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PubMed1993

Isolation and properties of carboxylesterases of the termite gut-associated fungus, Xylaria nigripes. K., and their identity from the host termite, Odentotermes horni. W., mid-gut carboxylesterases.

1. The termite, Odentotermes horni. W., houses three fungal species, viz. Xylaria nigripes, Termitomyces microcorpus, and Trichoderma (species not identified), in its gut. X. nigripes was found to possess higher esterase activity levels than the other two. 2. Four esterase enzymes, viz. FE-I, -II, -III and -IV, with pI values 5.1, 5.25, 5.4 and 5.6, respectively, were identified, isolated and purified to apparent homogeneity from the fungus X. nigripes, their biochemical and enzymological properties were determined, and compared with those of the previously characterized host termite mid-gut enzymes, TE-I and -II. 3. The M(r) of FE-I and -II was 85.1 kDa and those of FE-III and -IV was 87.5 kDa. However, TE-I and -II were relatively smaller (M(r) approximately 78.5 kDa). Each of the fungal enzymes, viz. FE-I to -IV, was a homodimer with subunits associated non-covalently. The subunit M(r) were 42.6 kDa for FE-I and -II, and 43.7 kDa for FE-III and -IV. On the other hand, the termite mid-gut enzymes, TE-I and -II, were also homodimeric, but the subunits were associated covalently (subunit M(r) = 40 kDa). Immunologically the fungal esterase enzymes, viz. FE-I to -IV, were different from those of the host termite mid-gut esterases, viz. TE-I and -II. 4. The substrate specificity and inhibitor sensitivity studies classify these enzymes, i.e. FE-I to -IV, as carboxylesterases (EC 3.1.1.1). Steady-state product inhibition kinetics suggested; an ordered release of products, i.e. alcohol followed by acid, and a Uni-Bi kinetic reaction mechanism. 5. The two preliminary studies, i.e. the confinement of most esterase activity to the gut-tissue free from microorganisms and starvation of termites not leading to complete loss of esterase activity in the gut of the termites, suggested that there may not be any symbiotic relationship between termite, O. horni, and its gut associated microorganisms with regard to ester metabolism. Though the enzymes from the two sources were carboxylesterases, several of their properties were different and hence, they are different entities.

Amino Acids↗

PubMed1995

Oligosaccharides derived from the xyloglucan isolated from the seeds of Hymenaea courbaril var. stilbocarpa.

On aqueous extraction, Hymenaea courbaril var. stilbocarpa, known in Brazil as jatobá, furnishes a high yield of viscous xyloglucan (45%) from its seeds. The crude polysaccharide (B1) was hydrolysed and the products, analysed as alditol acetates, were glucose, xylose, galactose and arabinose in the ratio 50:35:13:2. After further fractionation on DEAE-cellulose column (chloride form), the main fraction (70% yield, B2) was obtained. The basic structure of the xyloglucan was determined as a cellulose-type (1-->4)-linked beta-D-glucan backbone partially substituted with side chains at O6 of alpha-D-xylopyranose, some of which were themselves substituted at O2 by the units of beta-D-galactopyranose. Treatment of the xyloglucan (B2) with commercial cellulase from Trichoderma sp. yielded six oligosaccharides. These oligosaccharides were isolated by preparative paper chromatography, and their structures were determined by gas-liquid chromatography-mass spectroscopy of the derived partially O-methylated alditol acetates. These results confirm the structure proposed for jatobá seed xyloglucan.

Brazil↗

PubMed1995

An acetylglucomannan esterase of Aspergillus oryzae; purification, characterization and role in the hydrolysis of O-acetyl-galactoglucomannan.

An acetyl glucomannan esterase (AGME) was purified to electrophoretic homogeneity from the culture supernatant of Aspergillus oryzae. This new enzyme had a molecular mass of 36 kDa and an isoelectric point of 4.6. It was most active in the pH range 5.0-5.5 and was stable for 24 h at 40 degrees C at pH 5.0-6.0. The purified esterase liberated acetic acid from O-acetyl-galactoglucomannan, O-acetyl-4-O- methylglucuronoxylan and alpha-naphtyl acetate. The specific activity was 10-times higher for acetylated mannan than for acetylated xylan. The enzyme was able to act on polymeric substrate but activity was clearly enhanced by addition of mannanase from Trichoderma reesei and alpha-galactosidase from guar seeds. Presence of mannanase also increased the liberation of acetic acid in long-term hydrolysis (24 h), while the addition of alpha-galactosidase had no effect. No significant synergism between these two glycanases and the previously characterized esterase of A. oryzae (FE), which is also able to deacetylate galactoglucomannan, was observed. Even though the AGME had 8-times higher specific galactomannan deacetylating activity than the FE, the maximum amount of acetic acid liberated from the polymeric galactoglucomannan by AGME was only 80% of that of FE. Both esterases clearly enhanced the action of mannanase and alpha-galactosidase in the degradation of O-acetyl-galactoglucomannan isolated from Norway spruce.

Aspergillus oryzae↗

PubMed1996

Cloning, sequencing, and expression of the cellulase genes of Humicola grisea var. thermoidea.

We have cloned an endoglucanase (EGI) gene and a cellobiohydrolase (CBHI) gene of Humicola grisea var. thermoidea using a portion of the Trichoderma reesei endoglucanase I gene as a probe, and determined their nucleotide sequences. The deduced amino acid sequence of EGI was 435 amino acids in length and the coding region was interrupted by an intron. The EGI lacks a hinge region and a cellulose-binding domain. The deduced amino acid sequence of CBHI was identical to the H. grisea CBHI previously reported, with the exception of three amino acids. The H. grisea EGI and CBHI show 39.8% and 37.7% identity with T. reesei EGI, respectively. In addition to TATA box and CAAT motifs, putative CREA binding sites were observed in the 5' upstream regions of both genes. The cloned cellulase genes were expressed in Aspergillus oryzae and the gene products were purified. The optimal temperatures of CBHI and EGI were 60 degrees C and 55-60 degrees C, respectively. The optimal pHs of these enzymes were 5.0. CBHI and EGI had distinct substrate specificities: CBHI showed high activity toward Avicel, whereas EGI showed high activity toward carboxymethyl cellulose (CMC).

Amino Acid Sequence↗

PubMed1987

Effects of sawdust pollution on the germination of fungal spores in Lagos Lagoon.

Four fungi, Aspergillus flavus, Aspergillus giganteus, Cladosporium oxysporum a and Trichoderma aureoviride, isolated from Lagos Lagoon, were tested for spore germination in aqueous sawdust extract of different hardwood species (Khaya ivorensis, Mitragyna ciliata and Triplochiton scleroxylon). Extracts of M. ciliata were inhibitory to spore germination especially at higher concentrations. Germ tubes of spores decreased in length with increase in extract concentration for C. oxysporum and T. aureoviride, while Aspergillus species showed increase in length up to a peak at 3% sawdust extract concentration, and thereafter germ tube lengths decreased with increasing concentration. Extracts of T. scleroxylon stimulated the spores and percentage germination increased at higher extract concentrations with no significant difference in germ tube length. Similarly, K. ivorensis had a stimulatory effect on spore germination and length of germ tube, especially at higher extract concentrations. Addition of soluble exogenous carbon and nitrogen sources to sawdust extract enhanced spore germination. Apart from A. flavus, which had only 9% germination, all the spores failed to germinate in lagoon water having 21% salinity. The spores were also inhibited by in lagoon water having 21 per thousand salinity. The spores were also inhibited by various inorganic salts, i.e. CaCl(2), KH(2)PO(4), MgSO(4) and NaCl, present in Lagos Lagoon. The results suggest that sawdust pollution causes enrichment of the lagoon, thereby enhancing spore germination.

Journal Article↗

PubMed1984

Toxicological features of T-2 toxin and related trichothecenes.

Toxicological characteristics of T-2 toxin and related trichothecenes, mycotoxins produced by Fusarium, Trichoderma, Verrucaria, and others, were investigated in regard to LD50 values, dermal toxicity, hematological changes, and tumorigenicity. The LD50 values (mg/kg) of T-2 toxin in adult male mice were po 10.5, ip 5.2, sc 2.1, and iv 4.2, and those of nivalenol were ip 4.1 and iv 6.3. These data showed that the lethal toxicity of T-2 toxin and nivalenol was about 10 times higher than deoxynivalenol . Newborn and immature animals were much more susceptible than adults. Inhalation experiments with T-2 toxin revealed that 33 ppb T-2 toxin for 160-min and 140 ppb T-2 toxin for 30-min exposure were enough to cause death in mice within several days. The dermal toxicity of T-2 toxin and macrocyclic trichothecenes ( verrucarin A and roridin A) was significantly higher than the other trichothecenes, and the induction of edema and other dermal toxicities is caused by direct attack of the trichothecenes on the capillary vessels. No tumorigenicity of fusarenon-X to dermal tissues was shown in mice. Pretreatments of mice with SH-compounds, prednisolon , phenobarbital, and 3-methylcholanthrene did not change the LD50 value of T-2 toxin.

Animals↗

PubMed1995

Metabolic disposition in rats of regular and enzymatically depolymerized sodium carboxymethylcellulose.

Partially enzyme-hydrolysed sodium carboxymethylcellulose (CMC-ENZ), which holds promise as a new, functional food ingredient, is obtained from sodium carboxymethylcellulose (CMC) by enzymatic hydrolysis with a cellulase preparation from Trichoderma longibrachiatum. In the safety evaluation of CMC-ENZ, a comparative disposition study on 14C-labelled CMC and CMC-ENZ was conducted in conventionally kept rats. The 14C label was in the two C atoms of the carboxymethyl group. Two groups of four male and four female rats each were fed diets with 5% unlabelled CMC or CMC-ENZ for a 2-wk adaptation period. A single oral dose of 14C-CMC or 14C-CMC-ENZ solution was then given by gavage (500 mg/kg body weight). Respiratory CO2, urine and faeces were collected at regular intervals, and after 120 hr organs, tissues and the carcass were sampled as well. For both experimental groups, total mean recovery of 14C was 98%, about 95% of the label being excreted with the faeces, 2% or less in the urine, 1% or less with CO2 and a small fraction being retained in the body (CMC, 0.58%; CMC-ENZ, 0.75%). Tissue retention of 14C was highest in the liver of rats of both experimental groups. Only about 49 and 65% of the faecal 14C was extracted with water in the 14C-CMC and 14C-CMC-ENZ dosed rats, respectively. Gel permeation chromatography (GPC) of the dosing solutions and the faecal extracts revealed that CMC is depolymerized during intestinal passage whereas CMC-ENZ is excreted nearly unchanged. Consequently, the molecular weight distribution of the 14C-CMC and 14C-CMC-ENZ faecal excretion products was similar. It is concluded that there is no toxicologically relevant difference between the disposition of CMC and CMC-ENZ.

Administration, Oral↗

PubMed1989

Homologues of catalytic domains of Cellulomonas glucanases found in fungal and Bacillus glycosidases.

We demonstrate homology between the catalytic domains of exoglucanase (1,4-beta-D-glucan cellobiohydrolase, EC 3.2.1.91) from Cellulomonas fimi and those of endoxylanases (1,4-beta-D-xylan xylanohydrolases, EC 3.2.1.8) from Bacillus sp. strain C-125 and the fungus Cryptococcus albidus; and between the catalytic domains of endoglucanase (1,4-(1,3:1,4)-beta-D-glucan 4-glucanohydrolase, EC 3.2.1.4) from Cellulomonas fimi and exoglucanase II from Trichoderma reesei. These five enzymes apparently evolved by reshuffling of two catalytic domains and several substrate-binding domains.

Actinomycetales↗

PubMed1992

Fungal 17 beta-hydroxysteroid dehydrogenase.

Two representatives of each of different fungal taxonomic classes were tested for constitutive 17 beta-hydroxysteroid dehydrogenase (HSDH) activity and the results were positive in all cases. The enzyme was found to be regioselective for C17 of the steroid ring and 20 beta-HSDH activity was only detected in Trichoderma viride. In most cases the oxidative pathway is favoured over the reductive pathway. The possible role of this enzyme in fungi is discussed.

17-Hydroxysteroid Dehydrogenases↗

PubMed1989

Cellulase families revealed by hydrophobic cluster analysis.

The amino acid sequences of 21 beta-glycanases have been compared by hydrophobic cluster analysis. Six families of cellulases have been identified on the basis of primary structure homology: (A) endoglucanases B, C and E of Clostridium thermocellum; endoglucanases of Erwinia chrysanthemi and Bacillus sp.; endoglucanase III of Trichoderma reesei; endoglucanase I of Schizophyllum commune; (B) cellobiohydrolase II of T. reesei; endoglucanases of Cellulomonas fimi and Streptomyces sp; (C) cellobiohydrolases I of T. reesei and of Phanerochaete chrysosporium; endoglucanase I of T. reesei; (D) endoglucanase A of C. thermocellum and an endoglucanase from Ce. uda; (E) endoglucanase D of C. thermocellum and an endoglucanase from Pseudomonas fluorescens; (F) xylanases of C. thermocellum and of Cryptococcus albidus and the cellobio-hydrolase of Ce. fimi. For each family, conserved potentially catalytic residues have have been listed and previous allocations of the active-site residues are evaluated in the light of the alignment of the amino acid sequences. A strong homology is also reported for the putative cellulose-binding domains of cellulases of Ce. fimi and of P. fluorescens.

Amino Acid Sequence↗

PubMed1992

Isolation and characterization of a cellulose-growth-specific gene from Agaricus bisporus.

The edible basidiomycete, Agaricus bisporus, produces extracellular endoglucanase. Endoglucanase production is induced by cellulose and repressed by fructose in A. bisporus grown on minimal medium, and is regulated in activity during fruiting body development. An anti-endoglucanase antibody was used to isolate cellulase-related genes. Three main polypeptides of 38, 58, and 60 kDa were immunoprecipitated by the antibody from products of in vitro cell-free translation of mRNAs isolated from cellulose-grown mycelium. No cross-reaction was detected with the translated products from fructose-grown mycelium. This antibody was used to immunoscreen a lambda ZAPII-cDNA expression library made from mRNA isolated from cellulose-grown mycelium. Two cDNA cross-reacting clones, pSRc110 and pSRc200, were isolated. Clones pSRc110 and pSRc200 cross-hybridized and had the same restriction map. Clone pSRc200 hybrid selected an mRNA that on cell-free translation produced a 38-kDa polypeptide. The cDNA fragment from pSRc200 hybridized to a 1.3-kb mRNA from cellulose-grown mycelium. No hybridization was observed when using fructose-grown mycelium mRNA. Thus, the gene (cel1) expressing the 1.3-kb mRNA, is differentially regulated by the carbon source of the culture medium. The cell gene was isolated in a 8.9-kb EcoRI genomic fragment after hybridization to pSRc200. Sequences similar to those in the egl1 and cbh2 genes from Trichoderma reesi were found upstream from the ATG start codon in cel1. Nine short intervening sequences disrupt the cel1 coding sequence, and a strong bias against codons ending with G and A was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Agaricus↗

PubMed1995

The gene encoding the beta-1,4-endoglucanase (CelA) from Myxococcus xanthus: evidence for independent acquisition by horizontal transfer of binding and catalytic domains from actinomycetes.

The celA gene encoding a beta-1,4 endoglucanase (CelA) from Myxococcus xanthus has been cloned in Escherichia coli and sequenced. The C-terminal region of CelA displayed a high level of similarity with the catalytic domain of several Egl belonging to the glycosyl hydrolases family 6 (CenA from Cellulomonas fimi, CelA from Microbispora bispora, E2 from Thermonospora fusca, CasA from Streptomyces KSM9 and CelA1 from Streptomyces halstedii) and less similarity to the cellobiohydrolases of the fungi Trichoderma reesei and Agaricus bisporus. Using PCR amplification we found in another myxobacterium, Stigmatella aurantiaca, a part of a glycosyl hydrolase belonging to the same family. The N-terminal part of CelA displayed significant similarities with the cellulose-binding domain of other cellulases belonging to a rare subset of family II, such as the avicelase I from Streptomyces reticuli, both tandem repeats N1 and N2 of the cellulase CenC from Cellulomonas fimi, and the N-terminal part of the Egl E1 from Thermonospora fusca. Analyses of the multiple alignments and reconstruction of phylogenetic trees strongly suggest that both domains of CelA were acquired by independent horizontal transfers between Gram+ soil bacteria and scavenging myxobacteria followed by domain shuffling.

Actinomyces↗

PubMed1995

Cloning, characterization and functional expression of an endoglucanase-encoding gene from the phytopathogenic fungus Macrophomina phaseolina.

An endoglucanase-encoding clone (egl2) was isolated from the phytopathogenic soilborne deuteromycete fungus Macrophomina phaseolina (Mp). Clones were obtained from a cDNA library by functional expression in Escherichia coli. The egl2 clone hybridized to a 1.3-kb mRNA. Expression is induced by carboxymethylcellulose (CMC) and repressed by glucose. The deduced amino acid (aa) sequence revealed strong similarity to the egl3 from Trichoderma reesei (Tr) (72% for identical residues and 81% with conservative substitution over a span of 324 aa). The Mp egl2 lacks the cellulose-binding domain and linker region found in the Tr egl3. Different codon usage between the two fungi resulted in a much shorter span of nucleotide homology. The Egl2 protein cleaves cellodextrins with continguous beta, 1-4 linkages of four and larger, and shows activity against CMC and birchwood xylan.

Amino Acid Sequence↗

PubMed1995

Cloning and analysis of cDNA encoding an elongation factor 1 alpha from the dimorphic fungus Histoplasma capsulatum.

The cDNA encoding translation elongation factor 1 alpha (EF-1 alpha) was isolated from the dimorphic fungus, Histoplasma capsulatum (Hc), an important pathogen of man. A cDNA library was probed with the tef1 gene from the fungus Mucor racemosus. Ten independent clones were isolated, all with similar restriction patterns. The longest clone (1.96 kb) was sequenced. Southern blot analysis revealed that the Hc tef1 gene was present as a single copy. A single transcript of approx. 2300 nucleotides was found in total RNA from both the yeast and mold forms of the organism. Comparison of the deduced 460-amino-acid Hc EF-1 alpha protein to EF-1 alpha proteins from other species of fungi revealed the greatest degree of similarity to proteins from the filamentous ascomycetes Podospora anserina and Trichoderma reesei. Phylogenetic tree analysis of fungal tef genes indicated that Hc is most closely related to filamentous ascomycetes and most distantly related to the budding yeast Saccharomyces cerevisiae.

Amino Acid Sequence↗

PubMed1995

The cellulase complex of Neurospora crassa: cbh-1 cloning, sequencing and homologies.

We describe the isolation, cloning and sequencing of the cellobiohydrolase 1 (EC 3.2.1.91)-encoding gene (cbh-1) of Neurospora crassa. The nucleotide and amino-acid sequences have high homology with the cbh-1 of Trichoderma reesei, Humicola grisea and Phanerochaete chrysosporium, with clear signal, catalytic, hinge and substrate-binding domains in that order.

Amino Acid Sequence↗

PubMed1995

Isolation and characterization of two chitinase-encoding genes (cts1, cts2) from the fungus Coccidioides immitis.

Two chitinase (CTS)-encoding genes (cts) from Coccidioides immitis (Ci), a respiratory fungal pathogen of humans, were cloned and sequenced. Both the genomic and cDNA sequences are presented. The transcription start points and poly(A)-addition sites were confirmed. The cts1 gene contains five introns and a 1281-bp ORF which translates a 427-amino-acid (aa) protein of 47.4 kDa. The cts2 gene contains two introns and a 2580-bp ORF which translates a 860-aa protein of 91.4 kDa. The deduced CTS1 protein showed highest homology to the Aphanocladium album and Trichoderma harzianum CTS (74% and 76%, respectively), while CTS2 showed highest homology to the CTS of Saccharomyces cerevisiae (Sc) and Candida albicans (47% and 51%, respectively). The putative N-terminal sequence of the mature CTS1 protein also showed 89% homology to the reported N-terminal sequence of a 48-kDa complement fixation antigen (CF-Ag) of Ci which has demonstrated chitinase activity. The CF-Ag is a clinically important antigen used in serodiagnosis of this fungal disease. CTS2 showed several of the conserved features of the Sc CTS, including putative catalytic and Ser/Thr-rich domains, and a C-terminal Cys-rich region. We propose that CTS1 and CTS2 of Ci are members of two distinct classes of fungal chitinases, an observation not previously reported for a single fungus.

Amino Acid Sequence↗

PubMed1984

The enzymatic hydrolysis and fermentation of pretreated wood substrates.

Aspenwood chips were pretreated by steam explosion. The various wood fractions obtained were assayed for their ability to act as substrates for growth and cellulase production of different Trichoderma and Clostridium thermocellum species. Steam exploded aspenwood was as efficiently utilized as solka floc and correspondingly high cellulase activities were detected in the various culture filtrates. When T. harzianum E58 was grown on increasing concentrations of solka floc, highest cellulase and xylanase activities were detected at 1% substrate concentrations while high substrate concentrations (10-20%) inhibited growth and enzyme production. When the cellulosic substrates were supplemented with increasing amounts of glucose, cellulase and xylanase production were inhibited when the glucose concentration exceeded 0.1%. Highest xylanase activities were detected after growth of T. reesei C30 and T. harianum E58 on xylan and solka floc respectively. All of the steam exploded fractions were at least partially hydrolyzed by the T. harzianum E58 cellulase system. The extent of the pretreatment also influenced the ability of Zymomonas mobilis and Saccharomyces cerevisiae to ferment the liberated sugars to ethanol. About 85% of the theoretical yield of ethanol from cellulose could be obtained from the combined hydrolysis and fermentation of pretreated aspenwood.

Journal Article↗

PubMed1984

Hydrolysis of xylan and fermentation of xylose to ethanol.

The focus in the development of pulping processes has usually been exclusively on cellulose. However, hemicellulose could serve as a valuable source of hexose and pentose sugars. Consequently, it should not be destroyed in a process designed for very high cellulose fibre yields. Novel procedures developed for production of ethanol by the fermentation of pentoses as well as hexoses provide new possibilities of hemicellulose utilization. Many fungi produce extracellular hemicellulases. In the present work the production of xylanase and beta-xylosidase with strains of Aspergillus and Trichoderma was studied. The enzymes were used for the hydrolysis of xylan. Xylose was fermented to ethanol by the mold Fusarium oxysporum.

Journal Article↗

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