Glyceric acid synthesis

Table 1. Asymmetric synthesis of (R)-a-Substituted Glyceric Acids, (R)-4.

The sugar rearrangement system together with the glycolytic enzymes that convert glucose 6-P to glycer-aldehyde 3-P can function to transform hexose phosphates into pentose phosphates (Fig. 17-8B Eq. 17-16) which may be utilized for nucleic acid synthesis in erythrocytes and other cells.130 131... 

D-Mannitol has a diverse range of industrial applications. It is a nonhydroscopic, low-calorie, noncariogenic sweetener utilized by the food industry as well as a feedstock for the synthesis of other compounds. For example, mannitol can be oxidized at the 3 or 4 position to form two molecules of glyceraldehyde or glyceric acid, which can be used as building blocks for other compounds (Heinen et al., 2001 Makkee et al., 1985 van Bekkum and Verraest, 1996). Mannitol is formed from inulin via hydrolysis followed by catalytic hydrogenation. This yields mannitol and sorbitol from which the mannitol can be readily crystallized (Fuchs, 1987). Currently mannitol is primarily synthesized from starch. 

D. Serine is synthesized from glucose. The pathway branches from glycolysis at phospho-glyceric acid, which is reduced, transaminated, and dephosphoiylated by phosphoserine phosphatase. Pyruvate kinase is a glycolytic enzyme that functions beyond the branch point for serine synthesis. 

Location. Plant fatty acid synthesis appears to be limited to chloroplasts. A chloroplast isozyme of pyruvate dehyrogenase catalyzes the conversion of pyruvate to acetyl-CoA. Pyruvate is also derived from glycerate-3-phosphate, an intermediate in the Calvin cycle, a biosynthetic pathway in which plants incorporate COz into sugar molecules. (The Calvin cycle is discussed in Chapter 13.)... 

The lower-carbon, phosphorylated sugars, so important in biochemical processes, also came in for the further attention of Fischer and Ballou. New methods of synthesis were worked out for 2-0-phospho-o-glyceric acid, D-glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, and (with Dr. MacDonald) the enantiomorphous erythrose 4-phosphates. The suspected biochemical importance of the n-erythrose 4-phosphate was then quickly established when Srinivasan, Katagiri, and Sprinson of Columbia University demonstrated its condensation with 0-phospho-enolpyruvic acid to 5-dehydroshikimic acid by Escherichia coli. 

In the rat, the synthesis of D-glyceric add seems to be connected with that of L-ascorbic acid administration of chloretone increases the urinary elimination of both acids (cf. Article by W. E. Knox and M. N. D. Goswami, Section 3.4, this volume). o-Glyceric acid is not, however, a direct precursor of L-ascorbic add, and Isherwood et al. (13) state that the connection between these two acids may lie only in that both require some common enzyme or coenzyme system. 

Many plant tissues contain hydroxypyruvate reductase (o-glycerate dehydrogenase) but it is especially active in leaves (Stafford et al., 1954 Stafford and Magaldi, 1954). Tolbert et al. (1970) purified the spinach enzyme and investigated its properties. It catalyzes reduction of hydroxypyruvate to D-glyceric acid by NADH [Eq. (3)]. Although the equilibrium is toward glyceric acid rather than hydroxypyruvate, the presence of sufficient amino donor and an appropriate transaminase would allow serine synthesis by the nonphosphorylated pathway with Eq. (3) as an intermediate step. 

Dihydroxiacetone (tanning agent,building block in oi anic synthesis) Glyceric acid (building block in organic synthesis)... 

New information on this problem has come from enzyme studies and isotope tracer studies. The work discussed in the preceding section disclosed that a great many different products were synthesized from carbon dioxide during photosynthesis. The nearest approach to a first product of photosynthesis is n-glyceric acid 3-phosphate. From this compound, through a whole series of enzyme-catalyzed reactions, the plant carries out the synthesis of the carbohydrates. 

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