title: Cloning, expression and characterization of a phosphoglucomutase/phosphomannomutase from sphingan-producing Sphingomonas sanxanigenens.
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).
authors.affiliation: Department of Agronomy, Tianjin Agricultural University, Tianjin, 300384, China. hdhuang@tjau.edu.cn
authors.forename: Haidong
authors.initials: H
authors.lastname: Huang
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Wu
authors.forename: Shengxiu
authors.initials: S
authors.lastname: Wang
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Li
authors.forename: Ting
authors.initials: T
authors.lastname: Ma
mesh_terms: D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010733:Phosphoglucomutase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D017875:Phosphotransferases (Phosphomutases) / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D020578:Sphingomonas / Q000201:enzymology* / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D011994:Recombinant Proteins; C430406:sphingan; D017875:Phosphotransferases (Phosphomutases); D010733:Phosphoglucomutase; C052799:phosphomannomutase