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KMID : 0545120180280071122
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Journal of Microbiology and Biotechnology
2018 Volume.28 No. 7 p.1122 ~ p.1132
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Characterization of Ribose-5-Phosphate Isomerase B from Newly Isolated Strain Ochrobactrum sp. CSL1 Producing L-Rhamnulose from L-Rhamnose
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Shen Min
Ju Xin
Xu Xinqi
Yao Xuemei
Li Liangzhi
Chen Jiajia
Hu Cuiying
Fu Jiaolong
Yan Lishi
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Abstract
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In this study, we attempted to find new and efficient microbial enzymes for producing rare sugars. A ribose-5-phosphate isomerase B (OsRpiB) was cloned, overexpressed, and preliminarily purified successfully from a newly screened Ochrobactrum sp. CSL1, which could catalyze the isomerization reaction of rare sugars. A study of its substrate specificity showed that the cloned isomerase (OsRpiB) could effectively catalyze the conversion of L-rhamnose to L-rhamnulose, which was unconventional for RpiB. The optimal reaction conditions (50oC, pH 8.0, and 1 mM Ca2+) were obtained to maximize the potential of OsRpiB in preparing L-rhamnulose. The catalytic properties of OsRpiB, including Km, kcat, and catalytic efficiency (kcat/Km), were determined as 43.47 mM, 129.4 sec-1, and 2.98 mM/sec. The highest conversion rate of L-rhamnose under the optimized conditions by OsRpiB could reach 26% after 4.5 h. To the best of our knowledge, this is the first successful attempt of the novel biotransformation of L-rhamnose to L-rhamnulose by OsRpiB biocatalysis.
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KEYWORD
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L-rhamnose, L-rhamnulose, Ochrobactrum sp. CSL1, Rare sugar, Ribose-5-phosphate isomerase B
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