Succinate active

The P 0 ratio for the oxidation of malate and citrate is 3, whereas that for succinate is 2. At present there is detailed knowledge of only one oxidative step which can be linked with phosphate esterification, viz., oxidation of a-ketoglutarate to succinyl CoA. The succinate activation enzyme catalyzes reaction 5 of the following sequence initiated by the Kg.d. ... 

Although undoubtedly some of these enzyme units like the succinate activation enzyme can, under appropriate conditions, be resolved into two component enzymes, nonetheless the close association of the two enzymes as a single functional unit may be of great physiological importance. 

All lation. Maleic anhydride reacts with alkene and aromatic substrates having a C—H bond activated by a,P-unsaturation or an adjacent aromatic resonance (31,32) to produce the following succinic anhydride derivatives. 

As an activator of the phosphokinases, magnesium is essential in energy-requiring biological processes, such as activation of amino acids, acetate, and succinate synthesis of proteins, fats, coen2ymes, and nucleic acids generation and transmission of nerve impulses and muscle contraction (67). 

Succinic acid is absorbed from aqueous solutions by anion-exchange resins or active carbon (9—11). Succinic anhydride forms rhombic pyramidal or bipyramidal crystals. It is relatively insoluble in ether, but soluble in boiling chloroform and ethyl acetate. Succinic anhydride reacts with water and alcohols, giving the acid and monoesters, respectively. 

Succinic acid and anhydride undergo most of the reactions characteristic of dicarboxyhc acids and cycHc acid anhydrides, respectively. Other interesting reactions take place at the active methylene groups. 

Halogenation. Succinic acid and succinic anhydride react with halogens through the active methylene groups. Succinic acid heated in a closed vessel at 100°C with bromine yields 2,3-dibromosuccinic acid almost quantitatively. The yield is reduced in the presence of excess water as a result of the formation of brominated hydrocarbons. The anhydride gives the mono- or dibromo derivative, depending on the equivalents of bromine used. 

Succinic anhydride is extremely irritating to the eyes. It causes skin, mucous membranes, and respiratory tract irritation. It may be a sensiti2er. There is no evidence of carcinogenic activity in male or female tats given 50 or 100 mg/kg succinic anhydride (186) the Ames test is negative (187). LD q in rat 1510 mg/kg. There ate no estabflshed exposure limits for ACGIH TLV or TWA. 

Incineration in an approved combustion plant is the preferred method of disposal. Wastewater from succinic acid processes is suitable for biological degradation by activated sludge (188). Polymeric sorbents (189) and ferric chloride treatment processes (190) can also be used for wastes containing... 

Starch succinates [39316-70-6] are also used as thickening agents in foods. The 1-octenylsuccinate half-ester [52906-93-17, sold as its sodium salt [66829-29-6], has surface active (emulsifying) properties. 

Order of thermal stabiUty as determined by differential thermal analysis is sebacic (330°C) > a2elaic = pimelic (320°C) > suberic = adipic = glutaric (290°C) > succinic (255°C) > oxahc (200°C) > malonic (185°C) (19). This order is somewhat different than that in Table 2, and is the result of differences in test conditions. The energy of activation for decarboxylation has been estimated to be 251 kj/mol (60 kcal/mol) for higher members of the series and 126 kJ/mol (30 kcal/mol) for malonic acid (1). 

With an activated C—C triple bond two successive additions can occur if the intermediate alkene is reactive enough. DMAD and 3,5-dimethylpyrazole give an initiaj fumarate (255) which reacts further at the other end to form regioselectively the succinates (256). On the other hand, methyl ethynyl ketone reacts twice at the same carbon atom with pyrazole to form 1,1-pyrazolylbutanone (258) (68ZC458). The probable intermediate, a pyrazolide vinylogue (257), can be prepared from methyl chlorovinyl ketone and pyrazole, in a reaction which is similar to acetylation (Section 4.04.2.1.3(x)). 

KNOEVENAGEL OOEBNER STOBBE Condensation Base catalyzed aldol condensation of aldehydes or ketones with an activated methylene group of a malonic ester (Knoevenagel Doebner) or a succinic ester (Stobbe)... 

The enzyme succinate dehydrogenase (SDH) is competitively inhibited by malo-nate. Figure 14.14 shows the structures of succinate and malonate. The structural similarity between them is obvious and is the basis of malonate s ability to mimic succinate and bind at the active site of SDH. However, unlike succinate, which is oxidized by SDH to form fumarate, malonate cannot lose two hydrogens consequently, it is unreactive. 

In 1932 Krebs was studying the rates of oxidation of small organic acids by kidney and liver tissue. Only a few substances were active in these experiments —notably succinate, fumarate, acetate, malate, and citrate (Figure 20.2). Later it was found that oxaloacetate could be made from pyruvate in such tissues, and that it could be further oxidized like the other dicarboxylic acids. 

The mechanism of succinyl-CoA synthetase is postulated to involve displacement of CoA by phosphate, forming succinyl phosphate at the active site, followed by transfer of the phosphoryl group to an active-site histidine (making a phosphohistidine intermediate) and release of succinate. The phosphoryl moiety is then transferred to GDP to form GTP (Figure 20.13). This sequence of steps preserves the energy of the thioester bond of succinyl-CoA in a series of high-energy intermediates that lead to a molecule of ATP ... 

The pronounced influence of the phenyl group on optical activity led Fredga and Palm" to initiate an investigation on the optical activity of thiophene derivatives, in order to use this physical property for the elucidation of the aromatic character of thiophene. 2-(27) and 3-Thenylsuccinic acid (28), 2- (29) and 3-thienyl-succinic acid (30), 2- (31) and 3-thienylglycolic acid (32), 2-(33) and 3-a-methoxythienylacetie acid (34), -phenyl 2-thienyl-glycolic acid (35), -(2-thienyl)-y5-phenylpropionic acid (36), a-phenyl- -(2-thienyl) propionic acid (37), a,/ -di (2-thienyl)propionic acid (38) have been resolved into antipodes with the help of optically active bases. 

Figure 4. The citrate cycle. There is complete oxidation of one molecule of acetyl-CoA for each turn of the cycle CH3COSC0A + 2O2 - 2CO2 + H2O + CoASH. The rate of the citrate cycle is determined by many factors including the ADP/ATP ratio, NAD7NADH ratio, and substrate concentrations. During muscle contraction, Ca is released from cellular stores (mainly the sarcoplasmic reticulum) and then taken up in part by the mitochondria (see Table 2). Ca " activates 2-oxoglutarate and isocitrate dehydrogenases (Brown, 1992). Succinate dehydrogenase may be effectively irreversible. Enzymes ...

Van Der Laarse, W.J., LSnnergren, J., Diegenbach, P.C. (1991). Resistance to fatigue of single muscle fibers from Xenopus related to succinate dehydrogenase and myofibrillar ATPase activities. Exp. Physiol. 76, 589-596. 

Figure 11. (a) Succinate dehydrogenase activity in normal skeletal muscle, (b) Muscle from patient with complex 11 deficiency showing severely decreased succinate dehydrogenase activity. 

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