Uridylyltransferase involved in the biosynthesis of UDP-glucosamine, an essential precursor for glycoprotein and glycolipid synthesis. Can use UDP-glucosamine, the 4-epimer UDP-galactosamine and UDP-glucose as substrates (PubMed:20557289). Acts redundantly with GLCNAC1PUT1. Required for gametogenesis and embryo development (PubMed:25231969). H(+) + N-acetyl-alpha-D-glucosamine 1-phosphate + UTP = diphosphate + UDP-N-acetyl-alpha-D-glucosamine H(+) + N-acetyl-alpha-D-galactosamine 1-phosphate + UTP = diphosphate + UDP-N-acetyl-alpha-D-galactosamine alpha-D-glucose 1-phosphate + H(+) + UTP = diphosphate + UDP-alpha-D-glucose Nucleotide-sugar biosynthesis; UDP-N-acetyl-alpha-D-glucosamine biosynthesis; UDP-N-acetyl-alpha-D-glucosamine from N-acetyl-alpha-D-glucosamine 1-phosphate: step 1/1. Monomer. Expressed in root tips, stipules, lateral root primordia, immature anthers and at the branching points of the flowering shoots. No visible phenotype under normal growth conditions, but the double mutants glcnac1put1 and glcnac1put2 are lethal. Belongs to the UDPGP type 1 family.