Riboflavin metabolism

Metabolism of Cofactors, Vitamins, and Other Substances Thiamin metabolism Riboflavin metabolism Vitamin B6 metabolism Nicotinate and nicotinamide metabolism... 

Figure 7.2. Products of riboflavin metabolism. Relative molecular masses (Mr) riboflavin, 376.4 lumiflavin, 256.3 8- and 7-carboxylumichrome, 296.2 and lumichrome, 242.2.

Cimino JA, Jhangiani S, Schwartz E, and Cooperman JM (1987) Riboflavin metabolism in the hypothyroid human adult. Proceedings of the Society for Experimental Biology and Medicine 184,151-3. 

Pinto J, Huang YP, and Riviin RS (1981) Inhibition of riboflavin metabolism in rat tissues by chlorpromazine, imipramine, and amitriptyline. Journal of Clinical Investigation 67,1500-6. 

FIGURE 9.73 Riboflavin metabolism and FAD covalently bound to an enz3m e via a residue of histidine. 

Takenouchi K (1963) Thiamine and Riboflavine Metabolism in Skin Disease. Toda Printing Company, Chiba City, Japan... 

Riboflavin, commonly known as vitamin B2, is metabolized inside cells to flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), two very important enzyme cofactors. These molecules possess rather unique and versatile chemical properties, which confer on them the ability to be among the most important redox cofactors found in a broad range of enzymes. In this chapter we provide a brief description of riboflavin metabolism and chemistry, overview the different flavoenzymes engaged in fatty acid p-oxidation and their respective roles. We also highlight recent studies shedding light on the cellular processes and biological effects of riboflavin supplementation in the context of metabolic disease. 

Figure 37.1 Riboflavin metabolism and cellular processing pathways. (A) Riboflavin and flavin intake is made via the diet, either in riboflavin-rich aliments or flavoproteins. In the latter, digestion in the stomach releases FAD and FMN cofactors. Riboflavin and flavins achieve a high concentration in the liver, spleen and cardiac muscle a concentration of about 30 nM riboflavin is also reached in the plasma circulation. (B) Riboflavin is imported into the cell and into the mitochondria via specific transporters (white circles in membranes). In the cytoplasm, flavin kinase (FK) and FAD synthetase (FADS) consecutively convert riboflavin into FMN and FAD, at the expense of ATP. An identical mechanism is also thought to be present inside the mitochondria, although a mitochondrial FK remains to be identified. FAD can also be imported into the mitochondria, or diffuse passively when the riboflavin concentrations are high. Figures reprinted from Henriques et al. (2010), with permission.

In this section we provide a short overview of the mitochondrial p-oxidation process and focus more specifically on the several flavoenzymes that participate in the pathway, as their adequate function and folding strongly relies on riboflavin metabolism to assure flavin biosynthesis. 

Fujlwara, M., 1954, Influence of thiamine on riboflavin metabolism. Vitamin, 7 206-208. 

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