PMID:10585410

Citation	Martins, LO, Empadinhas, N, Marugg, JD, Miguel, C, Ferreira, C, da Costa, MS and Santos, H (1999) Biosynthesis of mannosylglycerate in the thermophilic bacterium Rhodothermus marinus. Biochemical and genetic characterization of a mannosylglycerate synthase. J. Biol. Chem. 274:35407-14
Abstract	The biosynthetic reaction scheme for the compatible solute mannosylglycerate in Rhodothermus marinus is proposed based on measurements of the relevant enzymatic activities in cell-free extracts and in vivo (13)C labeling experiments. The synthesis of mannosylglycerate proceeded via two alternative pathways; in one of them, GDP mannose was condensed with D-glycerate to produce mannosylglycerate in a single reaction catalyzed by mannosylglycerate synthase, in the other pathway, a mannosyl-3-phosphoglycerate synthase catalyzed the conversion of GDP mannose and D-3-phosphoglycerate into a phosphorylated intermediate, which was subsequently converted to mannosylglycerate by the action of a phosphatase. The enzyme activities committed to the synthesis of mannosylglycerate were not influenced by the NaCl concentration in the growth medium. However, the combined mannosyl-3-phosphoglycerate synthase/phosphatase system required the addition of NaCl or KCl to the assay mixture for optimal activity. The mannosylglycerate synthase enzyme was purified and characterized. Based on partial sequence information, the corresponding mgs gene was identified from a genomic library of R. marinus. In addition, the mgs gene was overexpressed in Escherichia coli with a high yield. The enzyme had a molecular mass of 46,125 Da, and was specific for GDP mannose and D-glycerate. This is the first report of the characterization of a mannosylglycerate synthase.
Links	PubMed
Keywords	Amino Acid Sequence; Base Sequence; Enzyme Stability; Glyceric Acids/metabolism; Gram-Negative Aerobic Bacteria/enzymology; Gram-Negative Aerobic Bacteria/genetics; Hot Temperature; Kinetics; Mannose/analogs & derivatives; Mannose/metabolism; Mannosyltransferases/chemistry; Mannosyltransferases/genetics; Mannosyltransferases/metabolism; Models, Chemical; Molecular Sequence Data; Recombinant Proteins/chemistry; Recombinant Proteins/metabolism; Restriction Mapping; Thermodynamics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RHOMR:MGS		GO:0051479: mannosylglycerate biosynthetic process	ECO:0000314:		P		Table 2 shows the activity of the native and recombinant enzymes and their ability to utilize substrates in the mannosylglycerate biosynthetic pathway. The native enzyme was obtained by electroelution and had a specific activity of 70mmol/min/mg of protein. The substrates used to determine the specificity of Mgs were GDP mannose, ADP mannose, UDP mannose,mannose 1-phosphate, and mannose 6-phosphate as sugar donors,and D-glycerate,L-glycerate, and D-3-P-glycerate as sugar acceptors. GDP glucose, UDP glucose, and ADP glucose were tested as sugar donors, and glycerol 3-phosphate, glucose 6-phosphate,glucose 1-phosphate, and glucose as sugar acceptors in an effort to also identify the ability of Mgs to catalyze the synthesis of other glycosylconjugates. Mgs was specific for GDP mannose and D-glycerate and had an absolute stereospecificity for D-glycerate. UDP mannose and GDP mannose were the only sugar nucleotides used by the enzyme. UDP mannose was used very little, less than 3% of that of GDP mannose. NaCl and KCl (50-500 mM concentrations) had no effect on enzyme activity. However, Mg2+ was required for optimal activity shown by the 2.5-fold lower activity in absence of the cation.	complete CACAO 4456
RHOMR:MGS	involved_in	GO:0051479: mannosylglycerate biosynthetic process	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

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