Sequencing and Expression of the Gene Encoding the Clostridium stercorarium β-Xylosidase Xyl43B in Escherichia coli
2004
Suryani, | Kimura, Tetsuya | SAKKA, Kazuo | OHMIYA, Kunio
The Clostridium stercorarium F-9 xyl43B gene encoding the β-xylosidase Xyl43B consists of an open reading frame of 1,491 nucleotides that encodes a putative protein, classified in family 43, of 497 amino acids with a predicted molecular weight of 56,355. The deduced amino acid sequence of Xyl43B has sequence similarity with β-xylosidases from Bacteriodes thetaiotaomicron (57% sequence identity), Prevotella ruminicola (45%), Streptomyces coelicolor (40%), and Clostridium acetobutylicum (36%), all of which have been classified in family 43 of the glycoside hydrolases. Xyl43B was purified from a recombinant Escherichia coli and characterized. The optimum pH of the purified enzyme was 3.5 and it was stable over pH from 3.0 to 8.0. Its optimum temperature was 80°C and it showed thermostability in the temperature range from 50 to 70°C. Xyl43B had a K ₘ of 6.2 mM and a V ₘₐₓ of 15 μmol min⁻¹ mg⁻¹ for p-nitrophenyl-β-D-xylopyranoside.
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