Inactivation of Glucose Carriers in Human Erythrocyte Membranes by 1-Fluoro-2,4-dinitrobenzene

Inactivation of the glucose transport carrier activities of isolated human erythrocyte membranes by 1-fluoro-2,4-dinitrobenzene (FDNB) was studied in the presence and the absence of d-glucose and correlated with accompanying dinitrophenylation of the membrane components. The inactivation was greatly enhanced by the presence of the sugar. Furthermore, the kinetics of inactivation in the presence of of the sugar differed from that seen in the absence of the sugar. In the absence of glucose, the inactivation was first order with respect to FDNB and had an activation energy of 32 Cal per mole. In the presence of the sugar, the inactivation was nearly second order with respect to FDNB and had an activation energy of 17 Cal per mole. The pH dependence of the inactivation was also significantly modified by the presence of the sugar. Neither the total amount of dinitrophenylation nor the kinetics of this process was significantly altered by the presence of the sugar. The kinetics of dinitrophenylation was similar to the kinetics of the inactivation in the absence of the sugar, but significantly different from that in the presence of the sugar. The inactivation of the glucose carrier by FDNB involves at least two mutually distinct reactivities of the carrier, namely glucose-independent and glucose-dependent dinitrophenylations. These reactivities may represent two different conformational states of the carrier in its operation.