Glycosyl transferase activity in the brush border membrane of Hymenolepis diminuta.

The isolated brush border membrane of Hymenolepis diminuta incorporates radiolabeled glucose when incubated in the presence of uridine diphospho(UDP)-D-(6-3H)glucose. The pH optimum for incorporation was 7.0 to 7.2 regardless of the buffer used. Transferase activity was maximal in 200 mM Tris buffer; 100 mM phosphate buffer inhibited significantly the incorporation of radiolabeled glucose, whereas 50 mM Tris-maleate and 100 mM PIPES resulted in moderate inhibition of activity. Incorporation of labeled glucose was not inhibited by low concentrations (0.01%) of Triton X-100, but activity was inhibited 50% by 0.25% Triton X-100. Addition of divalent cations to the brush border membrane preparation did not activate transferase activity, but addition of chelating agents (i.e., EDTA or EGTA) inhibited transferase activity nearly 90%. Incorporation of labeled glucose was inhibited by UDP, guanosine diphosphate (GDP), UDP- and GDP-activated monosaccharides, and monosaccharides, indicating that the transferase activity lacked substrate specificity.