Cloning, expression and characterization of a phosphoglucomutase/phosphomannomutase from sphingan-producing Sphingomonas sanxanigenens |
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Authors: | Haidong Huang Xiaoyan Li Mengmeng Wu Shengxiu Wang Guoqiang Li Ting Ma |
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Institution: | 1. Department of Agronomy, Tianjin Agricultural University, Tianjin, 300384, China 2. Department of Food Science, Tianjin Agricultural University, Tianjin, 300384, China 3. Key Laboratory of Molecular Microbiology Technology, Ministry of Education, College of Life Sciences, Nankai University, Tianjin, 300071, China
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Abstract: | Several strains of the genus Sphingomonas produce sphingans, extracellular polysaccharides used as thickeners, emulsifiers and gelling agents. The pgmG gene from Sphingomonas sanxanigenens, which encodes a bifunctional protein with phosphoglucomutase and phosphomannomutase activities, was cloned and sequenced. The predicted amino acid sequence of the PgmG protein possessed 460 amino acids and a calculated molecular mass of 49.8 kDa, and it was 80 % identical to PGM/PMM from S. elodea. We overexpressed pgmG in Escherichia coli, and the purified protein displayed a K m of 0.2 mM and a V max of 1.3 μmol min?1 mg?1 with glucose 1-phosphate as substrate. The catalytic efficiency (K cat/K m) of PgmG was about 15-fold higher for glucose 1-phosphate than for mannose 1-phosphate. Overexpression of pgmG in S. sanxanigenens resulted in a 17 ± 0.3 % increase in sphingan production to ~12.5 g l?1. |
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