Specific inhibitors of transport

Glucose transport in the erythrocyte is also potently inhibited by a series of biphenolic compounds, including diethylstilboestrol and related compounds, and phloretin, whose structures are shown in Fig. 1. Diethylstilboestrol inhibits transport with a K of about 5 [35] and phloretin inhibits with a K of about 2 /rM [36]. 

Kinetic experiments have shown that phloretin binds asymmetrically to the glucose transporter [37]. However, unlike cytochalasin B it binds exclusively to the extracellular surface of the membrane. Similar asymmetries of binding have been reported for a number of steroids that inhibit glucose transport [38]. For example, androsten-4-ene-3,17-dione (Fig. 1) which inhibits with a K of about 20/rM, binds almost exclusively at the inner surface of the membrane. 

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