Purification and characterization of a novel protease-resistant α-galactosidase from Rhizopus sp. F78 ACCC 30795

A thermophilic fungal GH36 α-galactosidase from Lichtheimia ramosa and its synergistic hydrolysis of locust bean gum

A novel GH36 α-galactosidase gene (LrAgal36A) from Lichtheimia ramosa was synthesized and highly expressed in Pichia pastoris. The enzyme titer and protein yield for high-density fermentation in a 5 L fermentor were up to 953.6 U mL^-1 and 4.36 g L^-1. Purified recombinant LrAgal36A showed the maximum activity at pH 6.0 and 65 °C and was thermostable with a half-life of 70 min at 60 °C. LrAgal36A displayed the highest specific activity (353.17 ± 4.19 U mg^-1) toward p-nitrophenyl-α-d-galactopyranoside (pNPGal) followed by galacto-oligosaccharides and could act slightly on galactomannans. The K_m and catalytic efficiency (k_cat/K_m) of LrAgal36A for pNPGal were 0.33 mM and 1569.50 mM^-1 s^-1, respectively. LrAgal36A and GH5 β-mannanase from L. ramosa showed a significant synergistic effect on the degradation of locust bean gum (LBG), resulting in release more reducing sugars (1.56 folds) and galactose (7.6 folds) by simultaneous or sequential reactions. Due to its hydrolysis properties, LrAgal36A might have potential applications in the area of pulp biobleaching, feed and food processing.

A novel α-galactosidase from the thermophilic probiotic Bacillus coagulans with remarkable protease-resistance and high hydrolytic activity

A novel α-galactosidase of glycoside hydrolase family 36 was cloned from Bacillus coagulans, overexpressed in Escherichia coli, and characterized. The purified enzyme Aga-BC7050 was 85 kDa according to SDS-PAGE and 168 kDa according to gel filtration, indicating that its native structure is a dimer. With p-nitrophenyl-α-d- galactopyranoside (pNPGal) as the substrate, optimal temperature and pH were 55 °C and 6.0, respectively. At 60 °C for 30 min, it retained > 50% of its activity. It was stable at pH 5.0–10.0, and showed remarkable resistance to proteinase K, subtilisin A, α-chymotrypsin, and trypsin. Its activity was not inhibited by glucose, sucrose, xylose, or fructose, but was slightly inhibited at galactose concentrations up to 100 mM. Aga-BC7050 was highly active toward pNPGal, melibiose, raffinose, and stachyose. It completely hydrolyzed melibiose, raffinose, and stachyose in < 30 min. These characteristics suggest that Aga-BC7050 could be used in feed and food industries and sugar processing.

Characterization of a Glycoside Hydrolase Family 27 α-Galactosidase from Pontibacter Reveals Its Novel Salt-Protease Tolerance and Transglycosylation Activity

α-Galactosidases are of great interest in various applications. A glycoside hydrolase family 27 α-galactosidase was cloned from Pontibacter sp. harbored in a saline soil and expressed in Escherichia coli. The purified recombinant enzyme (rAgaAHJ8) was little or not affected by 3.5-30.0% (w/v) NaCl, 10.0-100.0 mM Pb(CH3COO)2, 10.0-60.0 mM ZnSO4, or 8.3-100.0 mg mL(-1) trypsin and by most metal ions and chemical reagents at 1.0 and 10.0 mM concentrations. The degree of synergy on enzymatic degradation of locust bean gum and guar gum by an endomannanase and rAgaAHJ8 was 1.22-1.54. In the presence of trypsin, the amount of reducing sugars released from soybean milk treated by rAgaAHJ8 was approximately 3.8-fold compared with that treated by a commercial α-galactosidase. rAgaAHJ8 showed transglycosylation activity when using sucrose, raffinose, and 3-methyl-1-butanol as the acceptors. Furthermore, potential factors for salt adaptation of the enzyme were presumed.

N-Glycosylation Improves the Pepsin Resistance of Histidine Acid Phosphatase Phytases by Enhancing Their Stability at Acidic pHs and Reducing Pepsin's Accessibility to Its Cleavage Sites

N-Glycosylation can modulate enzyme structure and function. In this study, we identified two pepsin-resistant histidine acid phosphatase (HAP) phytases from Yersinia kristensenii (YkAPPA) and Yersinia rohdei (YrAPPA), each having an N-glycosylation motif, and one pepsin-sensitive HAP phytase from Yersinia enterocolitica (YeAPPA) that lacked an N-glycosylation site. Site-directed mutagenesis was employed to construct mutants by altering the N-glycosylation status of each enzyme, and the mutant and wild-type enzymes were expressed in Pichia pastoris for biochemical characterization. Compared with those of the N-glycosylation site deletion mutants and N-deglycosylated enzymes, all N-glycosylated counterparts exhibited enhanced pepsin resistance. Introduction of the N-glycosylation site into YeAPPA as YkAPPA and YrAPPA conferred pepsin resistance, shifted the pH optimum (0.5 and 1.5 pH units downward, respectively) and improved stability at acidic pH (83.2 and 98.8% residual activities at pH 2.0 for 1 h). Replacing the pepsin cleavage sites L197 and L396 in the immediate vicinity of the N-glycosylation motifs of YkAPPA and YrAPPA with V promoted their resistance to pepsin digestion when produced in Escherichia coli but had no effect on the pepsin resistance of N-glycosylated enzymes produced in P. pastoris. Thus, N-glycosylation may improve pepsin resistance by enhancing the stability at acidic pH and reducing pepsin's accessibility to peptic cleavage sites. This study provides a strategy, namely, the manipulation of N-glycosylation, for improvement of phytase properties for use in animal feed.

Production of a Highly Protease-Resistant Fungal α-Galactosidase in Transgenic Maize Seeds for Simplified Feed Processing

Raffinose-family oligosaccharide (RFO) in soybeans is one of the major anti-nutritional factors for poultry and livestocks. α-Galactosidase is commonly supplemented into the animal feed to hydrolyze α-1,6-galactosidic bonds on the RFOs. To simplify the feed processing, a protease-resistant α-galactosidase encoding gene from Gibberella sp. strain F75, aga-F75, was modified by codon optimization and heterologously expressed in the embryos of transgentic maize driven by the embryo-specific promoter ZM-leg1A. The progenies were produced by backcrossing with the commercial inbred variety Zheng58. PCR, southern blot and western blot analysis confirmed the stable integration and tissue specific expression of the modified gene, aga-F75m, in seeds over four generations. The expression level of Aga-F75M reached up to 10,000 units per kilogram of maize seeds. In comparison with its counterpart produced in Pichia pastoris strain GS115, maize seed-derived Aga-F75M showed a lower temperature optimum (50 °C) and lower stability over alkaline pH range, but better thermal stability at 60 °C to 70 °C and resistance to feed pelleting inactivation (80 °C). This is the first report of producing α-galactosidase in transgenic plant. The study offers an effective and economic approach for direct utilization of α-galactosidase-producing maize without any purification or supplementation procedures in the feed processing.

Purification and characterization of an α-galactosidase from Phaseolus coccineus seeds showing degrading capability on raffinose family oligosaccharides

An acidic α-galactosidase (EC 3.2.1.22) designated as Phaseolus coccineus seeds galactosidase (PCG) was purified from P. coccineus seeds using ion-exchange chromatography on DEAE- and CM-cellulose, Q- and SP-Sepharose and gel filtration on Superdex 75. The molecular weight of PCG was 43 kDa as judged by SDS-PAGE and gel filtration. Two inner peptides of PCG were sequenced by MALDI-TOF-MS. The optimum pH and temperature was 3.0 and 70 °C, respectively but was stable up to 60 °C for 30 min. The enzyme activity was inhibited by NBS signifying the pivotal role played by tryptophan in the catalytic activity of the enzyme. The Km for hydrolysis of pNPGal was 0.0025 mM. Besides hydrolyzing pNPGal, α-galactosidases also hydrolyzed natural substrates such as melibiose, raffinose and stachyose. Hence it can be exploited commercially for improving the nutritional value of soymilk. Thus the PCG has great potential in the feed industries for removal of non-digestible oligosaccharide from legumes.

Purification and characterization of Aspergillus terreus α-galactosidases and their use for hydrolysis of soymilk oligosaccharides

α-Galactosidases has the potential to hydrolyze α-1-6 linkages in raffinose family oligosaccharides (RFO). Aspergillus terreus cells cultivated on wheat bran produced three extracellular forms of α-galactosidases (E1, E2, and E3). E1 and E2 α-galactosidases presented maximal activities at pH 5, while E3 α-galactosidase was more active at pH 5.5. The E1 and E2 enzymes showed stability for 6 h at pH 4-7. Maximal activities were determined at 60, 55, and 50 °C, for E1, E2, and E3 α-galactosidase, respectively. E2 α-galactosidase retained 90% of its initial activity after 70 h at 50 °C. The enzymes hydrolyzed ρNPGal, melibiose, raffinose and stachyose, and E1 and E2 enzymes were able to hydrolyze guar gum and locust bean gum substrates. E1 and E3 α-galactosidases were completely inhibited by Hg²⁺, Ag⁺, and Cu²⁺. The treatment of RFO present in soy milk with the enzymes showed that E1 α-galactosidase reduced the stachyose content to zero after 12 h of reaction, while E2 promoted total hydrolysis of raffinose. The complete removal of the oligosaccharides in soy milk could be reached by synergistic action of both enzymes.

A thermophilic and acid stable family-10 xylanase from the acidophilic fungus Bispora sp. MEY-1

A complete gene, xyl10C, encoding a thermophilic endo-1,4-beta-xylanase (XYL10C), was cloned from the acidophilic fungus Bispora sp. MEY-1 and expressed in Pichia pastoris. XYL10C shares highest nucleotide and amino acid sequence identities of 57.3 and 49.7%, respectively, with a putative xylanase from Aspergillus fumigatus Af293 of glycoside hydrolase family 10. A high expression level in P. pastoris (73,400 U ml(-1)) was achieved in a 3.7-l fermenter. The purified recombinant XYL10C was thermophilic, exhibiting maximum activity at 85 degrees C, which is higher than that reported from any fungal xylanase. The enzyme was also highly thermostable, exhibiting approximately 100% of the initial activity after incubation at 80 degrees C for 60 min and >87% of activity at 90 degrees C for 10 min. The half lives of XYL10C at 80 and 85 degrees C were approximately 45 and 3 h, respectively. It had two activity peaks at pH 3.0 and 4.5-5.0 (maximum), respectively, and was very acid stable, retaining more than 80% activity after incubation at pH 1.5-6.0 for 1 h. The enzyme was resistant to Co(2+), Mn(2+), Cr(3+) and Ag(+). The specific activity of XYL10C for oat spelt xylan was 18,831 U mg(-1). It also had wide substrate specificity and produced simple products (65.1% xylose, 25.0% xylobiose and 9.9% xylan polymer) from oat spelt xylan.

Cloning and functional expression of an alpha-galactosidase from Yersinia pestis biovar Microtus str. 91001

A gene encoding a glycoside hydrolase (GH) family 36 alpha-galactosidase was cloned from Yersinia pestis biovar Microtus str. 91001 and expressed in Escherichia coli. The purified recombinant alpha-galactosidase (Aga-Y) was optimally active at 37 degrees C and pH 6.8. The features of temperature profile, thermoliability, kinetics, and amino acid composition indicated that Aga-Y had properties of a cold-adapted enzyme.