Incubation of pig liver microsomal preparations with UDP-N[U-14C]acetylglucosamine yields a 14C-labelled lipid. The requirement for Mn2+, the pH optimum, time-dependence and the reversibility by UMP of the transferase are reported. Evidence is presented in favour of the lipid being a mixture of dolichol diphosphate N-[14C]acetylglucosamine and dolichol diphosphate N-[14C]acetylmannosamine. Available data suggest that the epimerization takes place while the hexosamine is bound in this lipid-soluble form. The N-acetylmannosamine appeared not be be released into the medium. The subfractionation of the microsomal fraction to separate transferase activity from membrane-bound β-N-acetylglucosaminidase activity is also reported.
