A Thermostable Chitinase with Chitin-Binding Activity fromPhaseolus limensis

Thermostable chitinase from Cohnella sp. A01: isolation and product optimization

Twelve bacterial strains isolated from shrimp farming ponds were screened for their growth activity on chitin as the sole carbon source. The highly chitinolytic bacterial strain was detected by qualitative cup plate assay and tentatively identified to be Cohnella sp. A01 based on 16S rDNA sequencing and by matching the key morphological, physiological, and biochemical characteristics. The cultivation of Cohnella sp. A01 in the suitable liquid medium resulted in the production of high levels of enzyme. The colloidal chitin, peptone, and K₂HPO₄ represented the best carbon, nitrogen, and phosphorus sources, respectively. Enzyme production by Cohnella sp. A01 was optimized by the Taguchi method. Our results demonstrated that inoculation amount and temperature of incubation were the most significant factors influencing chitinase production. From the tested values, the best pH/temperature was obtained at pH 5 and 70°C, with K_m and V_max values of chitinase to be 5.6mg/mL and 0.87μmol/min, respectively. Ag⁺, Co²⁺, iodoacetamide, and iodoacetic acid inhibited the enzyme activity, whereas Mn²⁺, Cu²⁺, Tweens (20 and 80), Triton X-100, and EDTA increased the same. In addition, the study of the morphological alteration of chitin treated by enzyme by SEM revealed cracks and pores on the chitin surface, indicating a potential application of this enzyme in several industries.

Characterization of a novel thermostable chitin-binding domain and its application in immobilization of a multifunctional hemicellulase

A novel thermostable chitin-binding domain (Tt-ChBD) of chitinase A1 from Thermoanaerobacterium thermosaccharolyticum DSM571 was cloned, characterized, and compared for its binding activity with another mesophilic chitin-binding domain (Bc-ChBD). Recombinant protein with Tt-ChBD exhibits stronger affinity to chitin than those with Bc-ChBD at temperatures from 65 °C to at least 75 °C, but not to other polysaccharides including xylan, chitosan, cellulose, and agarose. For repeated production of xylose from arabinoxylan-containing feedstocks, a best-characterized trifunctional chimeric enzyme Xar-L1-Xyn (XX) constructed in our previous work was attempted to be immobilized on chitin efficiently by genetically fusing Tt-ChBD to the N-terminal region of XX (named CXX) and the C-terminal region of XX (named XXC), respectively. The fusing position of Tt-CBD affected the affinity-binding activity to chitin. Recombinant XX, XXC, and CXX were purified to homogeneity and characterized. According to the xylosidase activities, the optimum temperature and pH profiles of the CXX and XXC both in free and immobilized form were the same as those of XX. However, the thermal and pH stabilities of the immobilized XXC and CXX were both greatly improved in the range from 70 to 90 °C and pH 4.2-8.2. The immobilized multifunctional hemicellulase exhibited high stability to producing xylose for at least 19 or 30 times in continuous operation with the achievement of 60% or 80% conversion yield at temperatures up to 65 °C. These results indicate the usefulness of Tt-ChBD as an affinity tag for the simultaneous purification and immobilization of the enzyme on chitin and the great potential applications for thermophilic enzyme immobilization at higher temperatures.

A leguminous trypsin-chymotrypsin inhibitor Limenin with antifungal activity from Phaseolus limensis

A trypsin-chymotrypsin inhibitor, designated Limenin, with both antifungal and antibacterial activity, and exhibiting a molecular mass of 18.0 kDa in SDS-polyacrylamide gel electrophoresis, was isolated from the large lima bean (Phaseolus limensis) legumes by a combination of extraction, ammonium sulfate precipitation, ion exchange chromatography on SP-Toyopearl and high performance liquid chromatography (HPLC) on Mono S. The isoelectric point was estimated to be 7.6 by isoelectric focusing. The 15 N-terminal amino acid sequences were determined to be DFVIDNEGNPLENGG, demonstrating some resemblance to those other protease inhibitors and inhibitor precursors from leguminous plants. It exerted potent antifungal action toward Botrytis cinerea, Alternaria alternata(Fr.) Keissl, and Pythium aphanidermatum. It showed antiproliferative activity toward tumor cells including human liver hepatoma cells Bel-7402 and neuroblastoma cells SHSY5Y. However, it had no effect on bacteria Staphylococcus aureus and Salmonella.

A peptide with potent antifungal and antiproliferative activities from Nepalese large red beans

An antifungal defensin-like peptide with a molecular mass of 7.1kDa was isolated from dried Nepalese large red beans (Phaseolus angularis). The purification protocol employed included ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. The antifungal peptide was unadsorbed on DEAE-cellulose, and adsorbed on Affi-gel blue gel and SP-Sepharose. The antifungal peptide inhibited mycelial growth in Fusarium oxysporum and Mycosphaerella arachidicola with an IC(50) value of 1.4 and 1.8 microM, respectively. It did not inhibit HIV-1 reverse transcriptase when tested up to 200 microM. It exerted an antiproliferative action on L1210 leukemia cells and MBL2 lymphoma cells with an IC(50) of 15 and 60 microM, respectively.

Isolation of a thermostable legume chitinase and study on the antifungal activity

Chitinases are listed as one class of pathogenesis-related proteins, and they have become a popular research topic because of their resistance to plant-pathogenic diseases. A chitinase with antifungal activity was isolated from the Canadian cranberry beans (Phaseolus vulgaris). The procedure included extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, CM-Sephadex C-50, and Sephadex G-75. There was an almost 108-fold increase in specific activity of the purified chitinase compared with that of the crude extract. The enzyme exhibited a molecular mass of 30.6 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis both under reducing and non-reducing conditions, indicating that it was a monomeric protein. The pI was determined to be 7.6 by isoelectric-focusing electrophoresis. The optimum pH and the optimum temperature for activity towards N-acetyl-glucosamine was 5.4 and 40-55 degrees C, respectively. It exerted a potent inhibitory action toward fungal species including Botrytis cinerea, Physalospora piricola, Fusarium oxysporum, and Pythium aphanidermatum. The chitinase was thermostable up to 58 degrees C in both enzymatic reaction and antifungal activity. The present findings demonstrated a thermostable chitinase from cranberry beans with potentially exploitable significance.

Isolation and biochemical characterization of a novel leguminous defense peptide with antifungal and antiproliferative potency

Leguminous plants have formed a popular subject of research owing to the abundance of proteins and peptides with important biological activities that they produce. The antifungal proteins and peptides have been purified from a number of leguminous species. However, research continues to discover novel antifungal plant-produced peptides and proteins are being needed, specially those novel ones with both antifungal activity and other significant bioactivities. The objective of this study was to isolate a novel peptide from Phaseolus limensis. A 6.8 kDa peptide designated Limyin, with both antifungal and antiproliferative activity, was isolated from the large lima bean (P. limensis) legumes. The isolation procedure consisted of extraction, precipitation, affinity chromatography on Affi-gel blue gel, ion chromatography on SP-Toyopearl, and gel filtration on Superdex 75. Its N-terminal sequence was determined to be KTCENLATYYRGPCF, showing high homology to defensin and defensin precursors from plants. It potently suppressed mycelial growth in Alternaria alternata, Fusarium solani, and Botrytis cinerea. Its antifungal activity was stable up to 80 degrees C. It showed antiproliferative activity towards tumor cells including human liver hepatoma cells Bel-7402 and neuroblastoma cells SHSY5Y. However, it had no effect on bacteria Staphylococcus aureus and Salmonella. The present findings make a significant addition of the research on leguminous plants.