In enzymology, an undecaprenyldiphospho-muramoylpentapeptide beta-N-acetylglucosaminyltransferase is an enzyme that catalyzes the chemical reaction The 2 substrates of this enzyme are UDP-N-acetylglucosamine and Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)-diphosphoundecaprenol, whereas its 2 products are UDP and Lipid II. This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-N-acetyl-D-glucosamine:N-acetyl-alpha-D-muramyl(oyl-L-Ala-gamma- D-Glu-L-Lys-D-Ala-D-Ala)-diphosphoundecaprenol beta-1,4-N-acetylglucosaminlytransferase. Another name in common use is MurG transferase. This enzyme participates in peptidoglycan biosynthesis. Variant reactions producing modified cell walls include (not muturally exclusive):