Flavins monophosphate

Riboflavin (vitamin B2) has been reported to improve the exercise capacity of a patient with Complex I deficiency. After conversion to flavin monophosphate and FAD, riboflavin functions as a cofactor for electron transport in Complex I, Complex II, and electron transfer flavopro-tein. Nicotinamide has been used because Complex I accepts electrons from NADH and ultimately transfers electrons to Q10. 

The worst example is given by the flavin nucleotides FMN and FAD, the first of which is no nucleotide at all and the second no dinucleotide. The term FMN should simply be changed into FMP, viz. (ribo)flavin-monophosphate, while the abbreviation FAD might even be preserved as representing flavin-adenine-diphosphate . 

Flavin adenine dinucleotide Riboflavin 5 -monophosphate Riboflavin 5 -monophosphate, reduced form Fast protein liquid chromatography (Pharmacia)... 

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). 

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]. 

Riboflavin (vitamin B2 6.18) consists of an isoalloxazine ring linked to an alcohol derived from ribose. The ribose side chain of riboflavin can be modified by the formation of a phosphoester (forming flavin mononucleotide, FMN, 6.19). FMN can be joined to adenine monophosphate to form flavin adenine dinucleotide (FAD, 6.20). FMN and FAD act as co-enzymes by accepting or donating two hydrogen atoms and thus are involved in redox reactions. Flavoprotein enzymes are involved in many metabolic pathways. Riboflavin is a yellow-green fluorescent compound and, in addition to its role as a vitamin, it is responsible for the colour of milk serum (Chapter 11). 

FMN, riboflavin-5 -monophosphate (flavin mononucleotide) TARF, tetracetylriboflavin Rfl, riboflavin Lfl, lumiflavin... 

Flavin adenine diphosphate (FAD, flavin adenine dinucleotide) and riboflavin 5 -monophosphate (FMN, flavin mononucleotide), whose structures are shown in Fig. 15-7, are perhaps the most versatile of all... 

Fig. 2.1. Examples from The Energy Hall of Fame. These molecules not only deliver energy, but transfer special groups in the process. Acyl, RCO— ADP, adenosine diphosphate ATP, adenosine triphosphate dUMP deoxyuridine monophosphate FAD, flavin adenine dinucleotide GTP, guanosine triphosphate NADH, nicotinamide adenine dinucleotide NADP, nicotinamide adenine dinucleotide phosphate P, phosphate TMP, thymidine monophosphate UDP, uridine diphosphate UTP, uridine triphosphate.

Glutathione reductase (EC 1.8.1.7 formerly EC 1.6.4.2 GSR) links the glutathione pathway to the hexose monophosphate pathway through the reversible oxidation and reduction of NADP. Flavin adenine dinucleotide (FAD) is necessary as a cofactor. The enzyme maintains high levels of reduced glutathione in the cell. Two isoforms exist, a mitochondrial and cytoplasmic form, produced by alternative initiation. The molecule is a homodimer, linked by a disulfide bridge. Each subunit (522 amino acids 56kDa) is divided into four domains of which domains one and two bind FAD and NADPH, respectively and domain four forms the interface. ... 

FIGURE 5.3 The flavin coenzymes FAD and FMN. Whereas FMN consists simply of riboflavin monophosphate, FAD has an AMP unit joined to riboflavin monophosphate. Note that in contrast to NAD+, flavins can be half-reduced to the stable radical FADH or fully reduced to the dihydroflavin shown. 

Other Coenzymes and Cofactors.— The chemical synthesis of riboflavin phosphates and their acetyl derivatives has been reinvestigated. Riboflavin 4 -monophosphate (10) is an important contaminant of commercial flavin mononucleotide (FMN), and... 

Flavin mononucleotide (FMN) An isoalloxazine ring bound to ribosyl monophosphate in an A-glycosidic bond. FMN can accept two electrons or donate one at a time to another electron acceptor. 

FMN, flavin mononucleotide GMP, guanosine monophosphate GTP, guanosine triphosphate NAD, nicotinamide-adenine dinucleotide (NAD+, oxidized form NADH, reduced form). 

Abbreviations used NAD+ = nicotinamide adenine dinucleotide NADH e reduced nicotinamide adenine dinucleotide NADP = nicotinamide adenine dinudeotide phosphate NAD PH reduced nicotinamide adenine dinucleotide phosphate NMN, NMN+ nicotinamide mononucleotide NMNH2 = reduced nicotinamide mononucleotide a-NAD a-nicotinamide adenine dinucleotide AMP = 5 -adenylic acid 3,5 -AMP adenosine 3, 5 -cycIic phosphate 3 ,5 -UMP = uridine 3, 5 -cyclic phosphate 3, 5 -CMP cytidine 3, 5-cyclic phosphate 3 f5 GMP = guanosine 3 5f-cyclic phosphate 3, 5 TMP thymidine 3, 5 -cyclic phosphate Dibutyryl-3, 5 -AMP = N6,02-dibutyryladenosine 3, 5 -cyclic phosphate 2, 3 -UMP = uridine 2 ,3 -cyclic monophosphate 2, 3 -CMP cytidine 2, 3 -cyclic monophosphate 2, 3 -AMP = adenosine 2, 3 -cyclic monophosphate 2 ,3 -GMP = guanosine 2 3 -cyclic monophosphate 2 -UMP = uridine 2 -phosphate -UMP uridine -phosphate 5 -UMP = uridine 5 phosphate Poly U polyuridylic acid ADP = adenosine 5 -diphosphate FAD = flavin adenine dinucleotide UpA, UpU, ApU and ApA x dinucleoside phosphates of uridine and/or adenine. c See original references for experimental conditions and additional data. 

Another enzyme cofactor, flavine adenine dinucleotide (FAD) disodium salt, has been studied by 13C nmr. Assignments of the resonances have been made by comparing the spectrum of FAD with its constituents, adenosine 5 -diphosphate trisodium salt and riboflavin -monophosphate sodium salt (Breitmaier and Voelter, 1972). 

Riboflavin 5 -phosphate CAS 146-17-8 EINECS/ELINCS 205-664-7 Synonyms Flavin mononucleotide FMN Riboflavin 5 -(dihydrogen phosphate) Riboflavin monophosphate Vitamin B2 phosphate... 

Vitamin B2 is riboflavin (ll.lOSe), which is utilised for the synthesis of coenzymes flavin mononucleotide (riboflavin monophosphate) (FMN), and flavin adenine dinucleotide (FAD) (11.110) and (11.28). Riboflavin was isolated from yeast in 1932 [33]. 

GMP reductase (EC 1.6.6.8) a flavin enzyme which catalyses the conversion of guanosine S -monophosphate to inosinic acid in a sin e step. It is part of the system for converting guanine to adenine compounds. 

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