Substrate specificity of a recombinant ribose-5-phosphate isomerase from Streptococcus pneumoniae and its application in the production of L-lyxose and L-tagatose
2011
Park, Chang-Su | Yeom, Soo-Jin | Lim, Yu-Ri | Kim, Yeong-Su | Oh, Deok-Kun
A putative ribose-5-phosphate isomerase (RpiB) from Streptococcus pneumoniae was purified with a specific activity of 26.7 U mg−1 by Hi-Trap Q HP anion exchange and Sephacryl S-300 HR 16/60 gel filtration chromatographies. The native enzyme existed as a 96-kDa tetramer with activity maxima at pH 7.5 and 35°C. The RpiB exhibited isomerization activity with L-lyxose, L-talose, D-gulose, D-ribose, L-mannose, D-allose, L-xylulose, L-tagatose, D-sorbose, D-ribulose, L-fructose, and D-psicose and exhibited particularly high activity with L-form monosaccharides such as L-lyxose, L-xylulose, L-talose, and L-tagatose. With L-xylulose (500 g l−1) and L-talose (500 g l−1) substrates, the optimum concentrations of RpiB were 300 and 600 U ml−1, respectively. The enzyme converted 500 g l−1 L-xylulose to 350 g l−1 L-lyxose after 3 h, and yielded 450 g l−1 L-tagatose from 500 g l−1 L-talose after 5 h. These results suggest that RpiB from S. pneumoniae can be employed as a potential producer of L-form monosaccharides.
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