Resumo

BERMUDEZ, Valmore et al. Biología molecular de los transportadores de glucosa: clasificación, estructura y distribución. AVFT [online]. 2007, vol.26, n.2, pp.76-86. ISSN 0798-0264.

Hexoses like glucose, galactose and fructose serve as basic fuel molecules for eucaryotic cells. These molecules are unable to diffuse across cellular membranes, and require transporter proteins for entry into and exit from cells. Three distinct groups of hexose transporters have been identified and classified based on their dependence on cellular energy and its chemistry structure. Each of the transporters has different affinities for glucose and the other hexoses, which largely dictates their function. The hexose transporters are large integral membrane proteins. Based on the deduced amino acid sequences of their cloned cDNAs, they have similar structures, consisting of 12 or 14 membrane-spanning regions with cytoplasmic C-terminal and N-terminal tails. Also, they all appear to be glycosylated on one of the extracellular loops. Transport of sugars across membranes appears to result from a series of conformational changes which "flips" the transporter between alternate states with the substrate binding site either facing the extracellular or cytoplasmic side of the membrane. Transport in either direction is thus possible, depending on relative substrate concentrations on either side of the membrane. The original protein, GLUT1, was identified in molecular term’s 12 years ago. In the subsequent 15 years, a family of related transporters was identified (GLUTs 1-14). The impact of these discoveries is better realized when we list a sample of the processes that utilize different members of the GLUT family: control of glycemia; insulin dependent glucose utilization; transport pathways in brain neurons and glia; mechanisms of glucose and fructose uptake in the intestinal track; reabsorption of glucose in kidney tubules and jejunum; maturation of transporters during lactation and weaning; sensing of glucose levels by the pancreas and the liver; control of glucose uptake in high fat feeding; glucose uptake in response to exercise, adaptive response of energy metabolism to cellular stress.

Palavras-chave : Glut; Glucose; transporter; facilitative diffusion; SGLT-1; SGLT-2; Co-transporter.

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