Involved in the biosynthesis of 6-O-methylglucose lipopolysaccarides (MGLPs). Catalyzes the transfer of the glucose moiety from a nuleotide sugar such as UDP-alpha-D-glucose to the position 2 of 3-phospho-D-glycerate (3-PGA) to form glucosyl-3-phosphoglycerate (GPG). It can use UDP-glucose, ADP-glucose and GDP-glucose as sugar donor substrates with decreasing affinity and with 3-PGA as an acceptor. D-glycerate can only be an acceptor with ADP-glucose and at a very low rate. (2R)-3-phosphoglycerate + an NDP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + a ribonucleoside 5'-diphosphate + H(+) (2R)-3-phosphoglycerate + UDP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + H(+) + UDP (2R)-3-phosphoglycerate + ADP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + ADP + H(+) (2R)-3-phosphoglycerate + GDP-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + GDP + H(+) Requires divalent cations for activity. The maximum activity is observed between 20 and 75 mM of MgCl(2). Optimum pH is 8. Optimum temperature is 45 degrees Celsius. The activity is undetectable below 20 and above 55 degrees Celsius. Homotrimer. Belongs to the glycosyltransferase 2 family.