Sugar transport, active

Fig. 4.5.2 Actual strategies for CDG diagnosis. Initial investigations on CDG patients are routinely carried out by isoelectric focusing (IEF) of serum transferrin. With a CDG type I pattern, subsequent analysis should imply determination of phosphomannomutase (PMM) and phos-phomannose isomerase (PMI) activities. Further studies, like analysis of the lipid-linked- and protein-bound-oligosaccharides, determination of enzyme or sugar transporter activities and molecular biology studies often have to be performed in more specialised laboratories. HPLC High-performance liquid chromatography, TLC thin-layer chromatography...

Table 1. Summary of nucleotide sugar transport activities identified in Golgi- and ER fractions and genes that have been isolated so far.

Mechanisms of active and passive transport in a family of homologous sugar transporters found in both prokaryotes and eukaryotes... 

Yeasts contain a large number of different active and passive sugar-transport systems. The first of these to be cloned was the glucose-repressible, high-affinity passive glucose transporter of Saccharomyces cerevisiae, which is encoded by the SNF3 gene... 

The galactose, arabinose and xylose transporters of E. coli The bacterium E. coli possesses at least 7 proton-linked, active transport systems for sugars (for a recent review see [212]). Three of these transporters, which catalyze the uptake of L-arabinose, D-xylose and D-galactose by symport with protons, are related in sequence to the sugar transporters discussed above. They probably represent the best-characterized of the non-mammalian transporters, and so are discussed here in some detail. 

Doege, H., et al. Activity and genomic organization of human glucose transporter 9 (GLUT9), a novel member of the family of sugar-transport facilitators predominantly expressed in brain and leucocytes. Biochem. J. 2000, 350, 771-776. 

Van Deenen and colleagues have shown (Biochim. Biophys. Acta 406, 169, 1975) that the activity of a phospholipase against phosphatidylcholine liposomes has a sharp temperature maximum at the phase transition temperature. In addition, Linden et al. (Proc. Natl. Acad. Sci. US 70, 2271, 1973) showed a marked temperature dependence of sugar transport into E. Coli fatty acid auxotrophs at the temperature corresponding to the onset of phase separations of the lipids. 

The predominant active sugar transport systems of intestine and kidney are specific for sugars which have the pyranose structure with a... 

However, if these limitations are remembered, it can be instructive to compare the patterns of interaction which have been variously reported for substrates and inhibitors of mutarotase, with similar patterns for the kidney and intestinal sugar transport processes. In Table XIII the reported specificities for mammalian intestine are compared. In cases where comparative data are available, all sugars which are actively transported or which are passively transported but share the same carrier as glucose also interact with the active center of mutarotase. Particularly interesting is the observation that L-fucose, the most potent sugar inhibi-... 

LeFevre, P. G., Sugar Transport in the Red Blood Cell Structure-Activity... 

Bihler, I., Intestinal Sugar Transport. Ionic Activation and Chemical... 

Figure 1 Examples of several bacterial membrane proteins. The outer membrane (OM) of Gram-negative bacteria contains exclusively fS-barrel proteins, and three examples are shown BtuB (PDB ID 1NQF), which is the 22 p-stranded TonB-dependent active transporter for vitamin B 2/ th LamB or maltoporin trimer (PDB ID 1AF6), which is the 18 p-stranded passive sugar transporter and OmpA (PDB ID 1BXW), which is an 8 p-stranded protein that provides structural support for the OM. Proteins in the cytoplasmic membrane (CM) are helical, and three examples are shown the potassium channel KcsA (PDB ID 1BL8), which is a tetramer Sec YEG (PDB ID 1RH5), which forms the protein transport channel in Methanococcus and BtuCD (PDB ID ...

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)... 

A. Kleinzeller, The specificity of the active sugar transport in kidney cortex cells, Biochim. Biophys. Acta, 211 264-276 (1970),... 

---