Mannosylglucosyl-3-phosphoglycerate synthase (, MggA) is an enzyme with systematic name GDP-mannose:2-O-(alpha-D-glucosyl)-3-phospho-D-glycerate 2-O-alpha-D-mannosyltransferase. This enzyme catalyses the following chemical reaction
The enzyme is involved in synthesis of 2-[2-O-(alpha-D-mannopranosyl)-alpha-D-glucopyranosyl]-D-glycerate.