Glycerate pathway

Dicarboxylic add cyda a cyclic pathway (Fig.) which enables the utilization of glyoxylic acid or one of its precursors (e.g. glycolic acid) as a carbohydrate source for the growth of microorganisms. The D.c.a. includes some of the reactions of the tricarboxylic add cycle. It also involves malate synthase (EC 4.1.3.2 see Glyoxylate cycle). If the concentration of D.c. a. interm iates is too severely reduced by diversion to synthetic pathways, they can be replenished from the Glycerate pathway (see). 

Metabolic cycle a catalytic series of reactions in which the product of one bimolecular reaction is regenerated A-tB->->—>C + A. Thus A acts catalyti-cally, is required only in small amounts, and can be considered as a carrier of B.The catalytic function of A and other members of the M.c. insure economic conversion of B into C. B is the substrate of the M.c. and C is the product. If intermediates are withdrawn from the M.c., e.g. for biosynthesis, the stationary concentrations of the M.c. intermediates must be maintained by synthesis. Replenishment of depleted M.c. intermediates is called anaplerosis. Only one anaplerotic reaction is necessary, since the resulting intermediate is in equilibrium with all other members of the cycle. Anaplerosis may be served by a single reaction, which converts a common metabolite into an intermediate of the M.c. (e.g. pyruvate to oxalo-acetate in the tricarboxylic acid cycle), or it may involve a metabolic sequence of reactions, i. e. an anaplerotic sequence (e.g. the glycerate pathway which provides phosphoenofpyruvate for anaplerosis of the dicarboxylic acid cycle). 

In the presence of Au/C catalyst, the reaction pathway was studied concluding that glycerate/tartronate amounts represents the probe of path a and glycolate of path b [41c] (Scheme 1). The overall selectivity of the reaction is dictated by the balance of path a and b and represents the most valuable parameter to be considered for evaluating the effectiveness of a catalyst. 

Deficiencies of enzymes involved in glycolysis, the hexose monophosphate pathway, the closely related glutathione metabolism and synthesis, and nucleotide metabolism have emerged as causes of hereditary nonspherocytic hemolytic anemias (Table 1) (F10, Fll, M27). Some enzyme deficiencies, such as diphospho-glycerate mutase deficiency, lactate dehydrogenase deficiency, and NADH cy-... 

The CPPase substrate DMAPP (15) is formed from isopentenyl pyrophosphate (IPP) (14) via the IPP isomerase reaction. It had been assumed that IPP was generated only via mevalonic acid (12) (Fig. 2), but Rohmer discovered another route, 2-C-methyl-D-erythritol 4-phosphate (13) (MEP) pathway (Fig. 2) [22, 23]. A key step in the MEP pathway is the reaction catalyzed by 1-deoxy-D-xylulose 5-phosphate synthase (DXS), which combines hydroxyethyl thiamine pyrophosphate (hydroxyethyl TPP) generated from pyruvic acid (17) and TPP with glyceral-dehyde 3-phosphate (18) to yield 1-deoxy-D-xylulose 5-phosphate (19) containing five carbons. The mevalonate pathway operates in the cytosol of plants and animals, whereas the MEP pathway is present in the plastid of plants or in eubacteria [24-27]. 

There is some evidence that one potential effect of the release of fluoride is for it to act as an antimicrobial agent. It is known that millimolar concentrations of fluoride ion in water will affect a variety of activities in several types of cell [38]. It does this by denaturing the enzymes. In bacteria, the most important enzyme which can be affected is enolase, and this is responsible for the conversion of 2-P-glycerate to 2-enol pyruvate in the glycolic pathway. Enolase is a magnesium-containing... 

Although we have described metabolic transformations in plant cells in terms of individual pathways, these pathways interconnect so completely that we should instead consider pools of metabolic intermediates shared among these pathways and connected by readily reversible reactions (Fig. 20-37). One such metabolite pool includes the hexose phosphates glucose 1-phosphate, glucose 6-phosphate, and fructose 6-phosphate a second includes the 5-phosphates of the pentoses ri-bose, ribulose, and xylulose a third includes the triose phosphates dihydroxyacetone phosphate and glycer-aldehyde 3-phosphate. Metabolite fluxes through these... 

OOC-CHOH-CHO. The latter is then dehydrogenated to D-glycerate. Write out a detailed scheme for the dicarboxylate cycle. Also indicate how glucose and other cell constituents can be formed from intermediates created in this biosynthetic pathway. 

Except for glycerate-l,3-bisphosphate all of the intermediates in the pathway are pictured as belonging to one of three metabolic pools. Within each metabolic pool the intermediates are readily interconvertible and usually present in relative concentrations close to their equilibrium values. Between the pools the concentrations of the intermediates can be very different because of the lack of rapid intercon-... 

Inspection of the amino acid biosynthetic pathways shows that all amino acids arise from a few intermediates in the central metabolic pathways (see fig. 21.1). Amino acids de-rived from a common intermediate are said to be in the same family. For example, the serine family of amino acids, which includes serine, glycine, and cysteine, all arise from glycerate-3-phosphate (see fig. 21.1). The carbon flow from the central metabolic pathways to amino acids is a regulated... 

As shown in Scheme 3.4, there are several reaction pathways of glycerol oxidation to form dihydroxyacetone, glyceric acid, hydroxypyruvic acid, mesoxalic acid, and so on. Dihydroxyacetone is formed by the oxidation of a secondary hydroxy group under... 

The lipid messenger OEA links dietary fat intake to satiety. CellMetab. 8, 281-288. Simon, G. M., and Cravatt, B. F. (2006). Endocannabinoid biosynthesis proceeding through glycer-ophospho-jV-acyl ethanolamine and a role for alpha /beta-hydrolase 4 in this pathway. J. Biol. 

Fig. 8.2 Glycolysis and related pathways. Glycolysis is a central metabolic machinery in which one mole of glucose is catabolized to two moles of pyruvate, NADH, and ATP. Under aerobic conditions, pyruvate is further oxidized by mitochondrial system. In erythrocytes DHAP is a dead-end product however, in brain it can be converted into direction of lipid synthesis. Glycolysis and the pentose phosphate pathway (pentosePP) are interconnected via fructose-6-P and glyceral-dehyde-3-P. A high level of NADPH favors lipid synthesis via pentose phosphate shunt (pentosePP). At TPI inhibition (TPI deficiency), glyceraldehyde-3-Pcan be produced via G6PDH as well, to contribute to the glycolytic flux. a-GDH catalyzes the...

Enzymatic Reaction Mechanisms II Biochemical reactions often look more complex than they really are. In the pentose phosphate pathway (Chapter 14), sedoheptulose 7-phosphate and glycer-aldehyde 3-phosphate react to form erythrose 4-phosphate and fructose 6-phosphate in a reaction catalyzed by transaldolase. 

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