Cells take up glucose by facilitated diffusion, via glucose transporters (GLUTs) associated with the plasma membrane, a reversible reaction (Joost and Thorens 2001). Four tissue-specific GLUT isoforms are known. Glucose in the cytosol is phosphorylated by tissue-specific kinases to yield glucose 6-phosphate, which cannot cross the plasma membrane because of its negative charge. In the liver, this reaction is catalyzed by glucokinase which has a low affinity for glucose (Km about 10 mM) but is not inhibited by glucose 6-phosphate. In other tissues, this reaction is catalyzed by isoforms of hexokinase. Hexokinases are feedback-inhibited by glucose 6-phosphate and have a high affinity for glucose (Km about 0.1 mM). Liver cells can thus accumulate large amounts of glucose 6-phosphate but only when blood glucose concentrations are high, while most other tissues can take up glucose even when blood glucose concentrations are low but cannot accumulate much intracellular glucose 6-phosphate. These differences are consistent with the view that that the liver functions to buffer blood glucose concentrations, while most other tissues take up glucose to meet immediate metabolic needs.Glucose 6-phosphatase, expressed in liver and kidney, allows glucose 6-phosphate generated by gluconeogenesis (both tissues) and glycogen breakdown (liver) to leave the cell. The absence of glucose 6-phosphatase from other tissues makes glucose uptake by these tissues essentially irreversible, consistent with the view that cells in these tissues take up glucose for local metabolic use

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G6PC , SLC37A4 , GCK , GCKR , HK1 , HK2 , HK3 , NUP88 , NUP98 , RANBP2 , SLC2A1 , SLC2A2 , SLC2A3 , SLC2A4 , TPR , NUP214 , AAAS , RAE1 , NUP155 , NUP93 , NUP58 , POM121 , NUP153 , NUP50 , NUPL2 , NUP205 , NUP210 , NUP160 , NUP188 , NUP62 , FGF21 , NUP54 , NDC1 , NUP133 , SLC50A1 , NUP107 , G6PC2 , NUP37 , NUP85 , SEH1L , SLC45A3 , G6PC3 , NUP35 , SLC2A14 , NUP43 , POM121C ,