Uridylyltransferase involved in the biosynthesis of UDP-glucosamine, an essential precursor for glycoprotein and glycolipid synthesis. Can use both UDP-glucosamine and the 4-epimer UDP-galactosamine as substrates, but no other sugars or NTPs (PubMed:20557289). Acts redundantly with GLCNAC1PUT2. 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 Inhibited by hygromycin and streptomycin, but not by gentamycin or kanamycin. Optimum pH is 7.6-8.0. Optimum temperature is 30-37 degrees Celsius. 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. Additional isoforms seem to exist. Expressed in root tips, stipules and mature pollen grains. No visible phenotype under normal growth conditions, but the double mutants glcnac1put1 and glcnac1put2 are lethal. Belongs to the UDPGP type 1 family. Truncated N-terminus.