Mammals, sugar transport

A brief description of sugar transport in bacteria and mammals is given principally to illustrate general principles and to outline the diversity of the processes which have evolved, particularly in mammals. The selection of material for this section is of necessity, therefore, somewhat arbitrary, and more comprehensive surveys of sugar transport may be found in several recent reviews (I, 2, 3, 4, 5, 6, 7, 8, 9,10, II, 12,13, 14). 

A.R. Walmsley, M.P. Barrett, F. Bringaud, and GW. Gould. 1998. Sugar transporters from bacteria, parasites and mammals Structure-activity relationships Trends Biochem. Sci. 23 476-480. (PubMed)... 

Walmsley, A. R., Barrett, M. P., Bringaud, P ., and Gould, Cj. W. 1998. Sugar transporters from bacteria, parasites and mammals Structure activity relationships. Trends Biochem. Sci. 23 476 480. Maes, U., Zeelen, J. R, Thanki, N.. Beaucamp, N., Alvarez. M., Thi. M H., Backmann, J., Martial, J. A., Wyns, L., Jaenicke, R., and Wierenga, R. K. 1999. Fhe crystal structure of triosephosphate iso-merase (TIM) from Ihermotogn maritima A comparative thermostability structural analysi.s of ten different TIM stmetures. Proteins 37 441-4. S3. 

Walmsiey, A.R. Barrett, M.P. Bringaud, F. Gould, G.W. Sugar Transporters from Bacteria, Parasites and Mammals Structure-activity Relationships. TIBS 1998, 23, 476-481. 

In the mammal, complex polysaccharides which are susceptible to such treatment, are hydrolyzed by successive exposure to the amylase of the saliva, the acid of the stomach, and the disaccharidases (e.g., maltase, invertase, amylase, etc.) by exposure to juices of the small intestine. The last mechanism is very important. Absorption of the resulting monosaccharides occurs primarily in the upper part of the small intestine, from which the sugars are earned to the liver by the portal system. The absorption across die intestinal mucosa occurs by a combination of active transport and diffusion. For glucose, the aclive transport mechanism appears to involve phosphorylation The details are not yet fully understood. Agents which inhibit respiration (e.g., azide, fluoracetic acid, etc.) and phosphorylation (e.g., phlorizin), and those which uncouple oxidation from phosphorylation (e.g., dinitrophenol) interfere with the absorption of glucose. See also Phosphorylation (Oxidative). Once the various monosaccharides pass dirough the mucosa, interconversion of the other... 

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