Identification of the pgmG gene, encoding a bifunctional protein with phosphoglucomutase and phosphomannomutase activities, in the gellan gum-producing strain Sphingomonas paucimobilis ATCC 31461.
The pgmG gene of Sphingomonas paucimobilis ATCC 31461, the industrial gellan gum-producing strain, was cloned and sequenced. It encodes a 50,059-Da polypeptide that has phosphoglucomutase (PGM) and phosphomannomutase (PMM) activities and is 37 to 59% identical to other bifunctional proteins with PGM and PMM activities from gram-negative species, including Pseudomonas aeruginosa AlgC. Purified PgmG protein showed a marked preference for glucose-1-phosphate (G1P); the catalytic efficiency was about 50-fold higher for G1P than it was for mannose-1-phosphate (M1P). The estimated apparent K(m) values for G1P and M1P were high, 0.33 and 1.27 mM, respectively. The pgmG gene allowed the recovery of alginate biosynthetic ability in a P. aeruginosa mutant with a defective algC gene. This result indicates that PgmG protein can convert mannose-6-phosphate into M1P in the initial steps of alginate biosynthesis and, together with other results, suggests that PgmG may convert glucose-6-phosphate into G1P in the gellan pathway.
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Centro de Engenharia Biológica e Química, Instituto Superior Técnico, 1049-001 Lisbon, Portugal.
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D006090:Gram-Negative Bacteria / Q000201:enzymology / Q000235:genetics; D007700:Kinetics; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism*; D017875:Phosphotransferases (Phosphomutases) / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D020578:Sphingomonas / Q000201:enzymology* / Q000235:genetics*; D013379:Substrate Specificity
D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D011135:Polysaccharides, Bacterial; C048288:gellan gum; C409188:PgmG protein, Sphingomonas paucimobilis; D017875:Phosphotransferases (Phosphomutases); C052799:phosphomannomutase