A comparison of phlorizin and phloretin adsorption by the tapeworm Hymenolepis diminuta.

Phloretin and phlorizin adsorb to the tegument surface of Hymenolepis diminuta, with KDs of 2.39 mM and 14.7 microM, respectively, and Vmaxs of 1446 and 12.54 nmoles/g tissue per 2 min, respectively. Phloretin adsorption is not inhibited by phlorizin or glucose. Glucose partially inhibits phlorizin adsorption. Phlorizin, but not phloretin, adsorption to isolated tegument brush border membrane preparations is partially inhibited by N-ethylmaleimide. No indications of phlorizin hydrolysis to phloretin during incubation with H. diminuta were obtained. The data are supportive of spacially separate and distinct binding sites for phloretin and phlorizin in the tegument brush border.