Glucose transporters roles

Bakris GL, Fonseca VA, Sharma K, Wright EM. Renal sodium-glucose transport role in diabetes mellitus and potential clinical implications. Kidney Int 2009 75(12) 1272-7. 

Glucose entry into most cells is concentration driven and independent of sodium. Four glucose transporters (GLUT) are listed in Table 1-12-1. They have different afiinities for glucose coinciding with their respective physiologic roles. Normal glucose concentration in peripheral blood is 4-8 mM (70-140 m dL). 

Before glycolysis from glucose can begin, glucose has to be transported into the ceU. This is achieved by a transporter protein, in the plasma membrane (Chapter 5). There are five different types of glucose transporter, all encoded by separate genes. The proteins have slightly different properties, different tissue distribution and somewhat different roles in these tissues. Their roles are briefly described in Table 6.1. A sixth transporter is specific for fructose it is... 

Although the rate of glucose transport can regulate the flux through glycolysis, as indicated above, several enzymes also play a role. 

Day, A.J. et al.. Absorption of quercetin-3-glucoside and quercetin-4 -glucoside in the rat small intestine the role of lactase phlorizin hydrolase and the sodium-dependent glucose transporter, Biochem. Pharmacol., 65, 1199, 2003. 

Okada, T. Kawano, Y Sakakibara, T. Hazeki, O. Ui, M. Essential role of phosphatidylinositol 3-kinase in insulin-induced glucose transport and antilipolysis in rat adipocytes. Studies with a selective inhibitor wortmannin. J. Biol. Chem., 269, 3568-3573 (1994)... 

That is, the cotransporter can pump glucose inward until its concentration within the epithelial cell is about 9,000 times that in the intestine. As glucose is pumped from the intestine into the epithelial cell at the apical surface, it is simultaneously moved from the cell into the blood by passive transport through a glucose transporter (GLUT2) in the basal surface (Fig. 11-44). The crucial role of Na+ in symport and antiport systems such as these requires the continued outward pumping of Na+ to maintain the transmembrane Na+ gradient. 

One of the most important effects of insulin is to increase glucose uptake by cells 373/389 The mechanism is thought to depend upon the transporter protein GLUT4, which is stored within the membranes of small cytoplasmic vesicles. Binding of insulin to its receptors induces movement of these vesicles to the plasma membrane where fusion with the plasma membrane makes the GLUT4 molecules available for glucose transport.390 Phosphatidylinositol 3-kinase also plays an important role. The PtdIns(3,4)P2 and PtdIns(3,4,5)P3 generated by this enzyme (Fig. 11-9)... 

Role of Membrane Glucose Transport, Arch. Biochem. Biophys. (1970) 138, 493. 

Possible roles for hydrolytic and synthetic activities of the enzyme in glucose transport have been considered in Section II,D. 

Expression, Regulation, and Functional Role of Glucose Transporters (GLUTs) in Brain... 

Glycosylation has also been reported to improve intestinal absorption of peptide drugs which demonstrate poor membrane penetrability. For instance, glycosylation at the /V-terminus of tetrapeptide (Gly-Gly-Tyr-Arg) increases its resistance to degradation by peptidases in addition, Na+-dependent glucose transporters were shown to play an important role in the intestinal absorption of both /)-(succinylamido)phenyl a- or p-D-ghicopyranosides (Nomoto et al. 1998). 

Parker, C., Barnell, W. O., Snoep, J. L., Ingram, L. O., and Conway, T. 1995. Characterization of the Zymomonas mobilis glucose facilitator gene product (gif) in recombinant Escherichia colt examination of the transport mechanism, kinetics and the role of glucokinase in glucose transport. Mol. Microbiol., 15, 759-802. 

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