Carbohydrates & Uptake

in mammals

Carbohydrate uptake in the body involves the absorption and transport of monosaccharides.

In the small intestine, glucose and galactose are taken up by the Sodium-Glucose Transport Protein (SGLT1) through active carrier transport, while fructose is taken up by facilitated diffusion through Glucose transporter (GLUT) 5 (GLUT5).

Once inside the enterocyte, all three monosaccharides are transported out into the capillary through Glucose transporter 2 (GLUT2), and then transported to the liver via the portal vein.

At the liver, galactose and fructose are completely taken up through GLUT5, while only 30-40% of glucose is taken up through Glucose transporter 2 (GLUT2).

in bacteria

In bacteria such as Escherichia coli, carbohydrate uptake involves the phosphoenolpyruvate-dependent phosphotransferase system (PTS), which is responsible for transporting more than 20 carbohydrates into the bacterial cell.

The PEP (2-phosphoenolpyruvate) Group Translocation / Phosphotransferase System (PTS) consists of energy-coupling proteins and carbohydrate-specific enzymes that catalyze carbohydrate translocation and phosphorylation.

The phosphorylation status of PTS components reflects the availability of carbohydrates and the energy conditions of the cell, and it plays a role in catabolite repression, inducer control, and chemotaxis
Kornberg 1976 J Cell Physiol. 89(4): 545-9
Kotrba et al. 2001 J Biosci Bioeng. 92(6): 502-17

see also:
Escherichia coli (E. coli)