Phosphate 6-tocopherol

FIGURE 8.18 Dolichol phosphate is an initiation point for the synthesis of carbohydrate polymers in animals. The analogous alcohol in bacterial systems, undecaprenol, also known as bactoprenol, consists of 11 isoprene units. Undecaprenyl phosphate delivers sugars from the cytoplasm for the synthesis of cell wall components such as peptidoglycans, lipopolysaccharides, and glycoproteins. Polyprenyl compounds also serve as the side chains of vitamin K, the ubiquinones, plastoquinones, and tocopherols (such as vitamin E). 

The strong Bronstedt acid nature of some hexacoordinated phosphorus derivatives, [7",H ] (Et20)4 in particular, was recently used within the context of an industrial application [36]. The conjugated acid of tris(oxalato)phosphate anion 7 was found to effectively catalyze the ring-forming reaction of trimethyl-hydroquinone 63 with isophytol 64 to give (all rac)-a-tocopherol 65 (ethylene-carbonate/heptane 1 1,100 °C, 90%, Scheme 19). This process is particularly... 

A reduction and activation of HjOj by other one-electron donors, like semiquinones, has also to be considered. This follows from a study of the ethylene production from methionine in the presence of pyridoxal phosphate, a reaction characteristic for OH radicals or for Fenton-type oxidants. The ethylene production in the presence of dioxygen, anthraquinone-2-sulfonate, and an NADPH-generating system in phosphate buffer pH 7.6 was inhibited by SOD and by catalase, but stimulated by scavengers of OH radicals, like 0.1 mM mannitol, a-tocopherol, and formiate... 

Aromatic compounds arise in several ways. The major mute utilized by autotrophic organisms for synthesis of the aromatic amino acids, quinones, and tocopherols is the shikimate pathway. As outlined here, it starts with the glycolysis intermediate phosphoenolpyruvate (PEP) and erythrose 4-phosphate, a metabolite from the pentose phosphate pathway. Phenylalanine, tyrosine, and tryptophan are not only used for protein synthesis but are converted into a broad range of hormones, chromophores, alkaloids, and structural materials. In plants phenylalanine is deaminated to cinnamate which yields hundreds of secondary products. In another pathway ribose 5-phosphate is converted to pyrimidine and purine nucleotides and also to flavins, folates, molybdopterin, and many other pterin derivatives. 

Active analogues and related compounds include dl-a-Tocopherol l-a-toccpherol esters (succinate, acetate, phosphate), and fi, (. c.-tocopherol-,. The principal physiological forms are D-a-tocopherol. tocopheronolactone, and their phosphate esters. 

Zondlo Fiume, M., Final report on the safety assessment of tocopherol, tocopheryl acetate, tocopheryl linoleate, tocopheryl linoleate/oleate, tocopheryl nicotinate, tocopheryl succinate, dioleyl tocopheryl methylsilanol, potassium ascorbyl tocopheryl phosphate, and tocophersolan, Int. J. Toxicol., 21 (suppl 3), 51,2002. 

Kotegawa, M., Sugiyama M., Shoji, T., Haramaki N., Orgura, R. (1993). Effect of a-tocopherol on high energy phosphate metabolite levels in rat heart hy P-NMR using a Langendorff perfusion technique. J. Mol. Cell Cardiol. 25 1067-74. 

Figure 11 Biosynthesis of isoprenoid type cofactors. 18, Heme a 39, pyridoxal 5 -phosphate 43, 1-deoxy-D-xylulose 5-phosphate 46, thiamine pyrophosphate 83, acetyl-CoA 84, (S)-3-hydroxy-3-methylglutaryl-CoA 85, mevalonate 86, isopentenyl diphosphate (IPP) 87, dimethylallyl diphosphate (DMAPP) 88, pyruvate 89, D-glyceraldehyde 3-phosphate 90, 2C-methyl-D-erythritol 4-phosphate 91, 2C-methyl-erythritol 2,4-cyclodiphosphate 92, 1-hydroxy-2-methyl-2-( )-butenyl 4-diphosphate 93, polyprenyl diphosphate 94, cholecalciferol 95, fS-carotene 96, retinol 97, ubiquinone 98, menaquinone 99, a-tocopherol.

Fig. 4 Color stability of PP processed in presence of 300 ppm tocopherol in combination with the phosphate U-622. Total amount of products formed from tocopherol is also shown.

KEY WORDS aerobic respiration, 300 glycerol phosphate shuttle, 316 protonmotive force, 307 a-tocopherol, 326... 

Quinones are firmly established in photosynthesis models. But how about vitamins E and K How do quinones work in animals First of all they transport electrons in a similar way as in photosynthesis (Metzler, 1977 Voet, 1990). Second, tocopherol is known to act as an antioxidant or radical quencher. The radical chain starting with the decomposition of unsaturated lipid peroxides, for example, is inhibited by tocopherol, which produces long-lived semiquinone radicals (Scheme 7.2.10). Vitamin E prevents, for example, sterility in rats fed rancid lipids. Vitamin E in connection with carotenes is also used as a stabilizer for diet margarines containing large amounts of essential fatty acids. Another possible activity of tocopherol is participation in oxidative phosphorylation a hydroquinone is mono-esterified with phosphoric acid to form a quinol phosphate and then oxidized to the quinone. The cationic quinone-phosphate adduct then reacts with anionic phosphate to form pyrophosphate (Scheme 7.2.10), (Wang, 1969 Breslow, 1980 Isler and Brubacher, 1982). 

Figure 12.2 Hypothetical cellular signaling by tocopheryl phosphate (TP). The tocopherols become phosphorylated in the membrane by a kinase. Proteins containing a tocopheryl phosphate binding domain (TP-domain) may translocate to TP in the membrane and become activated or inactivated. A phosphatase would inactivate the cellular signaling by removing the phosphate group.

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