Catalyzes the hydrolysis of glucosylglycerate (GG) to glycerate and glucose (PubMed:25341489, PubMed:31316802). Involved in recovery from nitrogen starvation by promoting the rapid mobilization of the glucosylglycerate that accumulates under these conditions (PubMed:25341489). Can also hydrolyze mannosylglycerate (MG), with tenfold lower efficiency (PubMed:31316802). (2R)-2-O-(alpha-D-glucopyranosyl)-glycerate + H2O = (R)-glycerate + D-glucose Activity is not dependent on divalent cations, but it is enhanced by Mg(2+). Optimum pH is 6.0 (tag-less variant) (PubMed:31316802). Optimum pH is 5.8 (C-terminally tagged variant) (PubMed:25341489). Optimum temperature is 50-55 degrees Celsius (tag-less variant) (PubMed:31316802). Optimum temperature is 42 degrees Celsius (C-terminally tagged variant) (PubMed:25341489). Homotetramer. Dimer of dimers. Up-regulated in response to nitrogen shock. Belongs to the glycosyl hydrolase 63 family.