Catalyzes the reversible phosphorolysis of 2-O-alpha-D-glucosylglycerol with retention of the anomeric configuration, forming alpha-D-glucose 1-phosphate and glycerol. Has most likely a catabolic role, either regulating the intracellular levels of glucosylglycerol, which acts as a compatible solute, or degrading it when the environmental conditions change. Cannot catalyze the phosphorolysis of sucrose or glucosylglycerate. 2-O-(alpha-D-glucopyranosyl)glycerol + phosphate = alpha-D-glucose 1-phosphate + glycerol kcat is 14 sec(-1) towards 2-O-(alpha-D-glucopyranosyl)glycerol for the phosphorolytic direction (at pH 6.5 and 37 degrees Celsius). kcat is 14 sec(-1) towards phosphate for the phosphorolytic direction (at pH 6.5 and 37 degrees Celsius). kcat is 36 sec(-1) towards alpha-D-glucose 1-phosphate for the synthetic direction (at pH 6.5 and 37 degrees Celsius). kcat is 39 sec(-1) towards glycerol for the synthetic direction (at pH 6.5 and 37 degrees Celsius). Optimum pH is 6.5. Optimum temperature is 37 degrees Celsius. Full activity is retained after incubating at up to 45 degrees Celsius for 10 minutes, while only 46% is left after incubating at 50 degrees Celsius. The protein is completely denatured after incubating at higher temperatures. Might be an attractive biocatalyst for the production of the osmolyte glucosylglycerol, which is currently produced on industrial scale by exploiting a side activity of the closely related sucrose phosphorylase. GGoP from M.adhaerens may offer far higher productivities due to its high specific activity in the synthesis direction. Glucosylglycerol is commercially distributed as a moisturising agent in cosmetics and can also serve as a stabilizing agent in protein formulations, or even as a functional food. Belongs to the glycosyl hydrolase 13 family. Sucrose phosphorylase subfamily.