Journal
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
Volume 108, Issue -, Pages 98-104Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ijbiomac.2017.11.154
Keywords
alpha-Galactosidases; Bacillus megaterium; Protease resistance; High hydrolytic activity; Raffinose family oligosaccharides
Funding
- Natural Science Foundation of China [31400056, 31570059]
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A novel alpha-galactosidase gene (agaB) from Bacillus megaterium 3-7 was cloned and expressed in Escherichia coli. The gene coded for a protein with 741 amino acids and a calculated molecular mass of 85.4 kDa. The native structure of the recombined AgaB was determined to be a homotrimer. AgaB showed the highest identity of 57% with the characterized glycosyl hydrolase family 36 alpha-galactosidase from Clostridium stercoraritan F-9. The enzyme exhibited a specific activity of 362.6 U/mg at 37 degrees C and pH 6.8. The enzyme showed strong resistance to proteases and great tolerance to galactose (K-i = 12.5 mM). AgaB displayed wide substrate specificity toward pNPGal, melibiose, raffinose and stachyose, with a K-m of 0.42, 12.1, 17.0 and 25.4 mM, respectively. Furthermore, AgaB completely hydrolyzed raffinose and stachyose present in soybean milk at 37 degrees C within 4 h when combined with trypsin. These favorable properties make AgaB a potential candidate for applications in the food and feed industries. (C) 2017 Elsevier B.V. All rights reserved.
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