Thiamine diphosphate

Some simple bacteria, such as those that produce yoghurt, reduce the pyruvic acid to lactic acid, and the reaction stops there, without much of 

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Aldehydes and ketones are converted into alkenes by means of a nucleophilic addition called the Wittig reaction. The reaction has no direct biological counterpart but is important both because of its wide use in the laboratory and drug manufacture and because of its mechanistic similarity to reactions of the coenzyme thiamin diphosphate, which well see in Section 29.6. 

Stepl of Figure 29.11 Addition of Thiamin Diphosphate The conversion of pyruvate to acetyl CoA begins by reaction of pyruvate with thiamin diphosphate, a derivative of vitamin B(. Formerly called thiamin pyrophosphate, thiamin diphosphate is usually abbreviated as TPP. The spelling thiamine is also correct and frequently used. 

O Nucleophilic addition of thiamin diphosphate (TPP) ylide to pyruvate gives an alcohol addition product. 

Elimination of thiamin diphosphate ylide from the hemithioacetal intermediate yields acetyl dihydrolipoamide. .. 

Step 4 of Figure 29.11 Elimination of Thiamin Diphosphate The product of the HETPP reaction with lipoamide is a hemithioacetal, which eliminates thiamin diphosphate vlide. This elimination is the reverse of the ketone addition in step 1 and generates acetyl dihydrolipoamide. 

Step 4 of Figure 29.12 Oxidative Decarboxylation The transformation of cr-ketoglutarate to succinyl CoA in step 4 is a multistep process just like the transformation of pyruvate to acetyl CoA that we saw in Figure 29.11. In both cases, an -keto acid loses C02 and is oxidized to a thioester in a series of steps catalyzed by a multienzynie dehydrogenase complex. As in the conversion of pyruvate to acetyl CoA, the reaction involves an initial nucleophilic addition reaction to a-ketoglutarate by thiamin diphosphate vlide, followed by decarboxylation, reaction with lipoamide, elimination of TPP vlide, and finally a transesterification of the dihydrolipoamide thioester with coenzyme A. 

Thiamin, structure of, 530, 1045 thiazolium ring in, 530 Thiamin diphosphate, p/Ca of, 1151 reaction with pyruvate, 1151-1153 structure of. 1151 ylide from. 1151 Thiazole, basicity of. 948 thio-, thioester name ending, 787 Thioacetal, synthesis of, 743 Thioanisole, electrostatic potential map of. 777... 

Fig. 32 shows a stepwise separation of broad zones of thiamine mono- and diphosphate on a CS-KU-2 cellosorbent. The dynamic criteria (A and A.) predict the zones limited by sharp boundaries with a complete yield of the components at pH 4.9 for thiamine diphosphate and at pH 6.5 for thiamine monophosphate. It is noteworthy that the criterion A predetermines the slow motion ot the thiamine... 

Fig. 32. Stepwise preparative desorption chromatography of phosphoric esters of thiamine on CS-KU-2 cellosorbent /) highly phosphoric thiamine esters, 2) thiamine diphosphate, 3) thiamine monophosphate, 4) thiamine, 5) impurities...

Biosynthesis of Thiamine Diphosphate from Thiazole and Pyrimidine... 

Thiamine is present in cells as the free form 1, as the diphosphate 2, and as the diphosphate of the hydroxyethyl derivative 3 (Scheme 1) in variable ratio. The component heterocyclic moieties, 4-amino-5-hydroxymethyl-2-methylpyrimidine (4) and 4-methyl-5-(2-hydroxyethyl)thiazole (5) are also presented in Scheme 1, with the atom numbering. This numbering follows the rules of nomenclature of heterocyclic compounds for the ring atoms, and is arbitrary for the substituents. To avoid the use of acronyms, compound 5 is termed as the thiazole of thiamine or more simply the thiazole. This does not raise any ambiguity because unsubstituted thiazole is encountered in this chapter. Other thiazoles are named after the rules of heterocyclic nomenclature. Pyrimidine 4 is called pyramine, a well established name in the field. A detailed account of the present status of knowledge on the biosynthesis of thiamine diphosphate from its heterocyclic moieties can be found in a review by the authors.1 This report provides only the minimal information necessary for understanding the main part of this chapter (Scheme 2). 

Thiamine was biosynthesized by resting cells of S. typhimurium strain thilO/T-ath-383, which can synthesize thiamine from exogenous glucose, AIRs, and thiazole.54 Derepression was achieved by conventional means. The organism was cultivated in the presence of a suboptimal amount of thiamine (20 nM), the washed cells were resuspended in a minimal medium containing glucose (10 mM), thiazole (1-2 mM), and labeled AIRs (10 p,M). During the incubation (1.5 hours 37°C), the level of thiamine diphosphate in the cells had risen from about 0.04 to 0.5 nmol/mg. In work with molecules labeled with stable isotopes, thiamine was extracted and cleaved by ethanethiol to 4-amino-5-(ethyl-... 

Thiamine diphosphate, biosynthesis, from thiazole and pyrimidine precursors, 269-271... 

This thermodynamic driving force is particularly useful tvith multienzyme equilibrium systems such as that used in the gram-scale synthesis of tv ro equivalents ofo-xylulose 5-phosphate (104) from (26) (Figure 10.38) [171,172]. Similarly, the corresponding 1-deoxy-D-xylulose 5-phosphate tvas efficiently produced from pyruvate and (34) by the catalytic action of the thiamine diphosphate-dependent 1-deoxy-D-xylulose 5-phosphate synthase (DXS) (EC 2.2.1.7) from E. coli [173]. 

Other thiamine diphosphate-dependent enzymes have recently been scrutinized for their preparative value [166]. Although pyruvate decarboxylase (PDC) (EC 4.1.1.1)... 

Figure 10.40 Stereocomplementary acyloin syntheses based on the carboligation capacity of thiamine diphosphate-dependent enzymes.

Figure 17-5. Oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex. Lipoic acid is joined by an amide link to a lysine residue of the transacetylase component of the enzyme complex. It forms a long flexible arm, allowing the lipoic acid prosthetic group to rotate sequentially between the active sites of each of the enzymes of the complex. (NAD nicotinamide adenine dinucleotide FAD, flavin adenine dinucleotide TDP, thiamin diphosphate.)...

Pyruvate is oxidized to acetyl-GoA by a multienzyme complex, pyruvate dehydrogenase, that is dependent on the vitamin cofactor thiamin diphosphate. 

Thiamin has a central role in energy-yielding metabo-hsm, and especially the metabohsm of carbohydrate (Figure 45-9). Thiamin diphosphate is the coenzyme for three multi-enzyme complexes that catalyze oxidative decarboxylation reactions pymvate dehydrogenase in carbohydrate metabolism a-ketoglutarate dehydro-... 

Figure45-9. Thiamin, thiamin diphosphate, and the carbanion form.

Thiamin deficiency can result in three distinct syndromes a chronic peripheral neuritis, beriberi, which may or may not be associated with heart ilure and edema acute pernicious (fulminating) beriberi (shoshin beriberi), in which heart failure and metabolic abnormalities predominate, without peripheral neuritis and Wernicke s encephalopathy with KorsakofPs psychosis, which is associated especially with alcohol and dmg abuse. The central role of thiamin diphosphate in... 

The activation of apo-transketolase(the enzyme protein) in erythrocyte lysate by thiamin diphosphate added in vitro has become the accepted index of thiamin nutritional status. 

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