Authors: Cristiane Akemi Uchima Gaku Tokuda Hirofumi Watanabe Katsuhiko Kitamoto Manabu Arioka
Publish Date: 2010/11/06
Volume: 89, Issue: 6, Pages: 1761-1771
Abstract
Neotermes koshunensis is a lower termite that secretes endogenous βglucosidase in the salivary glands This βglucosidase G1NkBG was successfully expressed in Aspergillus oryzae G1NkBG was purified to homogeneity from the culture supernatant through ammonium sulfate precipitation and anion exchange hydrophobic and gel filtration chromatographies with a 48fold increase in purity The molecular mass of the native enzyme appeared as a single band at 60 kDa after gel filtration analysis indicating that G1NkBG is a monomeric protein Maximum activity was observed at 50 °C with an optimum pH at 50 G1NkBG retained 80 of its maximum activity at temperatures up to 45 °C and lost its activity at temperatures above 55 °C The enzyme was stable from pH 50 to 90 G1NkBG was most active towards laminaribiose and pnitrophenylβdfucopyranoside Cellobiose as well as cellooligosaccharides was also well hydrolyzed The enzyme activity was slightly stimulated by Mn2+ and glycerol The Km and Vmax values were 077 mM and 16 U/mg respectively against pnitrophenylβdglucopyranoside An unusual finding was that G1NkBG was stimulated by 13fold when glucose was present in the reaction mixture at a concentration of 200 mM These characteristics particularly the stimulation of enzyme activity by glucose make G1NkBG of great interest for biotechnological applications especially for bioethanol productionThis work was supported in part by a grant from Biooriented Technology Research Advancement Institution BRAIN Japan We thank the Ministry of Education Culture Sports Science and Technology of Japan for the scholarship received by CAU The authors are also thankful to the anonymous reviewers for their constructive comments which helped us to improve the manuscript
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