In enzymology, an undecaprenyl-phosphate galactose phosphotransferase (EC 2.7.8.6) is an enzyme that catalyzes the chemical reaction

UDP-galactose + undecaprenyl phosphate UMP + alpha-D-galactosyl-diphosphoundecaprenol

Thus, the two substrates of this enzyme are UDP-galactose and undecaprenyl phosphate, whereas its two products are UMP and alpha-D-galactosyl-diphosphoundecaprenol.

This enzyme belongs to the family of transferases, specifically those transferring non-standard substituted phosphate groups. The systematic name of this enzyme class is UDP-galactose:undecaprenyl-phosphate galactose phosphotransferase. Other names in common use include poly(isoprenol)-phosphate galactose phosphotransferase, poly(isoprenyl)phosphate galactosephosphatetransferase, and undecaprenyl phosphate galactosyl-1-phosphate transferase.

• Osborn MJ, Tze-Yuen RY (1968). "Biosynthesis of bacterial lipopolysaccharide. VII. Enzymatic formation of the first intermediate in biosynthesis of the O-antigen of Salmonella typhimurium". J. Biol. Chem. 243 (19): 5145–52. doi:10.1016/S0021-9258(18)92003-X. PMID 4878433.
• Wright A, Dankert M, Fennessey P, Robbins PW (1967). "Characterization of a polyisoprenoid compound functional in O-antigen biosynthesis". Proc. Natl. Acad. Sci. U.S.A. 57 (6): 1798–803. Bibcode:1967PNAS...57.1798W. doi:10.1073/pnas.57.6.1798. PMC 224549. PMID 4291948.