PMID: 7372586May 25, 1980Paper

The mechanism of Na+-dependent D-glucose transport.

The Journal of Biological Chemistry
U Hopfer, R Groseclose

Abstract

The mechanism of Na+-dependent D-glucose transport was investigated by kinetic means in rabbit small intestinal and renal brush border membranes. The rate of glucose transport was measured under equilibrium exchange conditions as a function of its own concentration and of the Na+ concentration. Likewise, the rate of Na+ transport was measured as a function of the D-glucose concentration. Noteworthy characteristics of the Na+-dependent glucose transport system are: 1) linear dependence of the glucose transport rate on Na+ concentration up to 0.1 M (at constant ionic strength), indicating a 1:1 stoichiometry of Na+-D-glucose cotransport under net flux conditions; 2) virtual Na+ independence of the apparent affinity of the transport system for D-glucose; 3) a stimulation-inhibition pattern if the transport rate of either substrate (D-glucose, Na+) is measured as function of increasing concentrations of its co-substrate; 4) a varying flux ratio of D-glucose to Na+ which can be either above or below 1, depending on the concentration ratio of the two substrates; 5) a rate constant for translocation of the loaded carrier which is faster than that for the dissociation of Na+. Treating Na+-D glucose co-transport analogous to an enzyme r...Continue Reading

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