Fig. 4.

Kinetic properties. A: steady-state kinetics of d-glucose transport by hSGLT2 at 37°C and V_m = −60 mV. Glucose-induced currents are plotted against extracellular glucose concentration, and the curves represent the data fit to the Hill equation (Eq. 2) with the Hill coefficient, n_h, constrained to 1. Maximal glucose-induced current (I_max^d-glucose) indicates the level of expression in a given cell, whereas the glucose concentration at half-maximal current (K_0.5^d-glucose) reflects the transporter's apparent affinity for glucose. B: steady-state kinetics of Na⁺ activation of hSGLT2, 37°C and V_m = −60 mV. Inward, 100 mM glucose-induced current is plotted as a function of extracellular Na⁺ concentration and the data are fitted to the Hill equation, maximal current (I_max), n_h, and apparent Na⁺ affinity (K_0.5^Na) values. The statistics for maximal current (I_max^Na) and apparent Na⁺ affinity (K_0.5^Na) in B (as in A for sugar) are SEs of the fit. For both substrates, K_0.5 values were averaged from multiple cells and compared with those from hSGLT1 (Table 1).