Flavin adenine mononucleotide

So what does riboflavin do As such riboflavin does nothing. Like thiamine, riboflavin must undergo metabolic change to become effective as a coenzyme. It fact, it undergoes two reactions. The first converts riboflavin to riboflavin-5-phosphate (commonly known as flavin adenine mononucleotide, FMN), about which we will say no more, and the second converts it to flavin adenine dinucleotide, FAD. The flavins are a class of redox agents of very general importance in biochemistry. FAD is the oxidized form and FADH2 is the reduced form. ... 

Ribofiavin also known as vitamin B2 the precursor to the coenzymes flavin adenine mononucleotide, FMN, and flavin adenine dinucleotide, FAD. 

The oxidations are performed in aqueous buffer solution at pH 9.0 with less than stoichiometric amounts of nicotineamide adenine dinucleotide (NAD+) as coenzyme, which is expensive and therefore must be recycled. This can be done in such oxidations in several ways. The simplest is to simultaneously oxidize the reduced nicotineamide adenine dinucleotide formed with a stoichiometric amount (based on the diol) of inexpensive flavin adenine mononucleotide (FMN)167. In this manner gram quantities of the corresponding lactone may be readily obtained scaling up the reaction, however, seems to be a problem167. 

A more efficient system which allows the use of catalytic amounts of nicotineamide adenine dinucleotide and flavin adenine mononucleotide and allows the reaction to be efficiently scaled up, utilizes a catalytic recycling system. Flavin adenine mononucleotide (FMN) reductase (E.C. 1.6.8.1) is used to catalyze the oxidation of reduced nicotineamide adenine dinucleotide by FMN under formation of reduced flavin adenine mononucleotide which in turn is oxidized in both versions to flavin adenine mononucleotide by oxygen169. 

These yellow redox systems all contain the conjugated tricyclic isoalloxazine ring system. Riboflavin, vitamin B2, is an isoalloxazine which is phosphorylated and then adenylated to two active redox coenzyme forms - FMN (flavin adenine mononucleotide, R = phosphorylated ribose) and FAD (flavin adenine dinucleotide, adenylated FMN). 

Both flavin adenine dinucleotide (FAD) and flavin adenine mononucleotide (FMN)-containing DIs are found, some specific for NAD, whereas others for NADP. They have been used for staining dehydrogenase-rich tissues and in attempted appKcations for the regeneration of the cofactor such as in bioelectroanalytical devices and flow systems (see following text) and in bioorganic synthetic reactions. 

Methods for the determination of riboflavin in food samples should account for its different forms, namely flavin mononucleotide and flavin adenine mononucleotide. 

Fig. 5.12. Nitrate reductase and its electron donors. Key FAD, Flavin adenine dinucleotide FMN, Flavin adenine mononucleotide Mo, Molybdenum.

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,... 

Riboflavin is heat-stable in the absence of light, but extremely photosensitive. It has a high degree of natural fluorescence when excited by UV light. This property can be used for detection and determination. Two coenzymes (Fig. 2), flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), are derived from riboflavin. 

All the complexes consist of several subunits (Table 2) complex I has a flavin mononucleotide (FMN) prosthetic group and complex II a flavin adenine dinucleotide (FAD) prosthetic group. Complexes I, II, and III contain iron-sulphur (FeS) centers. These centers contain either two, three, or four Fe atoms linked to the sulphydryl groups of peptide cysteine residues and they also contain acid-labile sulphur atoms. Each center can accept or donate reversibly a single electron. 

Flavoprotein enzymes contain flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) as prosthetic groups. FMN and FAD are formed in the body from the vitamin riboflavin (Chapter 45). FMN and FAD are usually tighdy—but not covalendy—bound to their respecdve apoenzyme proteins. Metalloflavopro-teins contain one or more metals as essential cofactors. 

Riboflavin fulfills its role in metabolism as the coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) (Figure 45-10). FMN is formed by ATP-dependent phosphorylation of riboflavin, whereas FAD is synthesized by further reaction of FMN with ATP in which its AMP moiety is transferred to the... 

FIGURE 10.1 The structural formula of riboflavin and partial structures of riboflavin compounds. The latter show only those portions of the molecule that differ from riboflavin. 1 — Riboflavin (RF), 2 — flavin mononucleotide or 5 -riboflavin monophosphate (FMN or 5 -FMN), 3 — flavin adenine dinucleotide (FAD). 

FIGURE 32-7 Sources of free radical formation which may contribute to injury during ischemia-reperfusion. Nitric oxide synthase, the mitochondrial electron-transport chain and metabolism of arachidonic acid are among the likely contributors. CaM, calcium/calmodulin FAD, flavin adenine dinucleotide FMN, flavin mononucleotide HtT, tetrahydrobiopterin HETES, hydroxyeicosatetraenoic acids L, lipid alkoxyl radical LOO, lipid peroxyl radical NO, nitric oxide 0 "2, superoxide radical. 

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... 

C. Andres-Lacueva, F. Mattivi and D. Tonon, Determination of riboflavin, flavin mononucleotide and flavin-adenin dinucleotide in wine and other beverages by high-performance liquid chromatography with fluorescence detection. J. Chromatogr.A 823 (1998) 355-363. 

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