Blood Lewis enzyme

Like lacNAc termini, type-1 structures may be fucosylated by a2-FucT and a4-FucT (Lewis enzyme, FucT III) to yield the H-type-1 and the Lewis structures, respectively [24, 81]. In turn the H-type-1 structure can be converted into a Lewis, or a blood group A or B active compound, by the action of a4-FucT, and blood group A- (a3-GalNAcT) or B-enzyme (a3-GalT), respectively [24, 81]. Alternatively, type-1 structures can be disialylated by the concerted action of a a3-NeuAcT and a a6-NeuAcT to yield the terminal NeuAc(a2-3)Gal(pi-3)[NeuAc(o2-6)]-GlcNAc structure [111, 112],... 

Exposure. Concentrations of cyanide and its metabolite thiocyanate can be measured in the blood, urine, and tissues. Since certain amounts of cyanide can always be found in the human tissues, urine, and expired air, only exposure to high doses can be detected by this way. Cyanide is metabolized in the body to thiocyanate in a reaction that is catalyzed by an enzyme rhodanese and mercaptopyruvate sulfur transferase (Ansell and Lewis 1970). 

FIGURE 1.15 A synthetic Lewis blood group deteiminant/ceramide antigen (45) and the synthetic specific enzyme inhibitor immucillin H (46). 

A number of non-natural fucosyl donors have also been probed with this enzyme [89]. As can be seen from Fig. 12, the C-6-atom of fucose is open for modifications. L-Gal and o-Ara are good substrates, whereas replacement of the 2-OH group of the fucose donor apparently is not tolerated by FucT VI. Indeed, Hindsgaul and coworkers succeeded in attaching the blood group A trisaccharide to the 6-position of the fucose donor and proved the biocatalytic transfer of this strange sugar [90]. The combination of non-natural donors with non-natural acceptors by enzymatic fucosyltransfer has also been probed which proved to be instrumental in the assembly of a library of sialyl-Lewis tetrasaccharides (Fig. 12) [91]. 

In studies of lymph from injured and noninjured limbs, Lewis (L6) found that after 60°C bums applied to the hind limb of the anesthetized cat the remained intracellular. Even after burning at 80°C there was only a small increase of K+ in the lymph, and this could be accounted for by the hemolysis which occurred and which resulted in a slight rise in blood as a direct result of cell damage. It may be that the release of is associated with changes which also affect mitochondrial enzymes. It is only after massive cell breakdown as caused by freezing the limb solid that considerable amounts of K+ appear in the lymph drainage. 

FIGURE 6.6 Biotransformation and liver structure. Liver cells called hepatocytes are wedged between blood channels (sinusoids) and bile canals. Foreign chemicals that have been taken up into the bloodstream diffuse down their eoncentration gradients out of the bloodstream and into hepatocytes. There they are subject to biotransformation by Phase I and Phase II enzymes. The structurally transformed chemicals move out of the hepatocyte, entering either the blood sinusoid (smaller chemicals) or the bile canal (larger chemicals) or both (chemicals of intermediate size). Biotransformed chemicals that enter the bloodstream are eliminated by the kidneys. Biotransformed chemicals that enter the bile canals are eliminated in the feces. (Reprinted with permission from David Shier, Jackie Butler and Ricki Lewis, Hole s Human Anatomy and Physiology, 7th ed. [Dubuque Wm. C. Brown, 1996], 696.)... 

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