Improving the Quality of Wheat Flour Bread by a Thermophilic Xylanase with Ultra Activity and Stability Reconstructed by Ancestral Sequence and Computational-Aided Analysis.

Xylanase is an essential component used to hydrolyze the xylan in wheat flour to enhance the quality of bread. Presently, cold-activated xylanase is popularly utilized to aid in the development of dough. In this study, ancestral sequence reconstruction and molecular docking of xylanase and wheat xylan were used to enhance the activity and stability of a thermophilic xylanase. The results indicated that the ancestral enzyme TmxN3 exhibited significantly improved activity and thermal stability. The Vmax increased by 2.7 times, and the catalytic efficiency (Kcat/Km) increased by 1.7 times in comparison to TmxB. After being incubated at 100 °C for 120 min, it still retained 87.3% of its activity, and the half-life in 100 °C was 330 min, while the wild type xylanase was only 55 min. This resulted in an improved shelf life of bread, while adding TmxN3 considerably enhanced its quality with excellent volume and reduced hardness, chewiness, and gumminess. The results showed that the hardness was reduced by 55.2%, the chewiness was reduced by 40.11%, and the gumminess was reduced by 53.52%. To facilitate its industrial application, we further optimized the production conditions in a 5L bioreactor, and the xylanase activity reached 1.52 × 106 U/mL culture.

The Motion Paradigm of Pre-Dock Zearalenone Hydrolase Predictions with Molecular Dynamics and the Docking Phase with Umbrella Sampling.

Zearalenone (ZEN) is one of the most prevalent estrogenic mycotoxins, is produced mainly by the Fusarium family of fungi, and poses a risk to the health of animals. Zearalenone hydrolase (ZHD) is an important enzyme capable of degrading ZEN into a non-toxic compound. Although previous research has investigated the catalytic mechanism of ZHD, information on its dynamic interaction with ZEN remains unknown. This study aimed to develop a pipeline for identifying the allosteric pathway of ZHD. Using an identity analysis, we identified hub genes whose sequences can generalize a set of sequences in a protein family. We then utilized a neural relational inference (NRI) model to identify the allosteric pathway of the protein throughout the entire molecular dynamics simulation. The production run lasted 1 microsecond, and we analyzed residues 139-222 for the allosteric pathway using the NRI model. We found that the cap domain of the protein opened up during catalysis, resembling a hemostatic tape. We used umbrella sampling to simulate the dynamic docking phase of the ligand-protein complex and found that the protein took on a square sandwich shape. Our energy analysis, using both molecular mechanics/Poisson-Boltzmann (Generalized-Born) surface area (MMPBSA) and Potential Mean Force (PMF) analysis, showed discrepancies, with scores of -8.45 kcal/mol and -1.95 kcal/mol, respectively. MMPBSA, however, obtained a similar score to that of a previous report.

Molecular and biochemical characterizations of a new cold-active and mildly alkaline ß-Mannanase from Verrucomicrobiae DG1235.

Mannanases catalyze the cleavage of ß-1,4-mannosidic linkages in mannans and have various applications in different biotechnological industries. In this study, a new ß-mannanase from Verrucomicrobiae DG1235 (ManDG1235) was biochemically characterized and its enzymatic properties were revealed. Amino acid alignment indicated that ManDG1235 belonged to glycoside hydrolase family 26 and shared a low amino acid sequence identity to reported ß-mannanases (up to 50% for CjMan26C from Cellvibrio japonicus). ManDG1235 was expressed in Escherichia coli. Purified ManDG1235 (rManDG1235) exhibited the typical properties of cold-active enzymes, including high activity at low temperature (optimal at 20 °C) and thermal instability. The maximum activity of rManDG1235 was achieved at pH 8, suggesting that it is a mildly alkaline ß-mannanase. rManDG1235 was able to hydrolyze a variety of mannan substrates and was active toward certain types of glucans. A structural model that was built by homology modeling suggested that ManDG1235 had four mannose-binding subsites which were symmetrically arranged in the active-site cleft. A long loop linking ß2 and α2 as in CjMan26C creates a steric border in the glycone region of active-site cleft which probably leads to the exo-acting feature of ManDG1235, for specifically cleaving mannobiose from the non-reducing end of the substrate.

Gene dosage and coexpression with endoplasmic reticulum secretion-associated factors improved the secretory expression of α-galactosidase.

The α-galactosidases, which can catalyze the removal of α-1,6-linked terminal galactose residues from galactooligosaccharide materials, have good potential for industrial applications. The high-level and efficient secretion of the α-galactosidases into the extracellular space has greatly simplified the downstream bioengineering process, facilitating their bioapplications. In this study, the effects of gene dosage and endoplasmic reticulum secretion-associated factors (ERSAs) on the secretory expression of an α-galactosidase gene derived from a Aspergillus oryzae strain were investigated by constructing multicopy expression cassettes and coexpressing the α-galactosidase gene with ERSAs. With the increase in the gene copy-number in the host genome, the expression of GalA was improved. However, the secretory expression level was not linearly related to the copy number. When the number was higher than four copies, the expression level of GalA gene declined. The ERSAs factors HAC1, PDI, and Ero1 improved the secretory expression of α-galactosidase, while Hsp40 inhibited its secretion. After methanol-induced expression in a bench-top bioreactor, Pichia recombinants carrying four copies of GalA genes reached 3520 U/mL in the supernatant of the culture. We further optimized the parameters for α-galactosidase to hydrolyze two types of galactooligosaccharides: raffinose and stachyose. This study has fulfilled the scale-up production of α-galactosidase, thus facilitating its industrial applications.

Biochemical Characterization of a New ß-Agarase from Cellulophaga Algicola.

Cellulophaga algicola DSM 14237, isolated from the Eastern Antarctic coastal zone, was found to be able to hydrolyze several types of polysaccharide materials. In this study, a predicted ß-agarase (CaAga1) from C. algicola was heterologously expressed in Escherichia coli. The purified recombinant CaAga1 showed specific activities of 29.39, 20.20, 14.12, and 8.99 U/mg toward agarose, pure agar, and crude agars from Gracilaria lemaneiformis and Porphyra haitanensis, respectively. CaAga1 exhibited an optimal temperature and pH of 40 oC and 7, respectively. CaAga1 was stable over a wide pH range from 4 to 11. The recombinant enzyme showed an unusual thermostability, that is, it was stable at temperature below or equal to 40oC and around 70 oC, but was thermolabile at about 50 oC. With the agarose as the substrate, the Km and Vmax values for CaAga1 were 1.19 mg/mL and 36.21 U/mg, respectively. The reducing reagent (dithiothreitol) enhanced the activity of CaAga1 by more than one fold. In addition, CaAga1 was salt-tolerant given that it retained approximately 70% of the maximum activity in the presence of 2 M NaCl. The thin layer chromatography results indicated that CaAga1 is an endo-type ß-agarase and efficiently hydrolyzed agarose into neoagarotetraose (NA4) and neoagarohexaose (NA6). A structural model of CaAga1 in complex with neoagarooctaose (NA8) was built by homology modeling and explained the hydrolysis pattern of CaAga1.

Structure of Staphylococcal Enterotoxin N: Implications for Binding Properties to Its Cellular Proteins.

Staphylococcus aureus strains produce a unique family of immunostimulatory exotoxins termed as bacterial superantigens (SAgs), which cross-link major histocompatibility complex class II (MHC II) molecule and T-cell receptor (TCR) to stimulate large numbers of T cells at extremely low concentrations. SAgs are associated with food poisoning and toxic shock syndrome. To date, 26 genetically distinct staphylococcal SAgs have been reported. This study reports the first X-ray structure of newly characterized staphylococcal enterotoxin N (SEN). SEN possesses the classical two domain architecture that includes an N-terminal oligonucleotide-binding fold and a C-terminal ß-grasp domain. Amino acid and structure alignments revealed that several critical amino acids that are proposed to be responsible for MHC II and TCR molecule engagements are variable in SEN, suggesting that SEN may adopt a different binding mode to its cellular receptors. This work helps better understand the mechanisms of action of SAgs.

Characterization of a novel cold-active xylanase from Luteimonas species.

Biotechnological application of xylanolytic enzymes is normally hindered by their temperature-dependent catalytic property. To satisfy the industrial demands, xylanases that can perform catalysis under cold condition are attracting attention. In this study, the biochemical properties of a predicted xylanase (laXynA) encoded in the genome of marine bacterium Luteimonas abyssi XH031T were characterized. Structure modeling and structure-based sequence alignment indicated that laXynA belongs to the glycoside hydrolase family 10, and it is 20-26% identical to other characterized cold-active xylanases in the same family. Recombinant laXynA was successfully produced in Escherichia coli system by autoinduction and purified by Ni-affinity chromatography. The isolated enzyme showed an optimum temperature of 30 °C toward beechwood xylan and retained important percentage of optimal activity at low temperatures (64, 55, and 29% at 10, 5, and 0 °C, respectively). A remarkable characteristic of laXynA was extreme halophilicity as demonstrated by fourfold enhancement on xylanase activity at 0.5 M NaCl and by maintaining nearly 100% activity at 4 M NaCl. Thin layer chromatography analysis demonstrated that laXynA is an endo xylanase. This study is the first to report the over-expression and characterization of a cold-active xylanase from Luteimonas species. The enzymatic property revealed the cold-active nature of laXynA. The enzyme is a promising candidate in saline food processing application.

Production and Functional Characterization of a Novel Mannanase from Alteromonadaceae Bacterium Bs31.

BACKGROUND: Mannans are the main components of hemicellulose in nature and serve as the major storage polysaccharide in legume seeds. To mine new mannanase genes and identify their functional characteristics are an important basis for mannan biotechnological applications. OBJECTIVE: In this study, a putative mannanase gene (ManBs31) from the genome of the marine bacterium Alteromonadaceae Bs31 was characterized. METHODS: Amino acid sequence analysis and protein structural modeling were used to reveal the molecular features of ManBs31. The catalytic domain of ManBs31 was recombinantly produced using Escherichia coli and Pichia pastoris expression systems. The biochemical properties of the enzymes were determined by reducing sugar assay and thin-layer chromatography. RESULTS: Sequence analysis revealed that ManBs31 was a multidomain protein, consisting of a catalytic domain belonging to glycoside hydrolase family 5 (GH5) and two cellulose-binding domains. Recombinant ManBs31-GH5 exhibited the maximum hydrolytic performance at 70 ºC and pH 6. It showed the best hydrolysis capacity toward konjac glucomannan (specific enzyme activity up to 1070.84 U/mg) and poor hydrolysis ability toward galactomannan with high side-chain modifications (with a specific activity of 344.97 U/mg and 93.84 U/mg to locust bean gum and ivory nut mannan, respectively). The hydrolysis products of ManBs31-GH5 were mannooligosaccharides, and no monosaccharide was generated. Structural analysis suggested that ManBs31-GH5 had a noncanonical +2 subsite compared with other GH5 mannanases. CONCLUSION: ManBs31 was a novel thermophilic endo-mannanase and it provided a new alternative for the biodegradation of mannans, especially for preparation of probiotic mannooligosaccharides.

Molecular cloning and characterization of a novel xylanase from Microbacterium imperiale YD-01.

Xylaneses are very common xylanolytic enzymes, which are widely used in food, papermaking, and other industries. In this study, a xylanase-encoding gene xyn1923, which encodes a protein of 1352 amino acids, was identified through the whole genome analysis of Microbacterium imperiale YD-01. Bioinformatics analysis showed that Xyn1923 only had maximum similarity of 37% with the reported xylanase from Alkalihalobacillus halodurans C-125, indicating that Xyn1923 was a novel xylanase. The enzymatic properties of Xyn1923 were systematically analyzed after purification. The results showed that the specific activity of the enzyme was 10.582 ± 0.413 U/mg, while the optimum pH and temperature of the enzyme were 7.0 and 70°C, respectively. The enzyme is stable in the pH range of 6.0-9.0, and the enzyme activity could maintain more than 85% of the original activity after 16 hr incubation at pH 9.0. The enzyme activity is relatively stable in the range of 30-60°C, and its enzyme activity could maintain more than 89% of the original activity after treatment at 60°C for 30 min. Low concentrations (≤1 mM) of Co2+ , Ba2+ , Fe2+ , and Fe3+ metal ions exerted a stimulatory effect on the activity of Xyn1923. And in contrast, high concentrations (≥2 mM) of the above metal ions inhibit the activity of Xyn1923. Mg2+ , Ag+ , Cu2+ , Ca2+ , Mn2+ , and Pb2+ ions showed a negative effect on the activity of Xyn1923. Enzyme kinetic studies showed that Km and Vmax values for xylan were 7.842 ± 0.538 mg/ml and 15.208 ± 0.822 U/mg, respectively. Xyn1923 was found to be a weakly alkaline thermophilic xylanase through an enzymatic property analysis. PRACTICAL APPLICATIONS: Xylanases are widely used in food and feed, biofuels, papermaking, and other industries. However, their use is limited by poor performance under the conditions of pH and temperature. Therefore, the discovery of xylanases with the capability of working efficiently at alkaline pH and high temperature is the priority for its industrial applications. In this study, a novel xylanase-encoding gene xyn1923 from Microbacterium imperiale YD-01 was cloned and heterologously expressed in Escherichia coli. Enzymatic properties of this novel xylanase were investigated, indicating that the robust thermal stability and alkali resistance of Xyn1923 make it a potential candidate for the food and paper industries.

Angiotensin-converting enzyme 2 (ACE2) proteins of different bat species confer variable susceptibility to SARS-CoV entry.

The discovery of SARS-like coronavirus in bats suggests that bats could be the natural reservoir of SARS-CoV. However, previous studies indicated the angiotensin-converting enzyme 2 (ACE2) protein, a known SARS-CoV receptor, from a horseshoe bat was unable to act as a functional receptor for SARS-CoV. Here, we extended our previous study to ACE2 molecules from seven additional bat species and tested their interactions with human SARS-CoV spike protein using both HIV-based pseudotype and live SARS-CoV infection assays. The results show that ACE2s of Myotis daubentoni and Rhinolophus sinicus support viral entry mediated by the SARS-CoV S protein, albeit with different efficiency in comparison to that of the human ACE2. Further, the alteration of several key residues either decreased or enhanced bat ACE2 receptor efficiency, as predicted from a structural modeling study of the different bat ACE2 molecules. These data suggest that M. daubentoni and R. sinicus are likely to be susceptible to SARS-CoV and may be candidates as the natural host of the SARS-CoV progenitor viruses. Furthermore, our current study also demonstrates that the genetic diversity of ACE2 among bats is greater than that observed among known SARS-CoV susceptible mammals, highlighting the possibility that there are many more uncharacterized bat species that can act as a reservoir of SARS-CoV or its progenitor viruses. This calls for continuation and expansion of field surveillance studies among different bat populations to eventually identify the true natural reservoir of SARS-CoV.

Improving the catalytic activity of thermostable xylanase from Thermotoga maritima via mutagenesis of non-catalytic residues at glycone subsites.

Endo-ß-1,4-xylanase from Thermotoga maritima, TmxB, is an industrially attractive enzyme due to its extreme thermostability. To improve its application value, four variants were designed on the basis of multiple sequence and three-dimensional structure alignments. Wild-type TmxB (wt-TmxB) and its mutants were produced via a Pichia pastoris expression system. Among four single-site mutants, the tyrosine substitution of a threonine residue (T74Y) at putative -3/-4 subsite led to a 1.3-fold increase in specific activity at 40 °C - 100 °C and pH 5 for 5 min, with beechwood xylan as the substrate. T74Y had an improved catalytic efficiency (kcat/Km), being 1.6 times that of wt-TmxB. Variants DY (two amino acid insertions) and N68Q displayed a slight increase (1.2 fold) and dramatic decline (1.7 fold) in catalytic efficiency, respectively. Mutant E67Y was totally inactive under all test conditions. Structural modeling and docking simulation elucidated structural insights into the molecular mechanism of activity changes for these TmxB variants. This study helps in further understanding the roles of the non-catalytic amino acids at the glycone subsites of xylanases from glycoside hydrolase family 10.

Immunogenicity difference between the SARS coronavirus and the bat SARS-like coronavirus spike (S) proteins.

SARS-like coronavirus (SL-CoV) in bats have a similar genomic organization to the human SARS-CoV. Their cognate gene products are highly conserved with the exception of the N-terminal region of the S proteins, which have only 63-64% sequence identity. The N-terminal region of coronavirus S protein is responsible for virus-receptor interaction. In this study, the immunogenicity of the SL-CoV S protein (S(SL)) was studied and compared with that of SARS-CoV (S(SARS)). DNA immunization in mice with S(SL) elicited a high titer of antibodies against HIV-pseudotyped S(SL). The sera had low cross-reactivity, but no neutralization activity, for the HIV-pseudotyped S(SARS). Studies using wild bat sera revealed that it is highly likely that the immunodominant epitopes overlap with the major neutralizing sites of the SL-CoV S protein. These results demonstrated that SL-CoV and SARS-CoV shared only a limited number of immunogenic epitopes in their S proteins and the major neutralization epitopes are substantially different. This work provides useful information for future development of differential serologic diagnosis and vaccines for coronaviruses with different S protein sequences.

Difference in receptor usage between severe acute respiratory syndrome (SARS) coronavirus and SARS-like coronavirus of bat origin.

Severe acute respiratory syndrome (SARS) is caused by the SARS-associated coronavirus (SARS-CoV), which uses angiotensin-converting enzyme 2 (ACE2) as its receptor for cell entry. A group of SARS-like CoVs (SL-CoVs) has been identified in horseshoe bats. SL-CoVs and SARS-CoVs share identical genome organizations and high sequence identities, with the main exception of the N terminus of the spike protein (S), known to be responsible for receptor binding in CoVs. In this study, we investigated the receptor usage of the SL-CoV S by combining a human immunodeficiency virus-based pseudovirus system with cell lines expressing the ACE2 molecules of human, civet, or horseshoe bat. In addition to full-length S of SL-CoV and SARS-CoV, a series of S chimeras was constructed by inserting different sequences of the SARS-CoV S into the SL-CoV S backbone. Several important observations were made from this study. First, the SL-CoV S was unable to use any of the three ACE2 molecules as its receptor. Second, the SARS-CoV S failed to enter cells expressing the bat ACE2. Third, the chimeric S covering the previously defined receptor-binding domain gained its ability to enter cells via human ACE2, albeit with different efficiencies for different constructs. Fourth, a minimal insert region (amino acids 310 to 518) was found to be sufficient to convert the SL-CoV S from non-ACE2 binding to human ACE2 binding, indicating that the SL-CoV S is largely compatible with SARS-CoV S protein both in structure and in function. The significance of these findings in relation to virus origin, virus recombination, and host switching is discussed.

Molecular and Biochemical Characterization of a Bimodular Xylanase From Marinifilaceae Bacterium Strain SPP2.

In this study, the first xylantic enzyme from the family Marinifilaceae, XynSPP2, was identified from Marinifilaceae bacterium strain SPP2. Amino acid sequence analysis revealed that XynSPP2 is a rare Fn3-fused xylanase, consisting of a signal peptide, a fibronectin type-III domain (Fn3), and a C-terminal catalytic domain belonging to glycoside hydrolase family 10 (GH10). The catalytic domain shared 17-46% identities to those of biochemically characterized GH10 xylanases. Structural analysis revealed that the conserved asparagine and glutamine at the glycone -2/-3 subsite of GH10 xylanases are substituted by a tryptophan and a serine, respectively, in XynSPP2. Full-length XynSPP2 and its Fn3-deleted variant (XynSPP2ΔFn3) were overexpressed in Escherichia coli and purified by Ni-affinity chromatography. The optimum temperature and pH for both recombinant enzymes were 50°C and 6, respectively. The enzymes were stable under alkaline condition and at temperature lower than 50°C. With beechwood xylan as the substrate, XynSPP2 showed 2.8 times the catalytic efficiency of XynSPP2ΔFn3, indicating that the Fn3 module promotes xylanase activity. XynSPP2 was active toward xylooligosaccharides (XOSs) longer than xylotriose. Such a substrate preference can be explained by the unique -2/-3 subsite composition in the enzyme which provides new insight into subsite interaction within the GH10 family. XynSPP2 hydrolyzed beechwood xylan into small XOSs (xylotriose and xylotetraose as major products). No monosaccharide was detected by thin-layer chromatography which may be ascribed to putative transxylosylation activity of XynSPP2. Preferring long XOS substrate and lack of monosaccharide production suggest its potential in probiotic XOS manufacture.

Understanding the Positional Binding and Substrate Interaction of a Highly Thermostable GH10 Xylanase from Thermotoga maritima by Molecular Docking.

Glycoside hydrolase family 10 (GH10) xylanases are responsible for enzymatic cleavage of the internal glycosidic linkages of the xylan backbone, to generate xylooligosaccharides (XOS) and xyloses. The topologies of active-site cleft determine the substrate preferences and product profiles of xylanases. In this study, positional bindings and substrate interactions of TmxB, one of the most thermostable xylanases characterized from Thermotoga maritima to date, was investigated by docking simulations. XOS with backbone lengths of two to five (X2⁻X5) were docked into the active-site cleft of TmxB by AutoDock The modeled complex structures provided a series of snapshots of the interactions between XOS and TmxB. Changes in binding energy with the length of the XOS backbone indicated the existence of four effective subsites in TmxB. The interaction patterns at subsites -2 to +1 in TmxB were conserved among GH10 xylanases whereas those at distal aglycone subsite +2, consisting of the hydrogen bond network, was unique for TmxB. This work helps in obtaining an in-depth understanding of the substrate-binding property of TmxB and provides a basis for rational design of mutants with desired product profiles.

Characterization of a New Cyclohexylamine Oxidase From Acinetobacter sp. YT-02.

Cyclohexylamine (CHAM) is widely used in various industries, but it is harmful to human beings and the environment. Acinetobacter sp. YT-02 can degrade CHAM via cyclohexanone as an intermediate. In this study, the cyclohexylamine oxidase (CHAO) gene from Acinetobacter sp. YT-02 was cloned. Amino acid sequence alignment indicated that the cyclohexylamine oxidase (CHAOYT-02) was 48% identical to its homolog from Brevibacterium oxydans IH-35A (CHAOIH-35). The enzyme was expressed in Escherichia coli BL21 (DE3), and purified to apparent homogeneity by Ni-affinity chromatography. The purified enzyme was proposed to be a dimer of molecular mass of approximately 91 kDa. The enzyme exhibited its maximum activity at 50°C and at pH 7.0. The enzyme was thermolabile as demonstrated by loss of important percentage of its maximal activity after 30 min incubation at 50°C. Metal ions Mg2+, Co2+, and K+ had certain inhibitory effect on the enzyme activity. The kinetic parameters K m and V max were 0.25 ± 0.02 mM and 4.3 ± 0.083 µM min-1, respectively. The biochemical properties, substrate specificities, and three-dimensional structures of CHAOYT-02 and CHAOIH-35 were compared. Our results are helpful to elucidate the mechanism of microbial degradation of CHAM in the strain YT-02. In addition, CHAOYT-02, as a potential biocatalyst, is promising in controlling CHAM pollution and deracemization of chiral amines.

Protein corona of airborne nanoscale PM2.5 induces aberrant proliferation of human lung fibroblasts based on a 3D organotypic culture.

Exposure to PM2.5 has become one of the most important factors affecting public health in the world. Both clinical and research studies have suggested that PM2.5 inhalation is associated with impaired lung function. In this study, material characterization identified the existence of nanoscale particulate matter (NPM) in airborne PM2.5 samples. When coming into contact with protein-rich fluids, the NPM becomes covered by a protein layer that forms a "protein corona". Based on a 3D organotypic cell culture, the protein corona was shown to mitigate NPM cytotoxicity and further stimulate the proliferation of human lung fibroblasts (HLFs). ROS-activated alpha-smooth muscle actin (α-SMA) is considered to be one of the proliferation pathways. In this research, 3D cell cultures exhibited more tissue-like properties compared with the growth in 2D models. Animal models have been widely used in toxicological research. However, species differences make it impossible to directly translate discoveries from animals to humans. In this research, the 3D HLF model could partly simulate the biological responses of NPM-protein corona-induced aberrant HLF proliferation in the human lung. Our 3D cellular results provide auxiliary support for an animal model in research on PM2.5-induced impaired lung function, particularly in lung fibrosis.

Author Correction: Protein corona of airborne nanoscale PM2.5 induces aberrant proliferation of human lung fibroblasts based on a 3D organotypic culture.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Correction: Functional human 3D microvascular networks on a chip to study the procoagulant effects of ambient fine particulate matter.

[This corrects the article DOI: 10.1039/C7RA11357A.].

The catalytic domain of Penicillium crustosum endoglucanase EGL1 has cellulose-binding capacity and cellulolytic activity.

The cellulase-mediated degradation of cellulosic materials, which is initiated by endoglucanases by the random cleavage of the glycosidic bonds between glucose units to break long cellulose molecules into shorter ones, represents a major carbon flow in the global carbon cycle. The structure of a typical endoglucanase contains a classical (α/ß)8 barrel fold catalytic domain, a linker region and a cellulose-binding domain. In this study, we found that both the full-length enzyme and the catalytic domain of endoglucanase EGL1 cloned from Penicillium crustosum strain 601 have CMCase and FPase activity. A cellulose-binding assay using green fluorescent protein as a marker further showed that the catalytic domain could also bind the cellulose substrate. The three-dimensional structure of the catalytic domain of EGL1 revealed that this cellulose substrate-binding capacity of the catalytic domain may come from the hydrophobic core formed by aromatic amino acids distributed in or outside the (α/ß)8 barrel fold. A glycine scanning mutagenesis assay further found that the aromatic amino acids at the bottom of the barrel fold and those adjacent to the catalytic site significantly affect the cellulolytic activity and the cellulose binding affinity of the catalytic domain. Thus, it could be speculated that the aromatic amino acids in the bottom of the barrel fold might be the main contributors in the binding capacity of the catalytic domain with the cellulose substrate, and those distributed around the active sites on the top of the enzyme might participate in moving the cellulose substrate to the active site in the barrel fold or releasing the hydrolysis products.