Pyruvic acid enol, phosphate

Some sugar residues in bacterial polysaccharides are etherified with lactic acid. The biosynthesis of these involves C)-alkylation, by reaction with enol-pyruvate phosphate, to an enol ether (34) of pyruvic acid, followed by reduction to the (R) or (5) form of the lactic acid ether (35). The enol ether may also react in a different manner, giving a cyclic acetal (36) of pyruvic acid. 

From Sigma 3-aminoethylcarbazole (AEC) acrylamide/bis-acrylamide (30%) 37.5 1 amino acids alumina bentonite benzamidine bovine fiver tRNA bovine serum albumin (BSA) creatine phosphate (CP) diethyl pyrocarbonate (DEPC) dithiothreitol (DTT) Escherichia coli MRE600 tRNA pyrophosphatase (Ppase) Ca++ salt of folinic acid, (5-formyl THF) IIHPHS K salt of phospho-enol pyruvic acid, (PEP) creatine phospho kinase (CPK) protease inhibitor cocktail for fungal and yeast extracts phenylmethylsulfonyl fluoride (PMSF) spermidine trihydrochloride Tween 20. 

The enol of 2-oxopropanoic acid (pyruvic acid) is of special biological interest because the phosphate ester of this compound is, like ATP (Section 15-5F), a reservoir of chemical energy that can be utilized by coupling its hydrolysis (AG° = —13 kcal) to thermodynamically less favorable reactions ... 

In the third pathway for the formation of 3-deoxyulosonic acids, enol pyruvate phosphate and an aldose phosphate are condensed, yielding orthophosphate and a 3-deoxyulosonic acid phosphate. In addition to formation of 3-deoxy-n-araInno-heptulosonic acid 7-phosphate, another example of this type of reaction is the formation of a 3-deoxyoctulosonic acid 8-phosphate (probably 3-deoxy-D-jfJMCo-octulosonic acid) from enolp3Tmvate phosphate and D-arabinose 5-phosphate. These reactions, unlike those involving pjrruvate, proceed completely to the right and have, so far, not been reversed. 

Pyridoxal phosphate, 258 Pyruvic acid, 236 enol, phosphate, 247, 252, 261,... 

Because of the very high price of ATP, reaction (5.7) must be coupled with a regenerating system, the transfer of phosphate to ADP starting from the enol phosphate of pyruvic acid (an easily accessible and inexpensive phosphate), catalysed by the enzyme pyruvate kinase (reaction (5.8). In the same flask are mixed glucose, phosphoenolpyruvate, hexokinase, pyruvate kinase, and a catalytic quantity of ATP (about 1% mol) and the system produces D-glucose 6-phosphate until the phosphoenolpyruvate runs out. The kinases are easily accessible and, if they are immobilized on an insoluble support (see Section 10.4.1), they are reusable a certain number of times. In this way glucose 6-phosphate can be easily prepared on a 250 g scale (Poliak et al. 1977). 

Formation of starting materials for cell wall synthesis begins with two metabolic substances normally found in all life forms N-acetylglucosamine 1-phosphate and the pyrimidine nucleotide uridine triphosphate (UTP) (see Fig. 6-3). Condensation of these two compounds by elimination of pyrophosphate affords uridine-diphospho-N-acetylglucosamine (UDPNAG). Reaction with phosphoenolpyruvic acid (PEP, the activated form of the enol tautomer of pyruvic acid),5 catalyzed by a specific transferase, yields the 3-O-enolic ether. 

The enzyme-catalysed condensation of erythrose and phosphoenol pyruvate leads to 3-deoxy-(D)-arabino-heptulosonic acid 7-phosphate this loses phosphate to give an enol, which cydises to 3-dehydroquinic acid. Aromatisa-tion goes along with the loss of two molecules of water. Finally, a catechol-O-methyltransferase from S-adenosylmethionine (SAME) brings about methyla-tion of the hydroxy-function. Vanillic acid is the end-product obtained from the microorganism. 

Then, in the presence of the enzyme enolase (phosphopyruvate hydratase, EC 4.2.1.11) and as shown in Scheme 11.25, dehydration of the 2-phospho-D-glycerate (2-phosphoglycerate) occurs to produce the phosphate enol of pyruvic acid, phos-phoenolpyruvate (PEP). 

Phosphate is again present in an energy-rich form (namely the enol ester). It can be transferred by phosphopyruvate kinase to ADP this transfer affords pyruvic acid, which is the most important metabolite of both anaerobic and aerobic carbohydrate metabolism. 

The shikimic acid pathway requires the C4 sugar erythrose-4-phosphate, and phosphoenol pyruvic acid (a derivative of pyruvic acid, locked in its enol form, see Figures 1.1 and 2.19) as starting materials. The route to aromatic compounds has more steps than those met earlier, and, not surprisingly, for a plant process, uses sugar derivatives as starting materials. A total of ten carbon atoms are required, four from erythrose, and six from two molecules of pyruvate one of these is later lost as CO2. The final product therefore is a C9 compound, so that such products are... 

Transfer of the phosphoryl group to ADP in step 10 then generates ATP and gives enolpyruvate, which undergoes tautomerization to pyruvate. The reaction is catalyzed by pyruvate kinase and requires that a molecule of fructose 1,6-bis-phosphate also be present, as well as 2 equivalents of Mg2+. One Mg2+ ion coordinates to ADP, and the other increases the acidity of a water molecule necessary for protonation of the enolate ion. 

The biosynthesis of Kdo and neuraminic acid is known to involve enol-pyruvate phosphate and D-arabinose or 2-acetamido-2-deoxy-D-mannose, respectively. Nothing is known about the biosynthesis of all the other glycu-losonic acids. One interesting problem is, for example, whether the two 5,7-diamino-3,5,7,9-tetradeoxynonulosonic acids are synthesized analogously to neuraminic acid, from a three- and a six-carbon fragment, by modification of neuraminic acid on the sugar nucleotide level, or by a third, less obvious route. 

Synthetic studies for sialic acid and its modifications have extensively used the catabolic enzyme N-acetylneuraminic acid aldolase (NeuA E.C. 4.1.3.3), which catalyzes the reversible addition of pyruvate (70) to N-acetyl-D-mannosamine (ManNAc, 11) to form the parent sialic acid N-acetylneuraminic acid (NeuSNAc, 12 Scheme 2.2.5.23) [1, 2, 45]. In contrast, the N-acetylneuraminic acid synthase (NeuS E.C. 4.1.3.19) has practically been ignored, although it holds considerable synthetic potential in that the enzyme utilizes phosphoenolpyruvate (PEP, 71) as a preformed enol nucleophile from which release of inorganic phosphate during... 

This key intermediate has given its name to Nature s general route to aromatic compounds and many other related six-membeied ring compounds the shikimic acid pathway. This pathway contains some of the most interesting reactions (from a chemist s point of view) in biology. It starts with an aldol reaction between phosphoenol pyruvate as the nucleophilic enol component and the C4 sugar erythrose 4-phosphate as the electrophilic aldehyde. 

Pyruvate kinase-catalyzed removal of phosphate from PEP (128) yields the unstable intermediate enol form of pyruvate (129), presumably stabilized by metal binding (Figure 15B) . The intermediate 129 undergoes fast acid-catalyzed conversion to the keto form of pyruvate (130) (/ h+ = 1-7 x 10 s ) and can be further enhanced by... 

Finally, oxaloacetate is simultaneously decarboxylated andphosphorylated by phosphoenolpyruvate carboxykinase in the cytosol. The CO2 that vv as added to pyruvate by pyruvate carboxylase comes off in this step. Recall that, in glycolysis, the presence of a phosphoryl group traps the unstable enol isomer of pyruvate as phosphoenolpyruvate (Section 16.1.7). In gluconeogenesis, the formation of the unstable enol is driven by decarboxylation—the oxidation of the carboxylic acid to CO2 —and trapped by the addition of a phosphate to carbon 2 from GTP. The two-step pathway... 

Bromopyruvic acid inhibits S-deoxy-D-erj t ro-hexulosonate 6-phosphate aldolase " and 3-deoxy-D-ar-a6mo-heptulosonate 7-phosphate synthetase " in a similar way. The enzymes are protected from inhibition by pyruvate and phospho-enol pyruvate respectively. Since aldolases must possess a nucleophilic group to initiate the reaction, this type of inhibition should be a general property of aldolases. 

Finally, oxaloacetate is simultaneously decarboxylated and phosphorylated by phosphoenolpyruvate carboxykinase in the cytosol. The CO2 that was added to pyruvate by pyruvate carboxylase comes off in this step. Recall that, in glycolysis, the presence of a phosphoryl group traps the unstable enol isomer of pyruvate as phosphoenolpyruvate (Section 16.1.7). In gluconeogenesis, the formation of the unstable enol is driven by decarboxylation—the oxidation of the carboxylic acid to CO2—and trapped by the addition of a phosphate to carbon 2 from GTP. The two-step pathway for the formation of phosphoenolpyruvate from pyruvate has a AG° of + 0.2 kcal mol ( + 0.13 kj moP ) in contrast with +7.5 kcal mol ( + 31 kj mol ) for the reaction catalyzed by pyruvate kinase. The much more favorable AG° for the two-step pathway results from the use of a molecule of ATP to add a molecule of CO2 in the carboxylation step that can be removed to power the formation of phosphoenolpyruvate in the decarboxylation step. Decarboxylations often drive reactions otherwise highly endergonic. This metabolic motif is used in the citric acid cycle (Section IS.x.x), the pentose phosphate pathway (Section 17.x.x), and fatty acid synthesis (Section 22.x.x). 

In the first stage of peptidoglycan synthesis, UDP-N-acetylmuramic acid is synthesized, and then a pentapeptide chain becomes attached to the carboxyl group of N-acetylmuramic acid (see Scheme 2). Strom-inger found that the reaction of enolpyruvate phosphate with UDP-2-acetamido-2-deoxy-D-glucose results in the formation of a compound that appeared to be a UDP-2-acetamido-2-deoxy-D-glucose-pyruvate enol ether, and he predicted that its reduction would aflFord UDP-N-acetylmuramic acid. The occurrence of these reactions has now been confirmed, and the intermediate product has been characterized in greater detail. ... 

D. Levin and E. Racker, Condensation of arabinose 5-phosphate and phosphoryl enol pyruvate by 2-keto-3-deoxy-8-phospho5ctonic acid synthetase, / Biol. C/)cm., 234 (1959) 2532-2539 F. 

The biosynthesis of the aromatic amino acids proceeds via shikimic acid. [56] The starting point is erythrose-4-phosphate, which is produced in the Calvin cycle. The enzyme-catalysed aldol condensation with phosphoenol pyruvate leads to a heptulose, 3-deoxy-(D)-arahino-heptulonic add 7-phosphate. Elimination of phosphate produces an enol, which is converted hy a further aldol condensation into 3-dehydroquinic acid. Elimination of water and reduction then yield shikimic add. 

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