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PubMed1990

The competitive inhibition of Trichoderma reesei C30 cellobiohydrolase I by guanidine hydrochloride.

The p-nitrophenylcellobiosidase (PNPCase) activity of Trichoderma reesei cellobiohydrolase I (CBH I) was competitively inhibited by concentrations of guanidine hydrochloride (Gdn HCl) that did not affect the tryptophan fluorescence of this enzyme. The Km of CBH I, 3.6 mM, was increased to 45.4 mM in the presence of 0.14 M Gdn HCl, the concentration that was required to inhibit the enzyme by 50%. A similar concentration of lithium chloride and urea had little effect on the PNPCase activity of CBH I. Maximal inhibition was pH dependent, occurring in the range of pH 4.0 to 5.0, which is in the range for maximal activity. Analysis of the inhibition data indicated that 1.2 molecules of Gdn HCl combined reversibly with 1 molecule of CBH I. Other hydrolases and proteases were also inhibited by Gdn HCl. It is suggested that the inhibition of CBH I by Gdn HCl occurs as a result of the interaction between the positively charged guanidinium group of Gdn HCl and the carboxylate group of glutamic acid 126, postulated to be in the catalytic center of this enzyme.

Binding Sites↗

PubMed1990

Site-directed mutagenesis of the putative catalytic residues of Trichoderma reesei cellobiohydrolase I and endoglucanase I.

Site directed mutagenesis has been performed to test hypotheses concerning the putative active sites of Trichoderma reesei cellobiohydrolase I and endoglucanase I. It is shown that mutagenesis of the residue E126, previously proposed to be the proton donor in CBHI, did not totally inactivate the enzyme while mutagenesis of the residue E127 in the homologous enzyme EGI resulted in complete loss of activity. These results are compared with those obtained in similar studies of other glucanases and the effects on enzymatic activity of hyperglycosylation of the yeast produced cellulases are discussed.

Catalysis↗

PubMed1991

Structural and functional analysis of Trichoderma reesei endoglucanase I expressed in yeast Saccharomyces cerevisiae.

The function of the domains of Trichoderma reesei endoglucanase I (EGI) has been studied. Truncated EGI proteins were expressed from the 3'-end deleted cDNAs in the yeast Saccharomyces cerevisiae under the control of the ADC1 expression cassette. EGI protein was detected by monoclonal antibody EI-2 and EGI activity as cleared zones around growing colonies on agar plates containing hydroxyethylcellulose (HEC) covalently stained with Ostazin brilliant red (OBR). The results showed that the The-Ser-rich hinge region and the conserved 'tail' are not necessary for the efficient synthesis and secretion of EGI in yeast, but the intact core region is necessary for the enzymatic activity.

Blotting, Western↗

PubMed1993

Identification of an essential glutamate residue in the active site of endoglucanase III from Trichoderma reesei.

n-Propyl, n-butyl and n-pentyl beta-cellobiosides with a reactive omega-epoxide in their aglycon completely and irreversibly inactivate endoglucanase III from Trichoderma reesei. The pentyl derivative was found to be most effective. From these affinity labeling experiments evidence was found for the implication of Glu329 in the reaction mechanism. This is discussed in relation to other structural/functional data known for endoglucanase III and several other family A glycanases.

Affinity Labels↗

PubMed1994

Stereochemistry of the hydrolysis of glycosidic linkage by endo-beta-1,4-xylanases of Trichoderma reesei.

Methyl beta-D-xylotrioside was used as a non-reducing substrate to investigate the stereochemistry of hydrolysis of beta-1,4-xylopyranosidic linkage by purified endo-beta-1,4-xylanases (EC 3.2.1.8) of Trichoderma reesei, employing 1H NMR spectroscopy. The fungus produces one acidic species (pI 4.8-5.5), designated as EXI, and one alkaline species (pI 8.5-9.0), designated as EXII. Both enzymes were found to cleave the xylotrioside predominantly to methyl beta-D-xyloside and xylobiose. Monitoring of the intensity of the H-1 signals of alpha- and beta-xylobiose during the time course of hydrolysis clearly showed that both enzymes liberate the beta-anomer of xylobiose, i.e. a product with anomeric configuration identical with that of the cleaved glycosidic linkage. This means that both EXI and EXII belong to the so-called retaining glycanases that utilize the double displacement reaction mechanism of hydrolysis.

Endo-1,4-beta Xylanases↗

PubMed1995

Cre1, the carbon catabolite repressor protein from Trichoderma reesei.

In order to investigate the mechanism of carbon catabolite repression in the industrially important fungus Trichoderma reesei, degenerated PCR-primers were designed to amplify a 0.7-bp fragment of the cre1 gene, which was used to clone the entire gene. It encodes a 402-amino acid protein with a calculated M(r) of 43.6 kDa. Its aa-sequence shows 55.6% and 54.7% overall similarity to the corresponding genes of Aspergillus nidulans and A. niger, respectively. Similarity was restricted to the aa-region containing the C2H2 zinc finger and several aa-regions rich in proline and basic amino acids, which may be involved in the interaction with other proteins. Another aa-region rich in the SPXX-motif that has been considered analogous to a region of yeast RGR1p, was instead identified as a domain occurring in several eucaryotic transcription factors. The presence of the cre1 translation product was demonstrated with polyclonal antibodies against Cre1, which identified a protein of 43 (+/- 2) kDa in cell-free extracts from T. reesei. A Cre1 protein fragment from the two zinc fingers to the region similar to the aa-sequence of eucaryotic transcription factors, was expressed in Escherichia coli as a fusion protein with glutathione S-transferase. EMSA and in vitro footprinting revealed binding of the fusion protein to the sequence 5'-GCGGAG-3', which matches well with the A. nidulans consensus sequence for CreA binding (5'-SYGGRG-3'). Cell-free extracts of T. reesei formed different complexes with DNA-fragments carrying this binding sites, and the presence of Cre1 and additional proteins in these complexes was demonstrated. We conclude that T. reesei Cre1 is the functional homologue of Aspergillus CreA and that it binds to its target sequence probably as a protein complex.

Amino Acid Sequence↗

PubMed1987

Crystallization and preliminary X-ray diffraction study of a xylanase from Trichoderma harzianum.

A 20,000 Mr xylanase from Trichoderma harzianum has been purified and crystallized from 20% (w/v) saturated ammonium sulphate solutions. The unit cell is orthorhombic, space group P2(1)2(1)2(1), with unit cell lengths a = 44.2 A, b = 94.1 A, c = 51.6 A. Data from native crystals and several potential heavy-atom derivatives have been collected. An X-ray analysis to at least 2.8 A resolution appears to be feasible.

Crystallization↗

PubMed1991

Genetic engineering of Trichoderma to produce strains with novel cellulase profiles.

Genetic engineering has been used to modify the proportion of different cellulases produced by a hypercellulolytic Trichoderma reesei mutant strain. A general expression vector, pAMH110, containing the promoter and terminator sequences of the strongly expressed main cellobiohydrolase 1 (cbh1) gene was used to overexpress a cDNA coding for EGI, the major endoglucanase (1,4,beta-D-glucan glucanohydrolase, EC 3.2.1.4). An in vitro modified cbh1 cDNA, incapable of coding for active enzyme, was used to inactivate the major cellobiohydrolase (1,4-beta-D-glucan cellobiohydrolase, EC 3.2.1.91) gene. In this way, new strains producing elevated amounts of the specific endoglucanase 1 (EGI) and/or lacking the major cellobiohydrolase (CBHI) were produced, and these have been further characterized.

Base Sequence↗

PubMed1993

Rapid release of protoplasts from Eremothecium ashbyii in comparison with Trichoderma reesei and Penicillium chrysogenum using novozyme and funcelase.

Protoplast release in Eremothecium ashbyii, Trichoderma reesei, and Penicillium chrysogenum was achieved using commercially available enzymes, Novozyme 234 and Funcelase. A rapid release of protoplasts was observed in E. ashbyii, yielding nearly 4.0 x 10(7) protoplasts ml-1 in 10-35 min. The regeneration frequency of protoplasts from T. reesei, P. chrysogenum, and E. ashbyii using Funcelase was 51.77, 28.32, and 7.64%, respectively, and was higher in comparison with Novozyme-derived protoplasts.

Biotechnology↗

PubMed1993

Comparison of Ellman's reagent with N-(1-pyrenyl)maleimide for the determination of free sulfhydryl groups in reduced cellobiohydrolase I from Trichoderma reesei.

The enzyme cellobiohydrolase I (CBH I) from Trichoderma reesei was treated with 5 mM dithiothreitol at different pH values in order to reduce some or all of its 12 disulfide bridges. A discrepancy was found in the number of free sulfhydryl (SH) groups generated upon the reduction of CBH I when they were measured using N-(1-pyrenyl)maleimide (PM) or Ellman's reagent, 5,5'-dithiobis(2-nitrobenzoic acid). For example, the number of SH mol generated/mol CBH I at pH 8.5 was determined to be 16 and < 1 when measured using PM or Ellman's reagent, respectively. The low value obtained with Ellman's reagent may be due to the electrostatic repulsion between the carboxylic acid groups in CBH I and those in Ellman's reagent. The fluorimetric assay used for determining SH molecules in reduced CBH I, based on their reaction with PM, is described.

Cellulose 1,4-beta-Cellobiosidase↗

PubMed1990

The conserved terminal region of Trichoderma reesei cellulases forms a strong antigenic epitope for polyclonal antibodies.

The specificity of polyclonal antibodies (Pab) raised against Trichoderma reesei cellulases has been studied. cDNAs lacking regions coding for certain functional domains were produced by preparing series of 3'-end deletions from the cDNAs for two cellobiohydrolases, CBH I and CBH II, and an endoglucanase, EG I. The proteins coded by the full length cDNAs and the truncated proteins coded by the deleted cDNAs were expressed in yeast Saccharomyces cerevisiae, under the control of the ADC1 promoter. Each polyclonal antiserum showed cross-reactivity with other cellulases. Pabs for CBH I and CBH II both recognized EG I. Pab for EG I strongly recognized both CBH I and CBH II. By analyzing the truncated proteins, we found that these antibodies were almost entirely directed against the conserved tail of the cellulase enzymes.

Antibodies, Fungal↗

PubMed1993

Cloning of two isozymes of Trichoderma koningii glyceraldehyde-3-phosphate dehydrogenase with different sensitivity to koningic acid.

Koningic acid inhibits glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by binding to the SH group in the active center. The fungus Trichoderma koningii, the producer of koningic acid, contains two GAPDH isozymes (GAPDHs I and II). GAPDH I is inhibited 50% by 1.1.10(-3) M koningic acid, while GAPDH II is inhibited 50% at 6.8 x 10(-6) M. cDNAs of the two isozymes were cloned from T. koningii and their nucleotide sequences were determined. The sequence of coding region and codon usage in both clones were compared with each other and with those of the gene for Aspergillus nidulans GAPDH (enzyme activity is inhibited 50% by 2.7 x 10(-7) M koningic acid). Results indicated that GAPDH II is more closely related to A. nidulans GAPDH than GAPDH I. All essential amino acid residues, except 174 and 181, which are implicated in catalysis and binding of NAD and substrates, were conserved among A. nidulans GAPDH and GAPDHs I and II. Residues 174 and 181 are threonine in both A. nidulans GAPDH and GAPDH II, but alanine and serine, respectively, in GAPDH I. The side-chain of alanine-174 in GAPDH I can not replace threonine-174 functionally as threonine-174 side-chain forms a hydrogen bond with the catalytically essential histidine-176.

Amino Acid Sequence↗

PubMed1990

Comparison of the hydrolytic activity and fluorescence of native, guanidine hydrochloride-treated and renatured cellobiohydrolase I from Trichoderma reesei.

Guanidine hydrochloride (GdnHCl) is an effective agent for the elution of cellulase protein from unhydrolyzed cellulosic residues, but once eluted the enzyme is inactive. The studies described in this paper examine the effect of GdnHCl on the hydrolytic activity and tryptophan fluorescence of cellobiohydrolase I (CBH I) from Trichoderma reesei. CBH I was found to be completely inactivated by 0.25 M GdnHCl, but higher concentrations of GdnHCl were required to partially unfold this enzyme, as determined from the measurement of a decrease in its tryptophan fluorescence. Binding of CBH I to microcrystalline cellulose was prevented by 4 M GdnHCl, suggesting that a conformational change of CBH I resulted in the loss of substrate binding. Removal of the denaturant from CBH I by dialysis or gel filtration allowed the kinetics of the reactivation of CBH I, after 4 M GdnHCl treatment, to be studied. The fluorescence and specific hydrolytic activity of native and renatured CBH I were comparable. It is concluded, therefore, that GdnHCl may be used to elute cellulase components, such as CBH I, adsorbed on undigested cellulosic substrates since this component can easily be renatured and subsequently reused.

Cellulose↗

PubMed1991

A re-appraisal of multiplicity of endoglucanase I from Trichoderma reesei using monoclonal antibodies and plasma desorption mass spectrometry.

An endo beta-1,4-glucanase (EC 3.2.1.4, 1.4-(1,3;1,4)-beta-D-glucan 4 glucanhydrolase) was purified to apparent homogeneity from culture filtrates of Trichoderma reesei QM 9414. Identity of the protein with endoglucanase I (EG I) was examined by subjecting CNBr fragments of the protein to analysis by plasma desorption mass spectrometry. Seven non-glycosylated fragments, mapped on the eg1 gene sequence, could be identified, hence proving at least 39.4% identity of the amino acid sequence. No sign for microheterogeneity was observed. Purified EG I was used to prepare monoclonal antibodies. 17 stable clones were obtained, of which one--Mab EG 3--was used to analyze several commercial T. reesei cellulase preparations as well as culture filtrates from T. pseudokoningii and T. longibrachiatum for the presence of EG I. Most of them contained immunoreactive material migrating as a prominent 50-55 kDa band on SDS-PAGE, resembling EG I, but in some instances additional lower molecular weight bands were also observed. Cultivation of T. reesei at low pH led to an increase of these lower molecular weight bands. EG I was rather stable against proteolysis by papain in vitro, but after prolonged treatment, immunopositive products of 50 and 45 kDa were produced at the expense of the 55 kDa band. Our monoclonal antibodies failed to react with a low-molecular-weight endoglucanase, which was previously shown to be detectable with polyclonal antiserum against EG I. However, all monoclonals reacted with a 118 kDa protein which is most probably a dimer of EG I. These results are discussed with respect to the occurrence of multiple forms of EG I in T. reesei cellulase preparations.

Antibodies, Monoclonal↗

PubMed1992

Purification and characterization of two extracellular beta-glucosidases from Trichoderma reesei.

A major beta-glucosidase I and a minor beta-glucosidase II were purified from culture filtrates of the fungus Trichoderma reesei grown on wheat straw. The enzymes were purified using CM-Sepharose CL-6B cation-exchange and DEAE Bio-Gel A anion-exchange chromatography steps, followed by Sephadex G-75 gel filtration. The isolated enzymes were homogeneous in SDS-polyacrylamide gel electrophoresis and isoelectric focusing. beta-Glucosidase I (71 kDa) was isoelectric at pH 8.7 and contained 0.12% carbohydrate; beta-glucosidase II (114 kDa) was isoelectric at pH 4.8 and contained 9.0% carbohydrate. Both enzymes catalyzed the hydrolysis of cellobiose and p-nitrophenyl-beta-D-glucoside (pNPG). The Km and kcat/Km values for cellobiose were 2.10 mM, 2.45.10(4) s-1 M-1 (beta-glucosidase I) and 11.1 mM, 1.68.10(3) s-1 M-1 (beta-glucosidase II). With pNPG as substrate the Km and kcat/Km values were 182 microM, 7.93.10(5) s-1 M-1 (beta-glucosidase I) and 135 microM, 1.02.10(6) s-1 M-1 (beta-glucosidase II). The temperature optimum was 65-70 degrees C for beta-glucosidase I and 60 degrees C for beta-glucosidase II, the pH optimum was 4.6 and 4.0, respectively. Several inhibitors were tested for their action on both enzymes. beta-Glucosidase I and II were competitively inhibited by desoxynojirimycin, gluconolactone and glucose.

Cations, Divalent↗

PubMed1990

Biological control of Penicillium digitatum by Trichoderma viride on postharvest citrus fruits.

In previous studies it was shown that Trichoderma viride, isolated from Spanish citrus packing houses, showed antagonistic activity against Penicillium digitatum in in vitro laboratory tests. In the present in vivo studies Navelina oranges, protected with aqueous suspension of T. viride (2.5 x 10(6) to 2.5 x 10(9) spores per ml), showed an increase in resistance toward P. digitatum. Oranges, inoculated with P. digitatum, did not produce lesions after 5 days when T. viride was applied 48 h or 72 h before inoculation.

Citrus↗

PubMed1990

Pilot scale production of a heterologous Trichoderma reesei cellulase by Saccharomyces cerevisiae.

Cellobiohydrolase II of Trichoderma reesei was produced in laboratory and pilot scale using a transformant strain of Saccharomyces cerevisiae harbouring a multicopy expression plasmid. Different strategies were compared for concentration and partial purification of the enzyme produced in a 200 1 pilot cultivation. After efficient separation of biomass and sub-cellular particulate matter, a combination of ultrafiltration and adsorbent treatment for removal of protein impurities was used to provide a concentrate for chromatographic purification. Effective purification of the CBH II protein was obtained by passing the concentrate through a column of DEAE Sepharose, on which almost all the yeast proteins were adsorbed. The purified enzyme reacted with antibodies prepared against T. reesei CBH II and catalyzed partial solubilization of crystalline cellulose to soluble sugars.

Biotechnology↗

PubMed1991

Pilot scale production of a Trichoderma reesei endo-beta-glucanase by brewer's yeast.

Endo-beta-glucanase I (EGI) of Trichoderma reesei was produced in laboratory and pilot scale using recombinant strains of "bottom-fermenting" Saccharomyces cerevisiae. The gene eg/1 was integrated in the chromosome or an expression cassette was inserted on a multicopy plasmid. Expression levels were compared in a laboratory scale bioreactor. The best EGI-producing strain was cultivated in pilot scale. Adsorbent treatment was used to remove endogenous yeast proteins and other impurities from the culture filtrate during concentration. Effective pilot scale one-step purification of the EGI protein was obtained using DEAE-Sepharose, on which EGI was weakly bound. The purified enzyme reacted with antibodies prepared against T. reesei EGI and catalyzed the hydrolysis of both insoluble and soluble substrates.

Fermentation↗