Quinones biosynthesis

The shikimate pathway is the major route in the biosynthesis of ubiquinone, menaquinone, phyloquinone, plastoquinone, and various colored naphthoquinones. The early steps of this process are common with the steps involved in the biosynthesis of phenols, flavonoids, and aromatic amino acids. Shikimic acid is formed in several steps from precursors of carbohydrate metabolism. The key intermediate in quinone biosynthesis via the shikimate pathway is the chorismate. In the case of ubiquinones, the chorismate is converted to para-hydoxybenzoate and then, depending on the organism, the process continues with prenylation, decarboxylation, three hydroxy-lations, and three methylation steps. - ... 

The third pathway involved in the quinones biosynthesis is the isoprenoid route. This pathway is primarily important for the formation of prenyl side chains of prenylquinones (ubiquinone, menaquinone, plastoquinones, etc.). The side chains of ubiquinones and prenylated naphthoquinones derive from polyprenyl diphosphates. 

Ramamoorthi R, ME Lidstrom (1995) Transcriptional analysis of pqqD and study of the regulation of pyrroloquinoline quinone biosynthesis in Methylobacterium extorquens AMI. J Bacteriol Yll 206-211. 

Kolkmann, R. and E. Leistner, 4-(2 -Carboxyphenyl)-4-oxobu-tyryl coenzyme A ester, an intermediate in vitamin K2 (mena-quinone) biosynthesis, Z. Naturforsch., 42c, 1207-1214 (1987). 

Tyrosine monooxygenase, 4-hydroxy-phenylpyruvate dioxygenase, homogentisate prenylase (D 22, D 22.4) Further enzymes of plastid quinone biosynthesis Plastid quinones,... 

Typical examples are experiments in which COg was administered to intact leaves in competition with mevalonic acid in the location of the site of plastid quinone biosynthesis and experiments with Penicillium cyclopium, where the channeling of the precursor L-phenylalanine and its incorporation into the alkaloids of the cyclopenin-viridicatin group and proteins were studied... 

Quinones form an important component of the electron-transport system in plants and mammals. Ubiquinol, the reduced form of coenzyme Qio, and menaquinone (vitamin K) have significant antioxidant properties, playing a major role in protecting cells from free-radical damage (Cadenas and Hochstein 1992). Any of four different metabolic pathways may be involved in quinone biosynthesis (Harborne and Baxter 1993). The largest subgroup are the anthraquinones, which occur mainly as glycosides and are referred to in Chapter 4. 

Yang XP, Zhong GF, Lin JP, Mao DB, Wei DZ (2010) PyrroloquinoUne quinone biosynthesis in Escherichia coli through expression of the Gluconobacter oxydans pqqABCDE gene cluster. J Ind Microbiol Biotechnol 37 575-580... 

Shestopalov AI, Bogachev AV, Murtazina RA, Viryasov MB, Skulachev VP (1997) Aeration-dependent changes in composition of the quinone pool in Escherichia coli. Evidence of post-transcriptional regulation of the quinone biosynthesis. FEBS Lett 404 272-274 Shults CW, Oakes D, Kieburtz K, Beal MF, Haas R, Plumb S, Juncos JL, Nutt J, Shoulson I, Carter J, KompoUti K, Perlmutter JS, Reich S, Stem M, Watts RL, Kurlan R, Molho E, Harrison M, Lew M (2002) Effects of coenzyme QIO in early Parkinson disease evidence of slowing of the functional decline. Arch Neurol 59 1541-1550... 

The first examples of macrocyclization by enyne RCM were used in Shair s impressive biomimetic total synthesis of the cytotoxic marine natural product longithorone A (429) [180]. This unique compound features an unusual hep-tacyclic structure which, in addition to the stereogenic centers in rings A-E, is also chiral by atropisomerism arising from hindered rotation of quinone ring G through macrocycle F (Scheme 85). It was assumed that biosynthesis of 429 could occur via an intermolecular Diels-Alder reaction between [12]paracy-... 

Since carotenoids are derived for the central isoprenoid pathway (Fig. 13.3), the regulation of their formation must involve a co-ordinated flux of isoprenoid imits into this branch of the pathway as well as into others such as the biosynthesis of sterols, gibberellins, phytol and terpenoid quinones. An imderstanding of the complexities of regulation of the pathway is necessary in order to target the regulatory steps for genetic manipulation. 

Quinones represent a very large and heterogeneous class of biomolecules. Three major biosynthetic pathways contribute to the formations of various quinones. The aromatic skeletons of quinones can be synthesized by the polyketide pathway and by the shikimate pathway. The isoprenoid pathways are involved in the biosynthesis of the prenyl chain and in the formation of some benzoquinones and naphthoquinones. ... 

Quinone methides have been shown to be important intermediates in chemical synthesis,1 2 in lignin biosynthesis,3 and in the activity of antitumor and antibiotic agents.4 They react with many biologically relevant nucleophiles including alcohols,1 thiols,5-7 nucleic acids,8-10 proteins,6 11 and phosphodiesters.12 The reaction of nucleophiles with ortho- and /iara-quinone methides is pH dependent and can occur via either acid-catalyzed or uncatalyzed pathways.13-17 The electron transfer chemistry that is typical of the related quinones does not appear to play a role in the nucleophilic reactivity of QMs.18... 

Despite the importance of the oxidative polymerization of 5,6-dihydroxyin-dole, in the biosynthesis of pigments, little experimental data are known on the oxidation chemistry of the oligomers of 1. For such reasons, three major dimers of 1, such as 2-4 (Scheme 2.9), have been computationally investigated at PBEO/ 6-31+G(d,p) level of theory both in gas and in aqueous solution (by PCM solvation model) to clarify the quinone methide/o-quinone tautomeric distribution. 

Polyphenoloxidase (PPO, EC 1.14.18.1) is one of the most studied oxidative enzymes because it is involved in the biosynthesis of melanins in animals and in the browning of plants. The enzyme seems to be almost universally distributed in animals, plants, fungi, and bacteria (Sanchez-Ferrer and others 1995) and catalyzes two different reactions in which molecular oxygen is involved the o-hydroxylation of monophenols to o-diphenols (monophenolase activity) and the subsequent oxidation of 0-diphenols to o-quinones (diphenolase activity). Several studies have reported that this enzyme is involved in the degradation of natural phenols with complex structures, such as anthocyanins in strawberries and flavanols present in tea leaves. Several polyphenols... 

Nucleophilic catalysts, 10 420 Nucleophibc reagents, 10 389 Nucleophibc substitution in benzene, 3 601 in 1,2-dichloroethane, 6 255 in fullerenes, 12 248 of quinones, 21 261—262 during pulp bleaching, 21 35-38 Nucleosomes, 17 611-612, 613 Nucleotide biosynthesis inhibitors,... 

Luibrand RT, Erdman TR, Vollmer JJ, Scheuer PJ, Finer J, Clardy J (1979) Ilimaquinone a sesquit-erpenoid quinone from a marine sponge (Hippospongia metachromia).Tetrahedron 35 609-612 Moore BS (2005) Biosynthesis of marine natural products microorganisms (Part A). Nat Prod Rep 22 580-593... 

The molecular target site of triketone herbicides is the enzyme -hydroxyphenylpyruvate dioxygenase (HPPD). Inhibition of this enzyme disrupts the biosynthesis of carotenoids and causes a bleaching (loss of chlorophyll) effect on the foliage similar to that observed with inhibitors ofphytoene desaturase (e.g. norflurazon). However, the mechanism of action of HPPD inhibitors is different. Inhibtion of HPPD stops the synthesis of homogen tisate (HGA), which is a key precursor of the 8 different tocochromanols (tocopherols and tocotrienols) and prenyl quinones. In the absence of prenylquinone plastoquinone, phytoene desaturase activity is interrupted. The bleaching of the green tissues ensues as if these compounds inhibited phytoene desaturase. 

An interesting variation on the above theme for the biosynthesis of the pavines and isopavines has been proposed by Dyke (169). This proceeds via a quinone methine intermediate. The precursor, a l-benzyltetrahydroisoquinoline-3-car-boxylic acid 165 oxidizes to a quinone methide 166, which then decarboxylates to afford a reactive enamine 167. Cyclization then readily furnishes a pavine. Alternatively, hydration of the enamine 167 at C-4 would ultimately result in formation of an isopavine (Scheme 36). 

In normal individuals phytonadione and the menaquinones have no activity while in vitamin K deficiency the vitamin promotes the hepatic biosynthesis of factor II (prothrombin), factor VII, factor IX and factor X. Vitamin K functions as an essential cofactor for the enzymatic activation of precursors of these vitamin K dependent clotting factors. The quinone structure of the active form of vitamin K, i.e. reduced vitamin K or hydroquinone. 

Menaquinone. The incorporation of [2- C]mevalonate and [2- C]-2-methyl-l,4-naphthoquinone into MK-4, normally considered a bacterial quinone, has been demonstrated in marine invertebrates such as crabs and starfish." Incorporation into 2,3-epoxy-MK-4 (163) was also observed. Cell-free extracts have been prepared from Escherichia coli which catalyse the conversion of o-succinylbenzoic acid (164) into l,4-dihydroxy-2-naphthoic acid (165) and menaquinones. In the presence of farnesyl pyrophosphate the major menaquinone produced was MK-3. Genetic studies with mutants of E. coli K12 that require (164) offer support for the generally accepted pathway for MK biosynthesis via (164) and (165)." The enzyme system that catalyses the attachment of the polyprenyl side-chain to 1,4-dihydroxy-2-naphthoic acid to form demethylmenaquinone-9 (166) has been isolated from E. colU ... 

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