Menaquinones Menaquinone

Menaquinone Menaquinone-0 Menaquinone 4 Menaquinone K4 Menazon [78-57-9] Mendelevium Mendelevium [7 440 -11-1] Mendozite Menetrier s disease Menfegol [57821-32-6] Menhaden Menhaden oil... 

Vitamin Kp also known as vitamin Kk20)> phylloquinone or phytylmenaquinone, contains a hexahydrotetraprenyl chain (2-methyl-3-phytyl-l,4-naphthoquinone, 5-44). Phylloquinone occurs in foods of plant origin. The side chain derived from phytol has 20 carbon atoms (four isoprenoid units, of which three are reduced). The isomer with a cis-configuration in the side chain is not biologically active. The systematic name of vitamin Kj is (2 ,7 R,ll R)-2-methyl-3-(3, 7Ml, 15 -tetramethyUiexadecyl)naphtho-l,4-quinone. The second compound with the activity of vitamin K is vitamin K2 (5-45), also known as vitamin K2( ), menaquinone, menaquinone-n, MK-n or 2-methyl-3-multiprenyl-l,4-naphthoquinone (n = 0-13). The most common menaquinones contain 4-10 isoprene units, such as MK-7, additionally called pharnoquinone. Vitamin K2 is produced by many bacteria and actinomycetes. A multiprenyl side chain... 

The term vitamin K2 was applied to 2-methyl-3-difarnesyl-l,4-naphthoquinone, m.p. 54 C, isolated from putrefied fish meal. It now includes a group of related natural compounds ( menaquinones ), differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in the electron transport chain and oxidative phosphorylation. 

In contrast to vitamin K, there has been considerably more activity on fermentative approaches to vitamin (50). The biosynthetic pathway to vitamin K2 is analogous to that of vitamin except that poly(prenylpyrophosphates) are the reactive alkylating agent (51,52). Menaquinones of varying chain lengths from to have been isolated from bacteria. The most common forms are vitamin K2 35, (40) (45) significant amount of K2 20)... 

Table 2 Hsts the Recommended Dietary Allowances (RDA) for vitamin K. Although manufacture by intestinal bacteria represents a significant source of plasma menaquinone concentrations, rehance on this source alone is not sufficient to maintain healthy concentrations of menaquinone. Consequendy, dietary supplementation is necessary (76).

Phylloquinones (vitamin Kl, produced by plants) and menaquinones-n (MK-n, vitamin K2)... 

Vitamin K represents two groups of substances named phylloquinones (vitamin Kl produced by plants) and menaquinones-n (MK-n vitamin K2). Menaquinones are synthesized by bacteria, using repeated 5-carbon units in the molecules side chain, n stands for the number of 5-carbon units. Interestingly, MK-4 is synthesized only in small amounts by bacteria but can be produced by animals (including humans) from phylloquinones and is found in a number of organs. For an overview see [1, 2],... 

Membrane Signal Transduction Membrane Transport Protein Menaquinones-n Meniere s Disease Mesangial Cells... 

Rieske proteins are constituents of the be complexes that are hydro-quinone-oxidizing multisubunit membrane proteins. All be complexes, that is, bci complexes in mitochondria and bacteria, b f complexes in chloroplasts, and corresponding complexes in menaquinone-oxidizing bacteria, contain three subunits cytochrome b (cytochrome 6e in b f complexes), cytochrome Ci (cytochrome f in b(,f complexes), and the Rieske iron sulfur protein. Cytochrome 6 is a membrane protein, whereas the Rieske protein, cytochrome Ci, and cytochrome f consist of water-soluble catalytic domains that are bound to cytochrome b through a membrane anchor. In Rieske proteins, the membrane anchor can be identified as an N-terminal hydrophobic sequence (13). 

The lower redox potential in menaquinone-oxidizing be complexes can be attributed to the absence of the hydrogen bond from the Oy of Ser 163 (ISF)/Ser 130 (RFS) to the bridging sulfur S-1 (see Section III,B,2). This serine is completely conserved in Rieske proteins of bci and bef complexes, but in all sequences of Rieske proteins from menaquinone-oxidizing be complexes, alanine or glycine is found in... 

All these latter centers were seen to titrate at around 150 mV, that is, some 150 mV lower than the traditional centers, and thus form a separate subclass of this type of redox proteins (see Fig. 7). Since similar downshifts were observed for almost all redox components in the mentioned species (for a compilation, see 133), it is generally assumed that the differences between the two groups represent an adaptation to the difference in value of the quinone pool, which is plastoquinone(PQ)/ubiquinone(UQ) E 100 mV) in the traditional species and menaquinone (MK) Em,i---70 mV) in the other... 

K Phylloquinone, menaquinones Coenzyme in formation of y-carboxyglutamate in enzymes of blood clotting and bone matrix Impaired blood clotting, hemorrhagic disease... 

Figure 45-7. The vitamin K vitamers. Menadiol (or menadione) and menadiol diacetate are synthetic compounds that are converted to menaquinone in the liver and have vitamin Kactivity.

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. 

Meganathan, R., Biosynthesis of menaquinone (vitamin Kj) and ubiquinone (coenzyme Q) a perspective on enzymatic mechanism. Vitamins Hormones, 61, 173, 2001. 

Saffarini DA, SL Blumerman, KJ Mansoorabadi (2002) Role of menaquinones in Fe(III) reduction by membrane fractions of Shewanella putrefaciens. J Bacteriol 184 846-848. 

Reductase activity is located on the outer membranes of Shewanella putrefaciens and has a requirement for cytochrome c (Myers and Myers 1997) and menaquinones (Saffarini et al. 2002). 

Oxidation may take place by a modified tricarboxylic acid cycle in which the production of CO2 is coupled to the synthesis of NADPH and reduced ferredoxin, and the dehydrogenation of succinate to fumarate is coupled to the synthesis of reduced menaquinone. This pathway is used, for example, by Desulfuromonas acetoxidans and in modified form by... 

Amadi, E. N. Alderson, G. Menaquinone composition of some micrococci determined by high performance liquid chromatography. J. Appl. Bacteriol. 1991, 70, 517-521. 

Reaction centers of bacteria contain polypeptides, bacteriochlorophylls, bacteriopheo-phytins, two quinines, and nonheme iron atom. In some bacterial species, both the quinones are ubiquinones, whereas in some others one of the quinones is menaquinone [37,39]. Depending on the bacterial species chloroplasts contain plastoquinone and phyl-loquinone. Structures of ubiquinone, menaquinone, and phylloquinone are provided in Figures 7.12 through 7.14, respectively. 

All-fraws-menaquinone-4, 191, potentially useful for therapy of hypoprothrombinemia due to vitamin K deficiency, has been synthesized162 using ethyl [3-14C]acetoacetate as shown in equation 69, for drug disposition studies in animals. 

DUVOLD, T., CALI, P., BRAVO, J.-M., ROHMER, M., Incorporation of 2-C-methyl-D-erythritol, a putative isoprenoid precursor in the mevalonate-independent pathway, into ubiquinone and menaquinone of Escherichia coli, Tetrahedron Lett., 1997, 38, 6181-6184. 

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