Catalyzes the initial step of dolichol-linked oligosaccharide biosynthesis in N-linked protein glycosylation pathway: transfers GlcNAc-1-P from UDP-GlcNAc onto the carrier lipid dolichyl phosphate (P-dolichol), yielding GlcNAc-P-P-dolichol. a dolichyl phosphate + UDP-N-acetyl-alpha-D-glucosamine = N-acetyl-alpha-D-glucosaminyl-diphosphodolichol + UMP Activated by mannosylphosphoryldolichol and phospholipids such as phosphatidylglycerol and phosphatidylcholine (Probable). Inhibited by natural nucleoside antibiotic tunicamycin, which acts as a structural analog and competitor of UDP-GlcNAc (PubMed:9451016, PubMed:29459785, PubMed:30388443). kcat is 0.21 min(-1) with UDP-N-acetylglucosamine. kcat is 0.20 min(-1) with dolichol phosphate. Protein modification; protein glycosylation. Homodimer. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyltransferase 4 family. UDP-N-acetylglucosamine--dolichyl-phosphate N-acetylglucosaminephosphotransferase