flavin-adenine-dinucleotide and Metabolism--Inborn-Errors

The aim of this short review chapter is to provide a brief summary of the relevance of riboflavin (Rf or vitamin B2) and its derived cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) for human neuromuscular bioenergetics.Therefore, as a completion of this book we would like to summarize what kind of human pathologies could derive from genetic disturbances of Rf transport, flavin cofactor synthesis and delivery to nascent apoflavoproteins, as well as by alteration of vitamin recycling during protein turnover.

Topics: Energy Metabolism; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Genetic Predisposition to Disease; Humans; Metabolism, Inborn Errors; Muscle, Skeletal; Neurons; Riboflavin

As an essential vitamin, the role of riboflavin in human diet and health is increasingly being highlighted. Insufficient dietary intake of riboflavin is often reported in nutritional surveys and population studies, even in non-developing countries with abundant sources of riboflavin-rich dietary products. A latent subclinical riboflavin deficiency can result in a significant clinical phenotype when combined with inborn genetic disturbances or environmental and physiological factors like infections, exercise, diet, aging and pregnancy. Riboflavin, and more importantly its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), play a crucial role in essential cellular processes including mitochondrial energy metabolism, stress responses, vitamin and cofactor biogenesis, where they function as cofactors to ensure the catalytic activity and folding/stability of flavoenzymes. Numerous inborn errors of flavin metabolism and flavoenzyme function have been described, and supplementation with riboflavin has in many cases been shown to be lifesaving or to mitigate symptoms. This review discusses the environmental, physiological and genetic factors that affect cellular riboflavin status. We describe the crucial role of riboflavin for general human health, and the clear benefits of riboflavin treatment in patients with inborn errors of metabolism.

Topics: Acyl-CoA Dehydrogenases; Aging; Animals; Diet; Electron Transport; Energy Metabolism; Fatty Acids; Female; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Folic Acid; Genetic Variation; Homocysteine; Humans; Immune System; Metabolism, Inborn Errors; Mitochondria; Mutation; Phenotype; Pregnancy; Protein Folding; Riboflavin; Riboflavin Deficiency

Topics: Adolescent; Alcohol Oxidoreductases; Brain; Diagnosis, Differential; Flavin-Adenine Dinucleotide; Humans; Magnetic Resonance Imaging; Male; Metabolism, Inborn Errors; Mutation

Dimethylglycine dehydrogenase (DMGDH) is a mitochondrial matrix flavoprotein that catalyses the demethylation of dimethylglycine to form sarcosine, accompanied by the reduction of the covalently bound FAD cofactor. Electron-transfer flavoprotein reoxidizes the reduced flavin and transfers reducing equivalents to the main mitochondrial respiratory chain through the enzyme ETF-ubiquinone oxidoreductase. DMGDH plays a prominent role in choline and 1-carbon metabolism. We have expressed the mature form of human DMGDH and the H109R variant identified in a DMGDH-deficient patient as N-terminally His(6)-tagged proteins in E. coli. The enzymes were purified to homogeneity by nickel affinity and anion exchange chromatography. The presence of FAD in the wild-type enzyme was confirmed by spectrophotometric analysis. The H109R variant, however, had only 47% of the wild-type level of bound flavin as expressed in E. coli, indicating its reduced affinity for FAD As previously described for rat enzyme studies, the wild-type human enzyme exhibited two K (m) values for N,N-dimethylglycine (K (m1) = 0.039 +/- 0.010 mmol/L and K(m2) = 15.4 +/- 1.2 mmol/L). The addition of 4 micromol/L tetrahydrofolate resulted in a slight decrease in specific activity and a substantial decrease in K (m2) (1.10 +/- 0.55 mmol/L). The flavinated H109R variant protein exhibited a 27-fold decrease in specific activity and a 65-fold increase in K (m), explaining its pathogenicity. Additionally, the current expression system represents a significant improvement over a previously described rat DMGDH expression system and will enhance our ability to further study this important metabolic enzyme.

Topics: Chromatography, Ion Exchange; Dimethylglycine Dehydrogenase; Dose-Response Relationship, Drug; Electrons; Flavin-Adenine Dinucleotide; Flavoproteins; Humans; Kinetics; Metabolism, Inborn Errors; Models, Chemical; Mutation; Oxygen; Recombinant Proteins; Sarcosine Dehydrogenase; Spectrophotometry

Glutathione reductase (GR) is a ubiquitous enzyme required for the conversion of oxidized glutathione (GSSG) to reduced glutathione (GSH) concomitantly oxidizing reduced nicotinamide adenine dinucleotide phosphate (NADPH) in a reaction essential for the stability and integrity of red cells. Mutations in the GR gene and nutritional deficiency of riboflavin, a co-factor required for the normal functioning of GR, can cause GR deficiency. We conducted a study on 1691 Saudi individuals to determine the overall frequency of GR deficiency and to identify whether the deficiency results from genetic or acquired causes or both. The activity of GR was measured in freshly prepared red cell haemolysate in the presence and absence of flavin adenine dinucleotide (FAD) and the activity coefficient (AC) was determined. Samples with low GR activity (> 2.0 IU/g haemoglobin) both in the presence and absence of FAD and an AC between 0.9 and 1.2 were considered GR-deficient. Samples with AC > or = 1.3 were considered riboflavin-deficient. The overall frequency of partial GR deficiency was 24.5% and 20.3% in males and females respectively. In addition, 17.8% of males and 22.4% of females suffered from GR deficiency due to riboflavin deficiency. This could be easily corrected by dietary supplementation with riboflavin. No cases of severe GR deficiency were identified.

Topics: Female; Flavin-Adenine Dinucleotide; Gene Frequency; Genetic Variation; Glutathione Reductase; Hemoglobins; Humans; Incidence; Male; Metabolism, Inborn Errors; Mutation; Nutrition Surveys; Population Surveillance; Prevalence; Riboflavin Deficiency; Saudi Arabia; Sex Distribution

The inherited metabolic disorder trimethylaminuria (fish-odor syndrome) is associated with defective hepatic N-oxidation of dietary-derived trimethylamine catalyzed by flavin-containing monooxygenase (FMO). As FMO3 encodes the major form of FMO expressed in adult human liver, it represents the best candidate gene for the disorder. The structural organization of FMO3 was determined by sequencing the products of exon-to-exon and vectorette PCR, the latter through the use of vectorette libraries constructed directly from genomic DNA. The gene contains one noncoding and eight coding exons. Knowledge of the exon/intron organization of the human FMO3 gene enabled each of the coding exons of the gene, together with their associated flanking intron sequences, to be amplified from genomic DNA and will thus facilitate the identification of mutations in FMO3 in families affected with fish-odor syndrome.

Topics: Exons; Flavin-Adenine Dinucleotide; Humans; Introns; Metabolism, Inborn Errors; Methylamines; Molecular Sequence Data; NADP; Odorants; Oxygenases; Polymerase Chain Reaction; Sequence Analysis, DNA

Multiple acyl-CoA dehydrogenation disorders result from generalized defects in intramitochondrial acyl-CoA dehydrogenation. Fibroblasts from a riboflavin-responsive multiple acyl-CoA dehydrogenation disorder patient catabolized 14C-butyrate, -octanoate, and -leucine normally after culture in riboflavin-supplemented medium (2 mg/L). After culture in riboflavin-depleted medium (< or = 1.4 micrograms/L), his cells oxidized the same substrates poorly at 20 to 33% of control (p < 0.05). Patient cells incubated in a wide range of D-[2-14C]riboflavin concentrations (3, 31.4, and 100 micrograms/L) synthesized 14C-flavin mononucleotide and 14C-flavin adenine dinucleotide (FAD) normally and had normal cytosolic 14C-flavin mononucleotide and 14C-FAD contents, which argues against defects in cellular riboflavin uptake and conversion to flavin mononucleotide and FAD. After culture in 31.4 micrograms 14C-riboflavin/L for 2 wk, 14C-FAD specific radioactivities plateaued and were similar in patient and control cells. However, culturing these uniformly labeled cells in riboflavin-depleted medium for 2 wk lowered the patient's cellular 14C-FAD content to only 23% of control levels. Similarly, after incubation in low 14C-riboflavin concentrations (4.4 micrograms/L), the patient's mitochondrial 14C-FAD content was only 51% of control after 1 h and 29% of control at 4 h. After a 4-h incubation in a high physiologic concentration of 14C-riboflavin (31.4 micrograms/L), which raised the patient's cellular 14C-FAD levels 3- to 4-fold, his mitochondrial 14C-FAD content rose to normal; control values did not change. We also investigated possible defective FAD binding to flavoenzymes essential for acyl-CoA dehydrogenation.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acyl Coenzyme A; Acyl-CoA Dehydrogenase; Cells, Cultured; Child, Preschool; Electron-Transferring Flavoproteins; Fatty Acid Desaturases; Fibroblasts; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Flavoproteins; Humans; Male; Metabolism, Inborn Errors; Mitochondria; Oxidation-Reduction; Riboflavin

Topics: Acyl Coenzyme A; Butyrates; Butyric Acid; Cells, Cultured; Fibroblasts; Flavin Mononucleotide; Flavin-Adenine Dinucleotide; Humans; Male; Metabolism, Inborn Errors; Mitochondria; Oxidation-Reduction; Phenotype; Riboflavin

Topics: Adult; Enzyme Induction; Erythrocytes; Flavin-Adenine Dinucleotide; Glutathione Reductase; Hematologic Diseases; Humans; Metabolism, Inborn Errors; Middle Aged; Riboflavin

Topics: Catalase; Cholinesterases; Clinical Enzyme Tests; Erythrocytes; Flavin-Adenine Dinucleotide; Galactosemias; Glucosephosphate Dehydrogenase Deficiency; Glutathione Reductase; Humans; L-Lactate Dehydrogenase; Lesch-Nyhan Syndrome; Metabolism, Inborn Errors; NAD; NADP; Nicotinic Acids; Pyridoxine; Riboflavin

Topics: Adult; Anemia; Electrophoresis; Erythrocytes; Flavin-Adenine Dinucleotide; Glutathione Reductase; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Male; Metabolism, Inborn Errors; NAD; Pedigree; Riboflavin

Topics: Acetylcholinesterase; Adenosine Triphosphate; Enzyme Activation; Enzyme Repression; Erythrocytes; Flavin-Adenine Dinucleotide; Glucosephosphate Dehydrogenase Deficiency; Glutathione; Glutathione Reductase; Hemolysis; Humans; Metabolism, Inborn Errors; Pyruvate Kinase

Topics: Adaptation, Biological; Adenosine Triphosphate; Black People; Coenzymes; Environment; Erythrocytes; Flavin-Adenine Dinucleotide; Glycerophosphates; Humans; Metabolism, Inborn Errors; Phosphates; Rickets; Tropical Climate; Vitamin D; White People

Glutathione reductase of hemolyzates from clinically normal subjects is activated by the addition of flavin-adenine dinucleotide. One-half maximum stimulation could be achieved by approximately 0.02 micromolar flavin-adenine dinucleotide; prior addition of adenosine triphosphate, adenosine diphosphate, or adenosine mnonophosphate prevented activation. Stimulation of glutathione reductase activity of red cells of normal subjects occurred when they were given 5 milligrams of riboflavin daily for 8 days. The degree of stimulation in vitro by flavin-adenine dinucleotide and in vivo by riboflavin was inversely proportional to dietary intake of riboflavin. The variety of clinical disorders which have been associated with glutathione reductase deficiency may have, as a common denominator, abnormalities in flavin-adenine dinucleotide formation.

Topics: Adenine Nucleotides; Catalysis; Erythrocytes; Flavin-Adenine Dinucleotide; Glutathione Reductase; Humans; Metabolism, Inborn Errors; Protein Binding; Riboflavin; Spectrophotometry