Any protein that transports glucose. In mammals they are a family of twelve-transmembrane integral transporters. GLUT1 is ubiquitously expressed with particularly high levels in erythrocytes and in the endothelial cells in the brain. GLUT2 is a low-affinity transporter present in liver, intestine, kidney, and pancreatic beta cells. GLUT3 is expressed primarily in neurons and GLUT1 in conjunction with GLUT3 allows glucose to cross the blood–brain barrier and enter neurons. The GLUT4 isoform is the major insulin-responsive transporter, predominantly restricted to striated muscle and adipose tissue. Defects in GLUT-4 may be associated with some forms of diabetes. GLUT5 is a fructose transporter, expressed in insulin-sensitive tissues (skeletal muscle and adipocytes) of humans and rodents. High-fructose diets lead to up-regulation of the transporter. GLUT6 is a pseudogene on chromosome 5. GLUTX1 appears to be important in early blastocyst development.
Subjects: Medicine and Health — Chemistry.