Fumarate, from succinate

Analogous to the formation of fumarate from succinate catalyzed by succinate dehydrogenase, a flavoenzyme, ethylene can be produced by the following sequence of reactions ... 

Complex II is perhaps better known by its other name—succinate dehydrogenase, the only TCA cycle enzyme that is an integral membrane protein in the inner mitochondrial membrane. This enzyme has a mass of approximately 100 to 140 kD and is composed of four subunits two Fe-S proteins of masses 70 kD and 27 kD, and two other peptides of masses 15 kD and 13 kD. Also known as flavoprotein 2 (FP2), it contains an FAD covalently bound to a histidine residue (see Figure 20.15), and three Fe-S centers a 4Fe-4S cluster, a 3Fe-4S cluster, and a 2Fe-2S cluster. When succinate is converted to fumarate in the TCA cycle, concomitant reduction of bound FAD to FADHg occurs in succinate dehydrogenase. This FADHg transfers its electrons immediately to Fe-S centers, which pass them on to UQ. Electron flow from succinate to UQ,... 

Oxidation of Succinate to Fumarate The succinate formed from succinyl-CoA is oxidized to fumarate by the flavoprotein succinate dehydrogenase ... 

Mitochondria from adult H. diminuta exhibit an NADH-coupled fumarate reductase (Table 5.11). This presents a potential dilemma with respect to the utilisation of intramitochondrial reducing equivalents by this worm. As reducing equivalents are generated by the malic enzyme in the form of NADP, a mechanism for the transfer of hydride ions from NADPH to NAD to produce NADH is required so that electron-transport-associated activities can proceed and terminate with the reduction of fumarate to succinate. Such a mechanism does exist in H. diminuta as there is a non-energy-linked, membrane-associated transhydrogenase (214, 217, 221, 476). This transhydrogenase, which also occurs in H. microstoma (216) and Spirometra mansonoides (220) catalyses the reaction ... 

Fig. 5.12. Gas chromatogram of TMS derivatives of organic acids. Peaks 1 = lactic 2 = (3-hydroxy-butyric 3 = fumaric 4 = succinic 5 = malic 6 = oxaloacetic 7 = a-ketoglutaric 8 = citric 9 = iso-citric acid. Conditions glass column, 12 ft. X 4 mm, 5% OV-22 on Gas-Chrom P (80-100 mesh) nitrogen flow-rate, 40-50 ml/min temperature programme, 2°C/min from 50°C. (Reproduced from Anal. Lett., 1 (1968) 713, by courtesy of M.G. Horning and Marcel Dekker.)...

Fig. 9a4) between cyclopentadiene and a C=C bond of the dumbbell-shaped part of the rotaxane. The dumbbell-shaped part contains two dicarbonyl stations (Fig. 9a3), one derived from fumaric acid (tram -CO-C H=CH-CO-. station 1), the other derived from succinic acid (—CO-CH2-CH2-CO-, station 2). The two diamide sites of the macrocycle can form four H-bonds with the two carbonyl groups of a given station (Fig. 9al for the interaction of the two carbonyl groups of fumaric-acid-derived station 1 with the four NH groups of the macrocycle through four H-bonds, see Fig. 9a2). Station 1 (derived from fumaric acid) has a tram C=C double bond due to its preorganization, this station interacts with the macrocycle better than the station 2. Consequently, the macrocycle is initially located at station 1 (Fig. 9a5). The Diels-Alder cycloaddition (80° C, 90% yield) of cyclopentadiene to the double bond of station 1 results in a mixture of diastereomers (Fig. 9a4) and causes displacement of the macrocycle from station 1 to station 2 (Fig. 9a6). The cycloaddition is reversible and the retro-Diels-Alder reaction occurs quantitatively (250°C, reduced pressure) when cyclopentadiene dissociates from the axle of the rotaxane this produces a displacement of the macrocycle from station 2 back to station 1. 

COs to form oxalacetate which under anaerobic conditions is reduced to malate. The malate in turn may be converted to fumarate and succinate (Fig, 5). The last step in this series of reactions is blocked by malonate. The second pathway involves the aerobic condensation of pyruvate and oxalacetate followed by oxidation of the condensation product to form -ketoglutarate and succinate. Wood has proposed that the first condensation product of the aerobic tricarboxylic cycle is cfs-aconitic acid which is then converted to succinate by way of isocitric, oxalosuccinic, and a-ketoglutaric acids. The a-ketoglutarate is decarboxylated and oxidized to succinic acid. Isotopic a-ketoglutarate containing isotopic carbon only in the carboxyl group located a to the carbonyl would be expected to yield non-isotopic succinate after decarboxylation. This accounts for the absence of isotopic carbon in succinate isolated from malonate-poisoned liver after incubation with pyruvate and isotopic bicarbonate. 

Maleic Acid HOOC—CH = CH—COOH Fumaric Acid S3mthesis from Succinic Acid.—Two isomeric acids are known oi the constitution of di-carboxy ethene, or bulen-di-oic acid. They are named maleic acid and fumaric acid. Their synthesis from succinic acid establishes their constitution. Mono-brom succinic acid when... 

German name, Trauben-saure, is derived from the word for grapes. It is probable that it does not exist in grapes as racemic acid but that it is formed from the dextro acid as this transformation can easily be effected by the action of acids or even by water alone. When tartaric acid is prepared synthetically from succinic acid, from glyoxal, or from malic, maleic or fumaric acids either racemic acid or meso-tartaric acid is always formed. That is, synthetic reactions result in the formation of an inactive form. The methods of splitting racemic acid into its optically active components has been fully discussed. The sodium-ammonium racemate is the only salt that is of importance. This has been spoken of in connection with the method of splitting racemic acid into its components.. Like the free acid this salt exists, in dilute solution, as equal molecular parts of the dextro and levo forms. Only in concentrated solution does it exist as the racemate itself. 

Besides non-enzymatic 02 generation. Of can be enzymatically formed as a result of the ApH+-consuming reverse electron transfer from succinate to O2. In fact, standard redox potential of fumarate/succinate is slightly positive whereas that of OfOf is negative. It was found that ApH+ generated by succinate oxidation via Complexes III and IV can be used to reduce O2 to 02 (eq. 4) ... 

Succinate is oxidized to fumarate. Two hydrogens are removed together with their electrons from succinate and transferred to FAD, forming FADH2. 

A sufficient separation of all these compounds, therefore, is only achieved by using two AS4 columns in series. However, the separation of the two stereoisomers, maleic acid and fumaric acid, is much easier. It is obtained under standard conditions and is shown in Fig. 3-87. In contrast to monocarboxylic acids, the retention of aliphatic dicarboxylic acids increases with decreasing pK value. The corresponding data are summarized in Table 3-20. This finding is explained by the charge-stabilizing effect exerted by the +1-effect of the methylene groups which decreases from succinic acid to oxalic acid ... 

Battat et al. [87] used A. flavus ATCC 13697 as the biocatalyst for the production of malic acid from glucose in a 16-1 stirred-tank fermentor. The optimal fermentation conditions are as follows agitation rate, 350 rpm Fe +, 12 mg/1 nitrogen (as ammonium sulfate), 271 mg/1 phosphate, 1.5 mM. Total amount of CaCOj added was 90 g/1. Fermentation was carried out at 32 °C for up to 200 h. Under the aforementioned conditions, 113 g/1 of L-malic acid were produced from 120 g/1 glucose utilized with an overall productivity of 0.59 g/l/h. Based on the molar yield, it was 128% for mahc acid and 155% for total acid (malic, fumaric and succinic acid). The increase in acid accumulation during the course of incubation coincides with the increase in the activities of NAD -malate dehydrogenase, fumarase and citrate synthase. 

Because of the importance of organic acids, resulting from organic matter decomposition and from the root exudates on the solubility of trace elements in the rhizosphere (Mench and Martin, 1991), it was demonstrated that LMMOLs have the ability to desorb Cd from soils, with malate, fumarate, and succinate being the most effective (Krishnamurti et al., 1997 Naidu and Harter, 1998) (Table 5.7). 

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