Pyruvic acid advantages

Reduction of achiral precursors is often used to produce chiral products. The advantage of this approach is that the theoretical yield of product is 100% compared to the 50% theoretical maximum for the resolution of racemates. Cross-linked crystals of lactate dehydrogenase have been used to prepare L-lactic acid from pyruvic acid in an electrolytic cell. The LDH CLCs maintained constant... 

To study the effect of polymer size on catalysis [37], pyridoxamine was linked to a series of PEIs with Mn = 600,1800,10 000, and 60 000, both simply permethylated and with additional attached dodecyl chains. The polymers were examined in the transamination of pyruvic acid and of phenylpyruvic acid, showing Michaelis-Menten behavior. The k2 and of i M determined showed only small variations with polymer size. Thus, the strong advantage of pyridoxamines attached to the Mn = 60 000 PEI, relative to simple pyridoxamine alone, was seen to almost the same extent with the smaller... 

It has been proposed that the ruminal microbial ecosystem be manipulated to improve the efficiency of converting feeds to products consumable by humans. In so doing, the organic acids may replace antibiotics and be added to feed for ruminants. Fortunately, application in ruminants is less extensive than in other farm animals and organic acids such as aspartate, citric acid, succinic acid, or pyruvic acid have been investigated and proposed as potential agents for use in ruminants. The advantages of these substances in the rumen are described as (Castillo et al., 2004) ... 

Some subaerial plants use a different pathway, involving carboxylation of phosphoenol pyruvic acid (PEP) instead of ribulose diphosphate (the C02 is actually transformed into bicarbonate before incorporation), which subsequently forms a C4 compound, oxaloacetic acid, instead of PGA (Fig. 1.7). Consequently such plants are termed C4 plants. The C4 path is a relatively recent evolutionary development of particular advantage in hot dry climates (see Box 1.10).The PEP cycle effectively transfers C02 to the Calvin cycle, and each cycle confers an isotopic fractionation. Some plants, the CAM plants (see Box 1.10), can use the combined PEP-Calvin cycle path (with some leakage of C02 out of the cell between the cycles) or just the Calvin cycle. The effects of these pathways on the overall isotopic fraction are reflected in the 813C values in Table 5.8. 

The above-mentioned chemical catalytic routes lead to racemic AHA mixtures. For the direct use of LA (or its esters) as a solvent or platform molecule for achiral molecules like acrylic acid and pyruvic acid, stereochemistry does not matter. The properties of the polyester PLA, the major application of LA, however, suffer tremendously if d and l isomers are built in irregularly [28]. This is exemplified by atactic PLA, made from racemic LA, which is an amorphous polymer with low performance and limited application. However, when l- and D-lactic acid are processed separately into their respective isotactic L- and d-PLA, as discovered by Tsuji et al., a stereocomplex is formed upon blending these polymers. This polymer exhibits enhanced mechanical and thermal properties [28, 164]. A productive route to D-Iactic acid is, however, missing today. If the chemocatalytic routes to LA are to become viable, enantiomer resolution of the racemate needs to be performed. Given separation success, a cheap source of o-lactic acid will be unlocked immediately, providing an additional advantage over the fermentation route (cfr. Table 2). 

Although advantageous for the identification of the sugars, the phenyl osazones are not applicable to the isolation of sugars. The phenylhydrazine groups are removed by treatment with benzaldehyde, concentrated hydrochloric acid, or particularly well by pyruvic acid (230), but the resulting product, a sugar osone, is a mixed ketose-aldose. 

A solution of trifluoroacetic acid in toluene was found to be advantageous for cydization of pyruvate hydrazoncs having nitro substituents[4]. p-Toluene-sulfonic acid or Amberlyst-15 in toluene has also been found to give excellent results in preparation of indole-2-carboxylale esters from pyruvate hydra-zoiies[5,6J. Acidic zeolite catalysts have been used with xylene as a solvent to convert phenylhydraziiies and ketones to indoles both in one-flask procedures and in a flow-through reactor[7]. 

OAA by pyruvate carboxylase (EC 6.4.1.1), thereby completing the net transport of the C2 unit (acetate) from the mitochondrion to the cytosol with the added advantage of having converted a reducing equivalent as NADH + H+ to NADPH + H+. This mechanism of C2 transport provides up to 50% of the NADPH + H+ for fatty acid synthesis in nonruminants. 

Although diverse in structure, most amino acids lead to a few central compounds that flow into the major metabolic pathways. All of them effectively produce pyruvate, a-ketoglutarate, oxaloacetate, succinate, fumarate, acetoacetate, or acetyl CoA (Fig. 19.6). Therefore, a large number of unusual compounds are not formed, which would require a new set of enzymatic machinery for metabolism. This is also advantageous because the carbons from degraded amino acids can be funneled into the major pathways of metabolism with normal metabolic controls. 

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