D-Man-alpha-(1->3) -D-Glc-beta-(1->4) -D-Glc-alpha-1-diphosphoundecaprenol 2-beta-glucuronyltransferase (, GumK) is an enzyme with the systematic name UDP-glucuronate: D-Man-alpha-(1->3) -D-Glc-beta-(1->4)-D-Glc-alpha-1-diphospho-ditrans,octacis-undecaprenol beta-1,2-glucuronyltransferase. This enzyme catalyses the following chemical reaction:
The enzyme is involved in the biosynthesis of the exopolysaccharides xanthan (in the bacterium Xanthomonas campestris) and acetan (in the bacterium Gluconacetobacter xylinus).