n UDP-glucose + 4-O-{Poly[(2R)-glycerophospho]-(2R)-glycerophospho}-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl-diphospho-ditrans,octacis-undecaprenol <=> n UDP + 4-O-{Poly[(2R)-2-alpha-D-glucosyl-1-glycerophospho]-(2R)-glycerophospho}-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl-diphospho-ditrans,octacis-undecaprenol