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PubMed1992

Novel oligosaccharide constituents of the cellulase complex of Bacteroides cellulosolvens.

The multiple cellulase-containing protein complex, isolated from the cellulolytic bacterium Bacteroides cellulosolvens, contains oligosaccharides which are O-linked mainly to a 230-kDa subunit. The oligosaccharide chains were liberated by alkaline-borohydride treatment and fractionated as oligosaccharide alditols via gel-permeation chromatography and HPLC. The fractions were investigated by one- and two-dimensional (correlation, homonuclear Hartmann-Hahn, rotating-frame nuclear Overhauser enhancement) 500-MHz 1H-NMR spectroscopy in combination with monosaccharide and methylation analyses and with fast-atom-bombardment mass spectrometry. The following carbohydrate structures could be established: [formula: see text] The results indicate an interesting similarity between the oligosaccharide moieties of the cellulase complex of B. cellulosolvens and of Clostridium thermocellum [Gerwig, G. J., Kamerling, J. P., Vliegenthart, J. F. G., Morag (Morgenstern), E., Lamed, R. & Bayer, E. A. (1991) Eur. J. Biochem. 196, 115-122], having 3, 5 and 6 as common elements. The furanose form of a terminal alpha-D-galactose residue demonstrated an inhibitory effect on the interaction of Griffonia simplicifolia I isolectin B4 with the cellulosome-like entity of B. cellulosolvens.

Amidohydrolases↗
PubMed1993

Purification and characterization of endoglucanase C from Clostridium cellulolyticum. Catalytic comparison with endoglucanase A.

An Escherichia coli clone was constructed to overproduce endoglucanase C (CelCCC) from Clostridium cellulolyticum. This construction made it easier to isolate the enzyme but, as observed in the case of endoglucanase A (CelCCA) from the same organism, the purification led to the isolation of two forms of the cellulase differing in their molecular masses, 48 kDa and 41 kDa. N-terminal sequence analysis of both purified enzymes showed that the shorter form was probably the result of partial proteolysis near the COOH-extremity. The difference in mass indicated that the shorter protein lacks the C-terminal reiterated domains (20-24-amino-acid twice-repeated sequences). These particular domains are characteristic of clostridial cellulases acting on cellulose by the mean of cellulosomal particles. Biochemical and enzymic studies were performed on each form of CelCCC, and revealed that their temperature and pH optima were identical, but their catalytic parameters were quite different. Furthermore, the differences of enzymic behavior observed between the two forms of CelCCC are almost identical to those already noted in the case of the two forms of CelCCA. The stereoselectivity of the reaction catalysed by CelCCC and CelCCA was determined using proton NMR spectroscopy; CelCCC acts by configuration inversion, whereas CelCCA acts by configuration retention. The degradation patterns on cellodextrins (ranging from cellotriose to cellohexaose) and chromophoric cellodextrins (from p-nitrophenyl-cellobiose to p-nitrophenyl-cellopentaose) were also investigated in both forms of CelCCC and CelCCA. It emerged that the natural cellodextrins degradation patterns of CelCCC and CelCCA were very similar but the utilization of p-nitrophenyl-cellodextrins showed the existence of considerable differences between these two endoglucanases in terms of cleavage-site position and catalytic parameters. CelCCC and CelCCA were found not to act synergistically on the tested substrates.

Base Sequence↗
PubMed1992

Cellulose degradation by Clostridium thermocellum: from manure to molecular biology.

Clostridium thermocellum, a Gram-positive, thermophilic anaerobe produces a highly active cellulase system. This system, termed the cellulosome, is a complex composed of at least 14-18 different types of components organized around a large, cellulose-binding protein. Combining recombinant DNA technology and protein biochemistry has proved to be a successful approach in unravelling some important features of the system.

Amino Acid Sequence↗
PubMed1990

Subcellulosome preparation with high cellulase activity from Clostridium thermocellum.

We have prepared a much simpler cellulase preparation than that of cellulosomes from the extracellular broth of Clostridium thermocellum. This "subcellulosome" preparation from C. thermocellum was obtained by column chromatography on CM-Bio-Gel A and then on a lectin-affinity material (Jacalin). The subcellulosome preparation is a macromolecular complex, composed of six main protein subunits (molecular weight, 210,000 to 58,000) revealed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific activities of carboxymethylcellulase (CMCase) and Avicelase are 15- and 8-fold-higher, respectively, than those of crude extracellular cellulase. We could not further fractionate this preparation without denaturing it. The optimum pH and temperature of the subcellulosome preparation are 5.5 to 7.0 and 70 degrees C for CMCase and 5.5 to 7.0 and 65 degrees C for Avicelase. The subcellulosome preparation acted on various types of carboxymethyl cellulose, cellulose, and p-nitrophenyl-beta-D-cellobioside but not on p-nitrophenyl-beta-D-glucoside. Sulfhydryl reagents and N-bromosuccinimide inhibited both CMCase and Avicelase activities, whereas EDTA and o-phenanthroline inhibited Avicelase activity only.

Bacterial Proteins↗
PubMed1999

Characterization of an acetyl xylan esterase from the anaerobic fungus Orpinomyces sp. strain PC-2.

A 1,067-bp cDNA, designated axeA, coding for an acetyl xylan esterase (AxeA) was cloned from the anaerobic rumen fungus Orpinomyces sp. strain PC-2. The gene had an open reading frame of 939 bp encoding a polypeptide of 313 amino acid residues with a calculated mass of 34,845 Da. An active esterase using the original start codon of the cDNA was synthesized in Escherichia coli. Two active forms of the esterase were purified from recombinant E. coli cultures. The size difference of 8 amino acids was a result of cleavages at two different sites within the signal peptide. The enzyme released acetate from several acetylated substrates, including acetylated xylan. The activity toward acetylated xylan was tripled in the presence of recombinant xylanase A from the same fungus. Using p-nitrophenyl acetate as a substrate, the enzyme had a K(m) of 0.9 mM and a V(max) of 785 micromol min(-1) mg(-1). It had temperature and pH optima of 30 degrees C and 9.0, respectively. AxeA had 56% amino acid identity with BnaA, an acetyl xylan esterase of Neocallimastix patriciarum, but the Orpinomyces AxeA was devoid of a noncatalytic repeated peptide domain (NCRPD) found at the carboxy terminus of the Neocallimastix BnaA. The NCRPD found in many glycosyl hydrolases and esterases of anaerobic fungi has been postulated to function as a docking domain for cellulase-hemicellulase complexes, similar to the dockerin of the cellulosome of Clostridium thermocellum. The difference in domain structures indicated that the two highly similar esterases of Orpinomyces and Neocallimastix may be differently located, the former being a free enzyme and the latter being a component of a cellulase-hemicellulase complex. Sequence data indicate that AxeA and BnaA might represent a new family of hydrolases.

Acetylesterase↗
PubMed2005

Naturally occurring DNA transfer system associated with membrane vesicles in cellulolytic Ruminococcus spp. of ruminal origin.

A genetic transformation system with similarities to those reported for gram-negative bacteria was found to be associated with membrane vesicles of the ruminal cellulolytic genus Ruminococcus. Double-stranded DNA was recovered from the subcellular particulate fraction of all the cellulolytic ruminococci examined. Electron microscopy revealed that the only particles present resembled membrane vesicles. The likelihood that the DNA was associated with membrane vesicles (also known to contain cellulosomes) was further supported by the adherence of the particles associated with the subcellular DNA to cellulose powder added to culture filtrates. The particle-associated DNA comprised a population of linear molecules ranging in size from <20 kb to 49 kb (Ruminococcus sp. strain YE73) and from 23 kb to 90 kb (Ruminococcus albus AR67). Particle-associated DNA from R. albus AR67 represented DNA derived from genomic DNA of the host bacterium having an almost identical HindIII digestion pattern and an identical 16S rRNA gene. Paradoxically, particle-associated DNA was refractory to digestion with EcoRI, while the genomic DNA was susceptible to extensive digestion, suggesting that there is differential restriction modification of genomic DNA and DNA exported from the cell. Transformation using the vesicle-containing fraction of culture supernatant of Ruminococcus sp. strain YE71 was able to restore the ability to degrade crystalline cellulose to two mutants that were otherwise unable to do so. The ability was heritable and transferred to subsequent generations. It appears that membrane-associated transformation plays a role in lateral gene transfer in complex microbial ecosystems, such as the rumen.

Animals↗
PubMed1988

Purification of Clostridium thermocellum xylanase Z expressed in Escherichia coli and identification of the corresponding product in the culture medium of C. thermocellum.

An endoxylanase encoded by the xynZ gene of Clostridium thermocellum was purified from Escherichia coli harbouring a fragment of the gene cloned in pUC8. The purified enzyme showed two active bands of Mr 41,000 and 39,000, the latter one presumably derived from the former through proteolysis. The enzyme was highly active on xylan and para-nitrophenyl-beta-D-xylobioside. The major end product of xylan hydrolysis was xylobiose. With an antiserum raised against the enzyme purified from E. coli, an immunoreactive polypeptide of Mr 90,000, corresponding to the entire xynZ gene product, was detected in a culture supernatant from C. thermocellum grown on cellulose. By immunological detection, xylanase Z was shown to be associated with a cellulose-binding, high-molecular-weight fraction whose properties coincided with those described previously for the cellulose-degrading complex of C. thermocellum known as the cellulosome.

Bacterial Proteins↗
PubMed1990

Cellulase system of a free-living, mesophilic clostridium (strain C7).

The enzymatic activity responsible for crystalline cellulose degradation (Avicelase activity) by a mesophilic clostridium (strain C7) was present in culture supernatant fluid but was not detected in significant amounts in association with whole cells or in disrupted cells. Cells of the mesophilic clostridium lacked cellulosome clusters on their surface and did not adhere to cellulose fibers. The extracellular cellulase system of the mesophilic clostridium was fractionated by Sephracryl S-300 gel filtration, and the fractions were assayed for Avicelase and carboxymethylcellulase activities. The Avicelase activity coincided with an A280 peak that eluted in the 700,000-Mr region. Nondenaturing polyacrylamide gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the 700,000-Mr fractions showed that Avicelase was present as a multiprotein aggregate that lost the ability to hydrolyze crystalline cellulose when partially dissociated by sodium dodecyl sulfate treatment. Proteins resulting from the partial dissociation of the aggregate retained carboxymethylcellulase activity. An Avicelase-deficient mutant of strain C7 (strain LS), which was not capable of degrading crystalline cellulose, lacked the Avicelase-active 700,000-Mr peak. The results indicated that an extracellular 700,000-Mr multiprotein complex, consisting of at least 15 proteins, is utilized by the mesophilic clostridium for the hydrolysis of crystalline cellulose. At least six different endo-1,4-beta-glucanases may be part of the cellulase system of strain C7. Sephacryl S-300 column fractions, corresponding to an A280 peak in the 130,000-Mr region, contained carboxymethylcellulase-active proteins that may serve as precursors for the assembly of the Avicelase-active complex by the mesophilic clostridium.

Cell Membrane↗
PubMed1993

Nucleotide sequence of the celG gene of Clostridium thermocellum and characterization of its product, endoglucanase CelG.

The nucleotide sequence of the celG gene of Clostridium thermocellum, encoding endoglucanase CelG, was determined. The open reading frame extended over 1,698 bp and encoded a 566-amino-acid polypeptide (molecular weight of 63,128) similar to the C. thermocellum endoglucanase CelB (51.5% identical residues). The N terminus displayed a typical signal peptide, followed by a catalytic domain. The C terminus, which was separated from the catalytic domain by a 25-amino-acid segment rich in Pro, Thr, and Ser, contained two conserved stretches of 22 amino acids closely similar to those previously described in other cellulases from the same organism. Expression of the gene in Escherichia coli was increased by fusing the fragment coding for the catalytic domain in frame with the start of the lacZ' gene present in the vector. A low- and a high-M(r) form of the protein were purified. The two forms displayed identical enzymatic properties. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that both forms consist of a major polypeptide of M(r) 50,000 and two minor polypeptides of M(r)s 49,000 and 48,000, resulting from heterogeneous proteolytic cleavage at the C terminus. An antiserum raised against the forms purified from E. coli reacted with an immunoreactive polypeptide of M(r) 66,000, which was associated with the extracellular cellulolytic complex of C. thermocellum known as the cellulosome.

Amino Acid Sequence↗
PubMed2001

Carbon flux distribution and kinetics of cellulose fermentation in steady-state continuous cultures of Clostridium cellulolyticum on a chemically defined medium.

The metabolic characteristics of Clostridium cellulolyticum, a mesophilic cellulolytic nonruminal bacterium, were investigated and characterized kinetically for the fermentation of cellulose by using chemostat culture analysis. Since with C. cellulolyticum (i) the ATP/ADP ratio is lower than 1, (ii) the production of lactate at low specific growth rate (mu) is low, and (iii) there is a decrease of the NADH/NAD(+) ratio and q(NADH produced)/ q(NADH used) ratio as the dilution rate (D) increases in carbon-limited conditions, the chemostats used were cellulose-limited continuously fed cultures. Under all conditions, ethanol and acetate were the main end products of catabolism. There was no shift from an acetate-ethanol fermentation to a lactate-ethanol fermentation as previously observed on cellobiose as mu increased (E. Guedon, S. Payot, M. Desvaux, and H. Petitdemange, J. Bacteriol. 181:3262-3269, 1999). The acetate/ethanol ratio was always higher than 1 but decreased with D. On cellulose, glucose 6-phosphate and glucose 1-phosphate are important branch points since the longer the soluble beta-glucan uptake is, the more glucose 1-phosphate will be generated. The proportion of carbon flowing toward phosphoglucomutase remained constant (around 59.0%), while the carbon surplus was dissipated through exopolysaccharide and glycogen synthesis. The percentage of carbon metabolized via pyruvate-ferredoxin oxidoreductase decreased with D. Acetyl coenzyme A was mainly directed toward the acetate formation pathway, which represented a minimum of 27.1% of the carbon substrate. Yet the proportion of carbon directed through biosynthesis (i.e., biomass, extracellular proteins, and free amino acids) and ethanol increased with D, reaching 27.3 and 16.8%, respectively, at 0.083 h(-1). Lactate and extracellular pyruvate remained low, representing up to 1.5 and 0.2%, respectively, of the original carbon uptake. The true growth yield obtained on cellulose was higher, [50.5 g of cells (mol of hexose eq)(-1)] than on cellobiose, a soluble cellodextrin [36.2 g of cells (mol of hexose eq)(-1)]. The rate of cellulose utilization depended on the solid retention time and was first order, with a rate constant of 0.05 h(-1). Compared to cellobiose, substrate hydrolysis by cellulosome when bacteria are grown on cellulose fibers introduces an extra means for regulation of the entering carbon flow. This led to a lower mu, and so metabolism was not as distorted as previously observed with a soluble substrate. From these results, C. cellulolyticum appeared well adapted and even restricted to a cellulolytic lifestyle.

Adenosine Triphosphate↗
PubMed2001

Genome sequence and comparative analysis of the solvent-producing bacterium Clostridium acetobutylicum.

The genome sequence of the solvent-producing bacterium Clostridium acetobutylicum ATCC 824 has been determined by the shotgun approach. The genome consists of a 3.94-Mb chromosome and a 192-kb megaplasmid that contains the majority of genes responsible for solvent production. Comparison of C. acetobutylicum to Bacillus subtilis reveals significant local conservation of gene order, which has not been seen in comparisons of other genomes with similar, or, in some cases closer, phylogenetic proximity. This conservation allows the prediction of many previously undetected operons in both bacteria. However, the C. acetobutylicum genome also contains a significant number of predicted operons that are shared with distantly related bacteria and archaea but not with B. subtilis. Phylogenetic analysis is compatible with the dissemination of such operons by horizontal transfer. The enzymes of the solventogenesis pathway and of the cellulosome of C. acetobutylicum comprise a new set of metabolic capacities not previously represented in the collection of complete genomes. These enzymes show a complex pattern of evolutionary affinities, emphasizing the role of lateral gene exchange in the evolution of the unique metabolic profile of the bacterium. Many of the sporulation genes identified in B. subtilis are missing in C. acetobutylicum, which suggests major differences in the sporulation process. Thus, comparative analysis reveals both significant conservation of the genome organization and pronounced differences in many systems that reflect unique adaptive strategies of the two gram-positive bacteria.

Amino Acid Sequence↗
PubMed2003

Regulation of expression of scaffoldin-related genes in Clostridium thermocellum.

Clostridium thermocellum produces an extracellular multienzyme complex, termed the cellulosome, that allows efficient solubilization of crystalline cellulose. The complex is organized around a large noncatalytic protein subunit, termed CipA or scaffoldin, and is found either free in the supernatant or cell bound. The binding of the complex to the cell is mediated by three cell surface anchoring proteins, OlpB, Orf2p, and SdbA, that interact with the CipA scaffoldin. The transcriptional level of the olpB, orf2, sdbA, and cipA genes was determined quantitatively by RNase protection assays in batch and continuous cultures, under carbon and nitrogen limitation. The mRNA level of olpB, orf2, and cipA varied with growth rate, reaching 40 to 60 transcripts per cell under carbon limitation at a low growth rate of 0.04 h(-1) and 2 to 10 transcripts per cell at a growth rate of 0.35 h(-1) in batch culture. The mRNA level of sdbA was about three transcripts per cell and was not influenced by growth rate. Primer extension analysis revealed two major transcriptional start sites, at -81 and -50 bp, upstream of the translational start site of the cipA gene. The potential promoters exhibited homology to the known sigma factors sigma(A) and sigma(L) (sigma(54)) of Bacillus subtilis. Transcription from the sigma(L)-like promoter was found under all growth conditions, whereas transcription from the sigma(A)-like promoter was significant only under carbon limitation. The overall expression level obtained in the primer extension analysis was in good agreement with the results of the RNase-protection assays.

Bacterial Outer Membrane Proteins↗
PubMed2004

Ruminococcus albus 8 mutants defective in cellulose degradation are deficient in two processive endocellulases, Cel48A and Cel9B, both of which possess a novel modular architecture.

The cellulolytic bacterium Ruminococcus albus 8 adheres tightly to cellulose, but the molecular biology underpinning this process is not well characterized. Subtractive enrichment procedures were used to isolate mutants of R. albus 8 that are defective in adhesion to cellulose. Adhesion of the mutant strains was reduced 50% compared to that observed with the wild-type strain, and cellulose solubilization was also shown to be slower in these mutant strains, suggesting that bacterial adhesion and cellulose solubilization are inextricably linked. Two-dimensional polyacrylamide gel electrophoresis showed that all three mutants studied were impaired in the production of two high-molecular-mass, cell-bound polypeptides when they were cultured with either cellobiose or cellulose. The identities of these proteins were determined by a combination of mass spectrometry methods and genome sequence data for R. albus 8. One of the polypeptides is a family 9 glycoside hydrolase (Cel9B), and the other is a family 48 glycoside hydrolase (Cel48A). Both Cel9B and Cel48A possess a modular architecture, Cel9B possesses features characteristic of the B(2) (or theme D) group of family 9 glycoside hydrolases, and Cel48A is structurally similar to the processive endocellulases CelF and CelS from Clostridium cellulolyticum and Clostridium thermocellum, respectively. Both Cel9B and Cel48A could be recovered by cellulose affinity procedures, but neither Cel9B nor Cel48A contains a dockerin, suggesting that these polypeptides are retained on the bacterial cell surface, and recovery by cellulose affinity procedures did not involve a clostridium-like cellulosome complex. Instead, both proteins possess a single copy of a novel X module with an unknown function at the C terminus. Such X modules are also present in several other R. albus glycoside hydrolases and are phylogentically distinct from the fibronectin III-like and X modules identified so far in other cellulolytic bacteria.

Amino Acid Sequence↗
PubMed2004

Production of heterologous and chimeric scaffoldins by Clostridium acetobutylicum ATCC 824.

Clostridium acetobutylicum ATCC 824 converts sugars and various polysaccharides into acids and solvents. This bacterium, however, is unable to utilize cellulosic substrates, since it is able to secrete very small amounts of cellulosomes. To promote the utilization of crystalline cellulose, the strategy we chose aims at producing heterologous minicellulosomes, containing two different cellulases bound to a miniscaffoldin, in C. acetobutylicum. A first step toward this goal describes the production of miniCipC1, a truncated form of CipC from Clostridium cellulolyticum, and the hybrid scaffoldin Scaf 3, which bears an additional cohesin domain derived from CipA from Clostridium thermocellum. Both proteins were correctly matured and secreted in the medium, and their various domains were found to be functional.

Bacterial Proteins↗
PubMed2005

Regulation of cellulase synthesis in batch and continuous cultures of Clostridium thermocellum.

Regulation of cell-specific cellulase synthesis (expressed in milligrams of cellulase per gram [dry weight] of cells) by Clostridium thermocellum was investigated using an enzyme-linked immunosorbent assay protocol based on antibody raised against a peptide sequence from the scaffoldin protein of the cellulosome (Zhang and Lynd, Anal. Chem. 75:219-227, 2003). The cellulase synthesis in Avicel-grown batch cultures was ninefold greater than that in cellobiose-grown batch cultures. In substrate-limited continuous cultures, however, the cellulase synthesis with Avicel-grown cultures was 1.3- to 2.4-fold greater than that in cellobiose-grown cultures, depending on the dilution rate. The differences between the cellulase yields observed during carbon-limited growth on cellulose and the cellulase yields observed during carbon-limited growth on cellobiose at the same dilution rate suggest that hydrolysis products other than cellobiose affect cellulase synthesis during growth on cellulose and/or that the presence of insoluble cellulose triggers an increase in cellulase synthesis. Continuous cellobiose-grown cultures maintained either at high dilution rates or with a high feed substrate concentration exhibited decreased cellulase synthesis; there was a large (sevenfold) decrease between 0 and 0.2 g of cellobiose per liter, and there was a much more gradual further decrease for cellobiose concentrations >0.2 g/liter. Several factors suggest that cellulase synthesis in C. thermocellum is regulated by catabolite repression. These factors include: (i) substantially higher cellulase yields observed during batch growth on Avicel than during batch growth on cellobiose, (ii) a strong negative correlation between the cellobiose concentration and the cellulase yield in continuous cultures with varied dilution rates at a constant feed substrate concentration and also with varied feed substrate concentrations at a constant dilution rate, and (iii) the presence of sequences corresponding to key elements of catabolite repression systems in the C. thermocellum genome.

Carbon↗
PubMed2006

Transcriptional analysis of the cip-cel gene cluster from Clostridium cellulolyticum.

Twelve genes encoding key components of Clostridium cellulolyticum cellulosomes are clustered. Among them, the first, second, and fifth genes encode the assembly factor CipC and the two major cellulases Cel48F and Cel9E, respectively. Cellulolytic clones were selected from the noncellulolytic cipC insertional mutant trans-complemented with a cipC expression vector, in which one homologous recombination event between the 3' end of the chromosomal cipC gene and the plasmidic cipC gene has restored the cluster continuity. The absence of the enzymes encoded by the cluster in the cipC mutant was thus only due to a strong polar effect, indicating that all genes were transcriptionally linked. Two large transcripts were detected in cellulose-grown cells by Northern hybridization: a 14-kb messenger which carries the cipC-cel48F-cel8C-cel9G-cel9E coding sequences and, in a smaller amount, a 12-kb messenger which carries the genes located in the 3' part of the cluster. Four smaller transcripts were found in large amounts: a cipC-cel48F bicistronic one and three monocistronic ones, cipC, cel48F, and cel9E. The cipC-cel48F and cel48F messengers were shown to be stable. Analysis by reverse transcription-PCR suggested transcriptional linkage of all of the open reading frames. The production of a primary very large transcript covering the entire cluster was hypothesized. Primer extension analysis has identified two putative transcriptional start sites located 638/637 and 194 nucleotides upstream of the cipC translational start. The processing of the primary transcript would lead to the production of several secondary messengers displaying different stabilities, contributing to fine tuning of expression of individual genes of the operon.

Bacterial Proteins↗
PubMed2005

A mannanase, ManA, of the polycentric anaerobic fungus Orpinomyces sp. strain PC-2 has carbohydrate binding and docking modules.

The anaerobic fungus Orpinomyces sp. strain PC-2 produces a broad spectrum of glycoside hydrolases, most of which are components of a high molecular mass cellulosomal complex. Here we report about a cDNA (manA) having 1924 bp isolated from the fungus and found to encode a polypeptide of 579 amino acid residues. Analysis of the deduced sequence revealed that it had a mannanase catalytic module, a family 1 carbohydrate-binding module, and a noncatalytic docking module. The catalytic module was homologous to aerobic fungal mannanases belonging to family 5 glycoside hydrolases, but unrelated to the previously isolated mannanases (family 26) of the anaerobic fungus Piromyces. No mannanase activity could be detected in Escherichia coli harboring a manA-containing plasmid. The manA was expressed in Saccharomyces cerevisiae and ManA was secreted into the culture medium in multiple forms. The purified extracellular heterologous mannanase hydrolyzed several types of mannan but lacked activity against cellulose, chitin, or beta-glucan. The enzyme had high specific activity toward locust bean mannan and an extremely broad pH profile. It was stable for several hours at 50 degrees C, but was rapidly inactivated at 60 degrees C. The carbohydrate-binding module of the Man A produced separately in E. coli bound preferably to insoluble lignocellulosic substrates, suggesting that it might play an important role in the complex enzyme system of the fungus for lignocellulose degradation.

Aerobiosis↗
PubMed2006

Different binding specificities of S-layer homology modules from Clostridium thermocellum AncA, Slp1, and Slp2.

S-layer homology (SLH) module polypeptides were derived from Clostridium thermocellum S-layer proteins Slp1 and Slp2 and cellulosome anchoring protein AncA as rSlp1-SLH, rSlp2-SLH, and rAncA-SLH respectively. Their binding specificities were investigated using C. thermocellum cell-wall preparations. rAncA-SLH associated with native peptidoglycan-containing sacculi from C. thermocellum, including both peptidoglycan and secondary cell wall polymers (SCWP), but not to hydrofluoric acid-extracted peptidoglycan-containing sacculi (HF-EPCS) lacking SCWPs, suggesting that SCWPs are responsible for binding with SLH modules of AncA. On the other hand, rSlp1-SLH and rSlp2-SLH associated with HF-EPCS, suggesting that these polypeptides had an affinity for peptidoglycan. A binding assay using a peptidoglycan fraction prepared from Escherichia coli cells definitely confirmed that rSlp1-SLH and rSlp2-SLH specifically interacted with peptidoglycan but not with SCWP.

Amino Acid Sequence↗