Methyl succinate, succinic dehydrogenase

Methylnaphthoquinone, see Menadione Methyl succinate, succinate dehydrogenase and, 237-238 Methyl viologen... 

Some bioactive flavones include aldose reductase inhibitors (apigenin 4 -methyl ether (acacetin), apigenin 7-0-apioside (apiin), 5,7-dihydroxyflavone (chrysin) and luteolin) antiinflammatory 5-LOX inhibitors (5,6,7-trihydroxyflavone (baicalein), 5,6,3, 4 -tetrahydroxy 7-methoxyflavone (pedalitin), 5,3, 4 -trihydroxy 6,7-dimethoxyflavone (cirsiliol, 6-0-methylpedalitin) and flavone) a COX inhibitor (flavone) iodothyronine deiodinase inhibitors (acacetin, chrysin and luteolin) a NADH and succinate dehydrogenase inhibitor (luteolin) millet-derived, goitrogenic inhibitors of thyroid peroxidase (flavone C-glycosides orientin and vitexin) and protein kinase inhibitors (acacetin, apigenin, baicalein, flavone, luteolin, 5,7,3, 4, 5 -pentahydroxyflavone (tricetin) and tricetin 3, 4, 5 -trimethyl ether). 

According to Veeger et al. 149), succinate dehydrogenase can also oxidize L-chlorosuccinate, L-methyl succinate, D-malate, and L-malate. Brodie and Nicholls 174) have reported that monofluorosuccinate and... 

Aconitate dehydratase, succinate dehydrogenase, and fumarase yield stereospecific products. Labeling experiments with in methyl and carboxyl carbons of acetyl-CoA or in all of the carbons of oxaloacetate yield the following results in terms of the intermediates or product formed. 

Retey et al. (72) used this same principle in their work on the stereochemistry of citrate formation from chiral acetyl-CoA with Si-citrate synthase (Scheme 15). The chiral methyl group was converted into one of the methylene groups of succinate and the distinction between sets (I, 2, 3) and (4, 5, 6) was then based on the known different isotope effects for the removal of pro-/ ( hMd = 5.3 kH/kT = 12) vs. pro-5 (kH/kD = 1.35 kH/kj = 1.5) hydrogens of succinate in the succinate dehydrogenase reaction (73). However, the malate synthase/fumarase procedure is clearly the most commonly used method to analyze the configuration and chiral purity of chiral methyl groups. 

Nitric oxide donors [sodium nitroprusside, S-nitroso-N-acetyl-D,L-penicillamine or l-hydroxy-2-oxo-3-(N-methyl-6-aminohexyl)-3-methyl-l-triazene = NOC-9] did not affect the activities of non-specific alkaline phosphatase and non-specific esterase in rat and mouse kidney proximal tubulo-cytes which do not contain nitric oxide synthase I (Dahrmann etal. 1997). However, the activities of succinate dehydrogenase (EC 1.3.99.1), cytochrome c oxidase (EC 1.9.3.1), catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), and cholinesterase (EC 3.1.1.7) and different types of adenosine triphosphatase (EC 3.6.1.3) were found reduced. 

In succinate dehydrogenase, FAD is covalently bound to its enzyme as a result of a base removing a proton from the C-8 methyl group and an acid donating a proton to N-1. Then a histidine side chain of the enzyme adds to the methylene carhon at C-8 as a proton adds to N-5. Draw the mechanism for these two steps. 

FIG. 4.2 Malate metabolism in mitochondria from body wall muscle of adult Ascaris smm. (1) Fumarase (2) malic enzyme (3) pyruvate dehydrogenase complex (4) complex I (5) succinate-coenzyme Q reductase (complex II, fumarate reductase) (6) acyl CoA transferase (7) methylmalonyl CoA mutase (8) methyl-malonyl CoA decarboxylase (9) propionyl CoA condensing enzyme (10) 2-methyl acetoacetyl CoA reductase (11) 2-methyl-3-oxo-acyl CoA hydratase (12) electron-transfer flavoprotein (13) 2-methyl branched-chain enoyl CoA reductase (14) acyl CoA transferase. 

So, the biosynthesis of methionine (Met, M), the first of the essential amino adds to be considered (Scheme 12.13), begins by the conversion of aspartate (Asp, D) to aspartate semialdehyde in the same way glutamate (Glu, E) was converted to glutamate semialdehyde (vide supra. Scheme 12.6). Phosphorylation on the terminal carboxylate of aspartate (Asp, D) by ATP in the presence of aspartate kinase (EC 2.7.2.4) and subsequent reduction of the aspart-4 yl phosphate by NADPH in the presence of aspartate semialdehyde dehydrogenase (EC 1.2.1.11) yields the aspartate semialdehyde. The aspartate semialdehyde is further reduced to homoserine (homoserine oxoreductase, EC 1.1.1.3) and the latter is succinylated by succinyl-CoA with the liberation of coenzyme A (CoA-SH) in the presence of homoserine O-succinyl-transferase (EC 2.3.1.46). Then, reaction with cysteine (Cys, C) in the presence of cystathionine y-synthase (EC 2.5.1.48) produces cystathionine and succinate. In the presence of the pyridoxal phosphate protein cystathionine P-lyase (EC 4.4.1.8), both ammonia and pyruvate are lost from cystathionine and homocysteine is produced. Finally, methylation on sulfur to generate methionine (Met, M) occurs by the donation of the methyl from 5-methyltetrahydrofolate in the presence of methonine synthase (EC 2.1.1.13). 

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