preferred_name: N(4)-[alpha-D-mannosyl-(1->2)-alpha-D-mannosyl-(glycan)]-L-asparaginyl-[protein] + UDP-N-acetyl-alpha-D-glucosamine => N(4)-[6-(N-acetyl-alpha-D-glucosaminyl-1-phospho)-alpha-D-mannosyl-(1->2)-alpha-D-mannosyl-(glycan)]-L-asparaginyl-[protein] + UMP + H(+)