Sugar transporters glucose

FIGURE 10.26 Glucose transport in E. coli is mediated by the PEP-dependent phosphotransferase system. Enzyme I is phosphorylated in the first step by PEP. Successive phosphoryl transfers to HPr and Enzyme III in Steps 2 and 3 are followed by transport and phosphorylation of glucose. Enzyme II is the sugar transport channel. 

Wood IS, Trayhurn P (2003) Glucose transporters (GLUT and SGLT) expanded families of sugar transport proteins. BrJNutr 89 3-9... 

Transport systems can be described in a functional sense according to the number of molecules moved and the direction of movement (Figure 41-10) or according to whether movement is toward or away from equilibrium. A uniport system moves one type of molecule bidirectionally. In cotransport systems, the transfer of one solute depends upon the stoichiometric simultaneous or sequential transfer of another solute. A symport moves these solutes in the same direction. Examples are the proton-sugar transporter in bacteria and the Na+ -sugar transporters (for glucose and certain other sugars) and Na -amino acid transporters in mammalian cells. Antiport systems move two molecules in opposite directions (eg, Na in and Ca out). 

Yeasts contain a large number of different active and passive sugar-transport systems. The first of these to be cloned was the glucose-repressible, high-affinity passive glucose transporter of Saccharomyces cerevisiae, which is encoded by the SNF3 gene... 

Fig. 5. A speculative model for the arrangement of the helical regions of the sugar transporters in the membrane. The helices are numbered as shown in Fig. 4. The small circle labelled s represents a glucose molecule.

In summary, studies on the human erythrocyte glucose transporter and other members of a large family of prokaryotic and eukaryotic sugar transporters have yielded... 

The sugar transporters are specific for D-forms of glucose, galactose and fine-... 

Doege, H., et al. Activity and genomic organization of human glucose transporter 9 (GLUT9), a novel member of the family of sugar-transport facilitators predominantly expressed in brain and leucocytes. Biochem. J. 2000, 350, 771-776. 

Doege, H., et al. GLUT8, a novel member of the sugar transport facilitator family with glucose transport... 

Wu, X., et al. Cloning and characterization of glucose transporter 11, a novel sugar transporter that is alternatively spliced in various tissues. Mol. Genet. Metab. 2002, 76, 37—45. 

However, if these limitations are remembered, it can be instructive to compare the patterns of interaction which have been variously reported for substrates and inhibitors of mutarotase, with similar patterns for the kidney and intestinal sugar transport processes. In Table XIII the reported specificities for mammalian intestine are compared. In cases where comparative data are available, all sugars which are actively transported or which are passively transported but share the same carrier as glucose also interact with the active center of mutarotase. Particularly interesting is the observation that L-fucose, the most potent sugar inhibi-... 

If the tissue locations of mutarotase were extracellular, it would be possible to speculate on a role for the enzyme in the transport of sugar via these water-transporting capillary spaces. We are presently attempting to develop fluorescent antibody to the enzyme to use in visualizing the location of the enzyme in tissues which transport glucose. 

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