Flavin mononucleotide 5-phosphate

Riboflavin-5 -Phosphate. Riboflavin-5 -phosphate [146-17-8] (vitamin B2 phosphate, flavin mononucleotide, FMN, cytoflav), C2yH22N402P,... 

Riboflavin, or vitamin B2, is a constituent and precursor of both riboflavin 5 -phosphate, also known as flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). The name riboflavin is a synthesis of the names for the molecule s component parts, ribitol and flavin. The structures of riboflavin. 

All NOS isoforms utilize L-arginine as the substrate, and molecular oxygen and reduced nicotinamide adenine dinucleotide phosphate (NADPH) as cosubstrates. Flavin adenine dinucleotide (FMN), flavin mononucleotide (FAD), and (6R)-5,6,7,8-tetrahydro-L-biopterin (BH4) are cofactors of the enzyme. All NOS isoforms contain heme and bind calmodulin. In nNOS and eNOS,... 

The varions flavin phosphates and their acetyl derivatives were identified by pH titration, electrophoresis, and H-NMR, which permit direct analysis of crude reaction prodncts as well as rapid purity check of commercial flavin mononucleotide or riboflavin 5 -monophosphate (FMN or 5 -FMN) [7]. Riboflavin 4 -monophosphate was determined as the main by-product of commercial FMN by preparative TLC on cellulose with n-butanol/acetic add/water (5 2 3, v/v) as a solvent [7]. 

The second type of biological electron transfer involves a variety of small molecules, both organic and inorganic. Examples of these are (a) nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) as two electron carriers and (b) quinones and flavin mononucleotide (FMN), which may transfer one or two electrons. The structure of NAD and its reduced counterpart NADH are shown in Figure 1.12. 

HPLC with fluorescence detection was employed for the analysis of riboflavin (RF), flavin mononucleotide (FMN) and flavin-adenin dinucleotide (FAD) in beer, wine and other beverages. The investigation was motivated by the finding that these compounds are responsible for the so-called taste of light which develops in beverages exposed to light. Samples were filtered and injected in to the analytical column without any other pretreatment. Separations were carried out in an ODS column (200 X 2.1mm i.d. particle size 5 pm). Solvents A and B were 0.05 M phosphate buffer (pH 3) and ACN, respectively. The... 

The term NOS is used to denote a family of three related but distinct isoenzymes neuronal NOS (nNOS) endothelial NOS (eNOS, endothelium and platelets) and inducible NOS (iNOS, endothelium, vascular smooth muscle and macrophage). In addition to reduced nicotinamide adenine dinucleotide phosphate (NADPH) shown in Figure 5.5, NOS enzymes also require flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN) and tetrahydrobiopterin (BH4) as coenzymes. 

Physiologic electron acceptors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) produced similar effects on cathodic hydrogen evolution from mild steel as achieved with methyl viologen (Bryant and Laishley 1990). These experimental results showed that the mild steel rods reacting with phosphate can preferential act as electron donors for the reduction of low-potential electron carriers. All hydrogenases catalyze a reversible reaction for the formation and oxidation of hydrogen, which requires low-potential electron carriers for the enzyme activity (Church et al. 1988 Fauque et al. 1988). 

In addition to the catalysts listed in Table 2, several rhodium(I) complexes of the various diphosphines prepared by acylation of bis(2-diphenylphosphinoethyl)amine were used for the hydrogenation of unsaturated acids as well as for that of pyruvic acid, aUyl alcohol and flavin mononucleotide [59,60]. Reactions were mn in 0.1 M phosphate buffer (pH = 7.0) at 25 °C under 2.5 bar H2 pressure. Initial rates were in the range of 1.6-200 mol H2/molRh.h. 

Figure 9.6 Sequence of electron carriers in the electron transfer chain. The positions of entry into the chain from metabolism of glucose, glutamine, fatty acyl-CoA, glycerol 3-phosphate and others that are oxidised by the Krebs cycle are shown. The chain is usually considered to start with NADH and finish with cytochrome oxidase. FMN is flavin mononucleotide FAD is flavin adenine dinucleotide.

Ochoa reported that malic enzyme from L. plantarum was NAD and not NADP specific. The malic enzyme of cauliflower bud mitochondria (31) is NAD and NADP specific, with NAD being the preferred cofactor. Both the malo-lactic activity and NADH producing activity of the Leuconostoc oenos system (6,7, 8) was strictly NAD specific. Nicotinamide-adenine dinucleotide phosphate, flavin adenine dinucleotide, and flavin mononucleotide could not substitute in either of these activities. 

The metal complexes of riboflavin-5 -phosphate (flavin mononucleotide, FMN) have been studied. Zn(FMN)-2H20 shows some perturbation of the IR bands of the phosphate group, suggesting that metal binding occurs at the phosphate group.579 Reviews are available.9-15 468c h 1470... 

In 1989, BH4 was found to be a cofactor for nitric oxide synthase (NOS) [ 126, 127]. BH4 is also involved in dimerization of NOS, as NOS is catalytically active in a homodimer structure. Three isoforms of NOS exist neuronal NOS (NOS 1), inducible NOS (NOS 2) and endothelial NOS (NOS 3). BH4 is essential for all NOS isoforms. The NOS isoforms share approximately 50-60% sequence homology. Each NOS polypeptide is comprised of oxygenase and reductase domains. An N-terminal oxygenase domain contains iron protoporphyrin IX (heme), BH4 and an arginine binding site, and a C-terminal reductase domain contains flavin mononucleotide (FMN), and a reduced nicotin-amide adenine dinucleotide phosphate (NADPH) binding site. 

FMN is the standard biochemical abbreviation for flavin mononucleotide (or riboflavin phosphate). The sodium salt (95-97% pure) of FMN is used. This grade 1s inexpensive and is available from Sigma Chemical Company. Its purpose is to effect recycling of the catalytic amount used of the much more costly NAD. A larger than stoichiometric amount of FMN is employed in order to ensure rapid recycling of the NAO. 

FMN Flavin mononucleotide as sodium salt Riboflavine 5 -(dihydrogen phosphate), monosodium salt (8,9) (130-40-5)... 

Flavin Mononucleotide, Sodium Salt Riboflavin 5 -Phosphate Ester Monosodium Salt Riboflavin 5 -Phosphate Ester Monosodium Salt, Dihydrate... 

Flavin mononucleotide (FMN)-adenosine and flavin adenine dinucleotide (FAD)-adenosine complexes show quenched triplet lifetimes compared to FMN alone, which is cited as evidence of intramolecular com-plexation between the flavins and adenosine by Shiga and Piette [142]. Adenosine phosphates also form complexes with FAD [143]. The com-plexation between a flavin and adenosine is identical to the intermolecular complexing of adenosine and flavin moieties, in the latter case enforced by hydrophobic bonding [144-146]. Rath and McCormick [147] have examined the riboflavin complexes of a series of purine ribose derivatives... 

The ribityl moiety is not linked to the isoalloxazine ring by a glycosidic linkage, and it is not strictly correct to caU FAD a dinucleotide. Nevertheless, this trivial name is accepted, as indeed is the even less correct term flavin mononucleotide for riboflavin phosphate. 

Enzymatic cofactors, such as nicotinamide adenine dinucleotide (NADH), nicotinamide adenine dinucleotide phosphate (NADPH), flavin adenine dinucleotide (EAD), flavin mononucleotide (EMN), and pyridoxal phosphate, are fluorescent and commonly found associated with various proteins where they are responsible for electron transport (see Fig. lb and Table 1). NADH and NADPH in the oxidized form are nonfluorescent, whereas conversely the flavins, FAD and EMN, are fluorescent only in the oxidized form. Both NADH and FAD fluorescence is quenched by the adenine found within their cofactor structures, whereas NADH-based cofactors generally remain fluorescent when interacting with protein structures. The fluorescence of these cofactors is often used to study the cofactors interaction with proteins as well as with related enzymatic kinetics (1, 9-12). However, their complex fluorescent characteristics have not led to widespread applications beyond their own intrinsic function. 

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