unit adjacent to beta-1,3-glucosidic linkages in barley glucan molecule more frequently than did the other cellulases. Xyloglucan was hydrolyzed only by CBHI and CBHII, and produced hepta-, octa-, and nona-saccharides. In addition, a xyloglucan tetradecasaccharide (XG14) was split only to heptasaccharide (XG7) by CBHI and CBHII.

Aspergillus niger↗

PubMed2000

Mechanistic study of beta-xylosidase from Trichoderma koningii G-39.

The catalytic mechanism of the beta-xylosidase purified from the culture filtrate of Trichoderma koningii G-39 was investigated. By NMR spectroscopy, the stereochemistry of the enzyme catalyzing the hydrolysis of 2,4-dinitrophenyl and p-nitrophenyl-beta-D-xylosides was found unequivocally to involve retention of the anomeric configuration. Based on the k(cat) values of a series of arylxylosides with leaving group pK(a)s in the range of 4-10, an extended Bronsted plot was constructed with a slope (beta(lg)) near zero. Enzymatic hydrolysis of aryl-beta-D-xylosides in acetate buffer (pH 4.0) containing 3 or 5% methanol showed a constant product ratio (methylxyloside/xylose), indicating the presence of a common intermediate, probably the xylosyl-enzyme intermediate. In the presence of DTT, the k(cat) values of p-cyanophenyl-beta-D-xylopyranoside and p-nitrophenyl-beta-D-xylopyranoside increased greatly. A two-step mechanism involving the formation and breakdown of the xylosyl-enzyme intermediate was therefore proposed. The rate-limiting step is the breakdown of the intermediate. The secondary deuterium kinetic isotope effect (k(H)/k(D)) measured for 2,4-dinitrophenyl-beta-D-xyloside was 1.02+/-0.01, suggesting that the transition state for breakdown of the xylosyl-enzyme intermediate is S(N)2-like.

Binding, Competitive↗

PubMed1991

Isolation, characterization, and primary structure of a base non-specific and adenylic acid preferential ribonuclease with higher specific activity from Trichoderma viride.

In order to elucidate the structure-function relationship of RNases belonging to the RNase T2 family (base non-specific and adenylic acid-preferential RNase), an RNase of this family was purified from Trichoderma viride (RNase Trv) to give three closely adjacent bands with RNase activity on slab-gel electrophoresis in a yield of 20%. The three RNases gave single band with the same mobility on slab-gel electrophoresis after endoglycosidase F digestion. The enzymatic properties including base specificity of RNase Trv were very similar to those of typical T2-family RNases such as RNase T2 from Aspergillus oryzae and RNase M from A. saitoi. The specific activity of RNase Trv towards yeast RNA was about 13-fold higher than that of RNase M. The complete primary structure of RNase Trv was determined by analyses of the peptides generated by digestion of reduced and carboxymethylated RNase Trv with Staphylococcus aureus V8 protease, lysylendopeptidase and alpha-chymotrypsin. The molecular weight of the protein moiety deduced from the sequence was 25,883. The locations of 10 half-cystine residues were almost superimposable upon those of other RNases of this family. The homologies between RNase Trv and RNase T2, RNase M, and RNase Rh (Rhizopus niveus) were 124, 132, and 92 residues, respectively. The sequences around three histidine residues, His52, His109, and His114, were highly conserved in these 4 RNases.

Adenosine Monophosphate↗

PubMed1993

Chemical modification of beta-glucosidase from Trichoderma reesei QM 9414.

The inhibition of beta-glucosidase from Trichoderma reesei QM 9414 by several specific reagents was studied. Diethylpyrocarbonate (DEP) nearly abolished the enzyme activity at concentrations above 10 mM. The presence of substrate or analogs protected the enzyme against inactivation. The reaction followed pseudo-first order kinetics with a second-order rate constant of 0.02 mM-1.min-1. The pH-dependence of the inactivation showed the involvement of a group with a pK of 5.2. Difference spectra at 242 nm and the reversal of the inactivation in the presence of 1 M hydroxylamine indicated the modification of histidine residues. Statistical analysis of residual fractional activity versus the number of modified histidine residues indicated that one histidine residue is essential for catalysis. p-Hydroxymercuribenzoate completely inhibited the enzyme at concentrations of the reagent above 2 mM. Substrate or analogs protected the enzyme against inactivation. The reaction followed pseudo-first order kinetics with a second-order rate constant of 0.002 mM-1.min-1. Treatment of the modified enzyme with 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) showed that one cysteine residue was essential for activity. At pH 5.0 2-ethoxy-1-ethoxy-carbonyl-1,2-dihydroquinoline (EEDQ) inactivated the enzyme according to pseudo-first order kinetics with a second-order rate constant of 0.12 min-1. The pH-dependence of the inactivation showed the involvement of a group with a pK of 5.64, indicating the modification of a carboxyl group essential for activity.

Diethyl Pyrocarbonate↗

PubMed1975

Enzymatic studies on a cellulase system of Trichoderma viride. III. Transglycosylation properties of two cellulase components of random type.

Two highly purified cellulases [EC 3.2.1.4], II-A, and II-B, were obtained from the cellulase system of Trichoderma viride. Both cellulases split cellopentaose retaining the beta-configuration of the anomeric carbon atoms in the hydrolysis products at both pH 3.5 and 5.0. The Km values of cellulases II-A and II-B for cellotetraose were different, but their Vmax values were similar and those for cellooligosaccharides increased in parallel with chain length. Both cellulases produced predominantly cellobiose and glucose from various cellulosic substrates as well as from higher cellooligosaccharides. Cellulase II-A preferentially attacked the holoside linkage of rho-nitrophenyl beta-D-cellobioside, whereas cellulase II-B attacked mainly the aglycone linkage of this cellobioside. Both cellulases were found to catalyze the synthesis of cellotriose from rho-nitrophenyl beta-D-cellobioside by transfer of a glucosyl residue, possibly to cellobiose produced in the reaction mixture. They were also found to catalyze the rapid synthesis of cellotetraose from cellobiose, with accompanying formation of cellotriose and glucose, which seemed to be produced by secondary random hydrolysis of the cellotetraose produced. The capacity to synthesize cellotetraose from cellobiose appeared to be greater with cellulase II-B than with cellulase II-A.

Animals↗

PubMed1975

Purification and properties of an exo-cellulase component of novel type from Trichoderma miride.

An enzyme extract from Cellulase-Onozuka, a commercial product of Trichoderma viride, was fractionated by Amberlite CG-50 column chromatography into three cellulase [EC 3.2.1.4] groups, peaks I to III. A noval enzyme, which has both beta-glucosidase [EC 3.2.1.21] and exo-carboxymethyl-cellulase (exo-CMCase) properties was obtained from peak III by extensive purification throuh consecutive column chromatography. The enzyme was homogeneous on ultracentrifugation, SDS-gel and cellulose acetate film electrophoreses and molecular sieve chromatography on Bio-Gel P-150. The molecular weight of this enzyme was estimated to be 53,000. The enzyme appeared to release cellobiose residues one by one from the nonreducing end of higher cellooligosaccharides and CM-cellulose (CMC), but to release glucosyl residues from reduced cellotriose and beta-cellobioside, resembling a beta-glucosidase in this respect. Furthermore, this exo-CMCase also attacked xylan exo-wise to produce xylobiose moleculaes one by one, but it scarcely attacked insoluble cellulose, except for a cellodextrin apparently rich in amorphous structure.

Animals↗

PubMed1976

Partial proteolysis of some cellulase components from Trichoderma viride and the substrate specificity of the modified products.

An endo-cellulase component [EC 3.2.1.4] or random type, F II, was obtained from "Cellulase Onozuka," a commercial product from Trichoderma viride, and was subjected to partial proteolysiats with a protease preparation of the same fungal origin. The resulting modified cellulase was fractioned by two steps of column chromatography, and the resulting patterns, together with the substrate specificity expressed in terms of the randomness of CMC hydrolysis and the immunological properties against anti-F II-rabbit se-um, were examined. The chromatographic patterns were very similar to those of cellulase subfractions without proteolytic treatment. Moreover, the immunological response of the modified cellulases from F II was mostly positive and their randomness of CMC hydrolysis was generally lower, compared with subfractions of F II which were not subjected to proteolysis. The subfractions of Peak III, which were obtained from F II by proteolysis, showed mostly negative immunological response and higher randomness of CMC hydrolysis compared with subfractions of Peak III which were not subjected to proteolysis. Thus, some limited proteolysis of cellulase components may, at least in part, be responsible for its multiplicity in vivo.

Amino Acids↗

PubMed1976

Enzymatic studies on a cellulase system of Trichoderma viride. IV. Purification and properties of a less-random type cellulase.

A cellulase [EC 3.2.1.4] component was purified from a crude cellulase preparation of Trichoderma viride (Meicelase) by consecutive column chromatography procedures, and was designated as cellulase III. The enzyme was homogeneous on polyacrylamide gel disc electrophoresis. The molecular weight of the enzyme was estimated to be about 45,000 by gel filtration. The optimum pH and temperature of the enzyme were pH 4.5-5.0 and 50 degrees, respectively. The enzyme was stable over the range of pH 4.5-7.5 at 4 degrees for 24 hr, and retained 40% of the original carboxymethylcellulose-saccharifying activity after heating at 100 degrees for 10 min. The enzyme was completely inactivated by 1 mM Hg2+, and partially by 1 mM Ag+ and Cu2+. The enzyme was characterized as a less-random type cellulase on the basis of its action on carboxymethylcellulose. The enzyme split cellohexaose, retaining the beta-configuration of the anomeric carbon atoms in the hydrolysis products. The Km values of cellulase III for cellooligosaccharides decreased in parallel with increase of the chain length of the substrates, while Vmax values showed a tendency to increase. The enzyme produced predominantly cellobiose and glucose from various cellulosic substrates as well as from higher cellooligosaccharides. Cellulase III preferentially attacked the aglycone linkage of p-nitrophenyl beta-D-cellobioside. The enzyme was found to catalyze the rapid synthesis of cellotetraose from cellobiose (condensation action).

Carboxymethylcellulose Sodium↗

PubMed1978

Mutarotation of hydrolysis products by different types of exo-cellulases from Trichoderma viride.

Mutarotation of products from p-nitrophenyl beta-D-cellobioside and cellopentaitol by two different types of exo-cellulases from Trichoderma viride was investigated. It was found that an exo-cellulase of glucosidase type produced from the former substrate D-glucose which was mutarotated in a downward direction, while another exo-cellulase of Avicelase type produced from the latter substrate cellobiose which was mutarotated in an upward direction.

Animals↗

PubMed1984

Purification and some properties of beta-transglycosylase of Trichoderma longibrachiatum.

A beta-transglycosylase was purified to a homogeneous state from the extract of a wheat bran Koji culture of Trichoderma longibrachiatum by column chromatography. The purified enzyme showed a typical disproportionation reaction with cellopentaose as the substrate, producing a high molecular component (a water-insoluble glucan). The enzyme showed neither cellulase nor beta-glucosidase activity. The reaction was optimal at pH 6.0 and 37 degrees C. The molecular weight of the enzyme was estimated to be 11,000 by gel filtration using a TOYOPEARL HW-55F column. The amount of the glucan synthesized by the enzyme increased with prolonged incubation in a reaction with cellopentaose, and soluble cellooligosaccharides, such as cellobiose, cellotriose, cellotetraose, and cellohexaose, were also produced. No glucose was produced in the reaction even when it was carried out for a long time. The total number of molecules (cellooligosaccharides) in the reaction mixture remained at the initial substrate level during the entire reaction. The beta-transglycosylase proved to be a specific transferase showing transfer activity of glucosyl, cellobiosyl, and cellotriosyl moieties from one cellopentaose to an acceptor molecule from cellopentaose upwards with almost 100% efficiency.

Chemical Phenomena↗

PubMed2002

Engineering of multiple arginines into the Ser/Thr surface of Trichoderma reesei endo-1,4-beta-xylanase II increases the thermotolerance and shifts the pH optimum towards alkaline pH.

We studied the effects of increase in the number of surface arginines on the enzyme activity and stability of Trichoderma reesei endo-1,4-beta-xylanase II. The number of arginines was increased in two mutant series. The first set contained six arginines on different sides of the protein surface. These arginines had no significant effect on the thermostability. However, the optimal pH region became narrower. Another series of five arginines was engineered into the 'Ser/Thr surface', formed of part of the double-layered beta-sheet located on one side of the 'right-hand-like' xylanase. These mutations shifted the activity profile to the alkaline region by approximately 0.5-1.0 pH units. In addition, the arginines on the Ser/Thr surface increased the enzyme activity at high temperature, although the enzyme stability in the absence of substrate decreased significantly at 50-55 degrees C. In the presence of the substrate, the thermostability increased 4-5-fold at 60-65 degrees C. Thus, the substrate neutralized the destabilizing effect of Ser/Thr surface arginines and revealed a stabilizing effect of the same mutations. The stabilizing effect of arginines at high temperatures was seen clearly only when five arginines were introduced into the Ser/Thr surface.

Arginine↗

PubMed1996

The active site of Trichoderma reesei cellobiohydrolase II: the role of tyrosine 169.

Trichoderma reesei cellobiohydrolase II (CBHII) is an exoglucanase cleaving primarily cellobiose units from the non-reducing end of cellulose chains. The beta-1,4 glycosidic bond is cleaved by acid catalysis with an aspartic acid, D221, as the likely proton donor, and another aspartate, D175, probably ensuring its protonation and stabilizing charged reaction intermediates. The catalytic base has not yet been identified experimentally. The refined crystal structure of CBHII also shows a tyrosine residue, Y169, located close enough to the scissile bond to be involved in catalysis. The role of this residue has been studied by introducing a mutation Y169F, and analysing the kinetic and binding behavior of the mutated CBHII. The crystal structure of the mutated enzyme was determined to 2.0 A resolution showing no changes when compared with the structure of native CBHII. However, the association constants of the mutant enzyme for cellobiose and cellotriose are increased threefold and for 4-methylumbelliferyl cellobioside over 50-fold. The catalytic constants towards cellotriose and cellotetraose are four times lower for the mutant. These data suggest that Y169, on interacting with a glucose ring entering the second subsite in a narrow tunnel, helps to distort the glucose ring into a more reactive conformation. In addition, a change in the pH activity profile was observed. This indicates that Y169 may have a second role in the catalysis, namely to affect the protonation state of the active site carboxylates, D175 and D221.

Binding Sites↗

PubMed1983

Trichoderma viride peritonitis.

A patient with renal failure secondary to amyloidosis and undergoing continuous ambulatory peritoneal dialysis had fungal peritonitis due to Trichoderma viride, an organism ubiquitous in the soil. Tissue invasion by this species has not previously been reported. In vitro susceptibility of the organism suggests that such infections may respond to amphotericin B or ketoconazole although our patient died before a response to therapy could be evaluated.

Amyloidosis↗

PubMed1987

Involvement of a conidial endoglucanase and a plasma-membrane-bound beta-glucosidase in the induction of endoglucanase synthesis by cellulose in Trichoderma reesei.

The induction of endo-1,4-beta-glucanase synthesis by Trichoderma reesei QM 9414 was investigated in conidia, mycelia and protoplasts. Cellulose induced endoglucanase synthesis only in conidia, but not in glucose-grown mycelia or protoplasts. Cellooligosaccharides and sophorose induced endoglucanase synthesis in mycelia, conidia and protoplasts. Only conidia exhibited detectable basal endoglucanase levels, whereas beta-glucosidase activity was found in conidia, mycelia and protoplasts. The beta-glucosidase was inhibited in vitro by nojirimycin and glucono-delta-lactone. Addition of either of these inhibitors to the induction medium blocked de noro synthesis of endo-1,4-beta-glucanase with cellulose (conidia) or cellooligosaccharides (protoplasts and mycelia) as inducer, whereas induction by sophorose remained unaffected. The results are consistent with the assumption that basal constitutive levels of endoglucanase and beta-glucosidase are involved in the induction of cellulase synthesis by cellulose in T. reesei.

1-Deoxynojirimycin↗

PubMed1991

Hyperpolarization and intracellular acidification in Trichoderma viride as a response to illumination.

Using indirect methods based on uptake of [3H]tetraphenylphosphonium cation and [14C]benzoic acid by cells of the fungus Trichoderma viride we found that the illumination-induced transient hyperpolarization of the plasma membrane is followed immediately by a rapid temporary decrease in intracellular pH. Hyperpolarization and intracellular acidification were completely suppressed by 150 mM-KCl and by the K(+)-ionophore valinomycin. The light-induced acidification of the cytoplasm was not observed in the presence of the cytochrome respiratory chain inhibitors antimycin A and mucidin. Based on these results, we hypothesize that the hyperpolarization of the cells is the consequence of an efflux of K+ through a light-activated K(+)-channel in the plasma membrane. The loss of positive charge in the cytoplasm caused by this efflux of cations is counterbalanced by H+ originating from the light-activated mitochondrial respiratory chain.

Hydrogen-Ion Concentration↗

PubMed1993

Characterization of phosphofructokinase II and regulation of fructose 2,6-bisphosphate levels in Trichoderma reesei.

Phosphofructokinase II (PEK II) from Trichoderma reesei was partially purified (247-fold). The calculated Km values for fructose 6-phosphate and ATP were 0.7 mM and 40 microM, respectively. Upon incubation in the presence of [gamma-32P]ATP, the enzyme formed a radioactive phosphoprotein with molecular mass of 67 kDa in autoradiography analysis after SDS-PAGE. Upon incubation in the presence of ATP-Mg and the catalytic subunit of cAMP-dependent protein kinase, its activity was not modified. The same result was obtained when a cell-free extract of T. reesei was incubated with ATP-Mg and cAMP. 2,4-Dinitrophenol caused a transient rise in cAMP levels in the fungal cell. The results provide evidence that the fructose 2,6-bisphosphate level in T. reesei is independent of cAMP concentrations and not related to a cAMP-dependent mechanism, but to the availability of substrate fructose 6-phosphate.

2,4-Dinitrophenol↗