a 1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol + UDP-alpha-D-glucose <=> a 1,2-diacyl-3-O-[beta-D-glucopyranosyl-(1->6)-beta-D-galactopyranosyl]-sn-glycerol + UDP + H(+)
a 1,2-diacyl-3-o-(beta-d-galactosyl)-sn-glycerol + udp-alpha-d-glucose <=> a 1,2-diacyl-3-o-[beta-d-glucopyranosyl-(1->6)-beta-d-galactopyranosyl]-sn-glycerol + udp + h(+)