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Riboflavin, also known as vitamin B2, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide. These coenzymes are involved in energy metabolism, cellular respiration, and antibody production, as well as normal growth and development. The coenzymes are also required for the metabolism of niacin, vitamin B6, and folate. Riboflavin is prescribed to treat corneal thinning, and taken orally, may reduce the incidence of migraine headaches in adults.
Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage. Folate is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division. As humans cannot make folate, it is required in the diet, making it an essential nutrient. It occurs naturally in many foods. The recommended adult daily intake of folate in the U.S. is 400 micrograms from foods or dietary supplements.
In biochemistry, flavin adenine dinucleotide (FAD) is a redox-active coenzyme associated with various proteins, which is involved with several enzymatic reactions in metabolism. A flavoprotein is a protein that contains a flavin group, which may be in the form of FAD or flavin mononucleotide (FMN). Many flavoproteins are known: components of the succinate dehydrogenase complex, α-ketoglutarate dehydrogenase, and a component of the pyruvate dehydrogenase complex.
Exercise intolerance is a condition of inability or decreased ability to perform physical exercise at the normally expected level or duration for people of that age, size, sex, and muscle mass. It also includes experiences of unusually severe post-exercise pain, fatigue, nausea, vomiting or other negative effects. Exercise intolerance is not a disease or syndrome in and of itself, but can result from various disorders.
Systemic primary carnitine deficiency (SPCD) is an inborn error of fatty acid transport caused by a defect in the transporter responsible for moving carnitine across the plasma membrane. Carnitine is an important amino acid for fatty acid metabolism. When carnitine cannot be transported into tissues, fatty acid oxidation is impaired, leading to a variety of symptoms such as chronic muscle weakness, cardiomyopathy, hypoglycemia and liver dysfunction. The specific transporter involved with SPCD is OCTN2, coded for by the SLC22A5 gene located on chromosome 5. SPCD is inherited in an autosomal recessive manner, with mutated alleles coming from both parents.
Very long-chain acyl-coenzyme A dehydrogenase deficiency is a fatty-acid metabolism disorder which prevents the body from converting certain fats to energy, particularly during periods without food.
Methionine synthase also known as MS, MeSe, MTR is responsible for the regeneration of methionine from homocysteine. In humans it is encoded by the MTR gene (5-methyltetrahydrofolate-homocysteine methyltransferase). Methionine synthase forms part of the S-adenosylmethionine (SAMe) biosynthesis and regeneration cycle, and is the enzyme responsible for linking the cycle to one-carbon metabolism via the folate cycle. There are two primary forms of this enzyme, the Vitamin B12 (cobalamin)-dependent (MetH) and independent (MetE) forms, although minimal core methionine synthases that do not fit cleanly into either category have also been described in some anaerobic bacteria. The two dominant forms of the enzymes appear to be evolutionary independent and rely on considerably different chemical mechanisms. Mammals and other higher eukaryotes express only the cobalamin-dependent form. In contrast, the distribution of the two forms in Archaeplastida (plants and algae) is more complex. Plants exclusively possess the cobalamin-independent form, while algae have either one of the two, depending on species. Many different microorganisms express both the cobalamin-dependent and cobalamin-independent forms.
Glutaric acidemia type 2 is an autosomal recessive metabolic disorder that is characterised by defects in the ability of the body to use proteins and fats for energy. Incompletely processed proteins and fats can build up, leading to a dangerous chemical imbalance called acidosis.
Folate deficiency, also known as vitamin B9 deficiency, is a low level of folate and derivatives in the body. Signs of folate deficiency are often subtle. A low number of red blood cells (anemia) is a late finding in folate deficiency and folate deficiency anemia is the term given for this medical condition. It is characterized by the appearance of large-sized, abnormal red blood cells (megaloblasts), which form when there are inadequate stores of folic acid within the body.
Acyl-CoA dehydrogenases (ACADs) are a class of enzymes that function to catalyze the initial step in each cycle of fatty acid β-oxidation in the mitochondria of cells. Their action results in the introduction of a trans double-bond between C2 (α) and C3 (β) of the acyl-CoA thioester substrate. Flavin adenine dinucleotide (FAD) is a required co-factor in addition to the presence of an active site glutamate in order for the enzyme to function.
Dihydrolipoamide dehydrogenase (DLD), also known as dihydrolipoyl dehydrogenase, mitochondrial, is an enzyme that in humans is encoded by the DLD gene. DLD is a flavoprotein enzyme that oxidizes dihydrolipoamide to lipoamide.
Levomefolic acid (INN, also known as L-5-MTHF, L-methylfolate and L-5-methyltetrahydrofolate and (6S)-5-methyltetrahydrofolate, and (6S)-5-MTHF) is the primary biologically active form of folate used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine. It is also the form found in circulation and transported across membranes into tissues and across the blood–brain barrier. In the cell, L-methylfolate is used in the methylation of homocysteine to form methionine and tetrahydrofolate (THF). THF is the immediate acceptor of one carbon unit for the synthesis of thymidine-DNA, purines (RNA and DNA) and methionine. The un-methylated form, folic acid (vitamin B9), is a synthetic form of folate, and must undergo enzymatic reduction by dihydrofolate reductase (DHFR) to become biologically active.
Electron-transferring-flavoprotein dehydrogenase is an enzyme that transfers electrons from electron-transferring flavoprotein in the mitochondrial matrix, to the ubiquinone pool in the inner mitochondrial membrane. It is part of the electron transport chain. The enzyme is found in both prokaryotes and eukaryotes and contains a flavin and FE-S cluster. In humans, it is encoded by the ETFDH gene. Deficiency in ETF dehydrogenase causes the human genetic disease multiple acyl-CoA dehydrogenase deficiency.
Methionine synthase reductase, also known as MSR, is an enzyme that in humans is encoded by the MTRR gene.
Folate receptors bind folate and reduced folic acid derivatives and mediates delivery of tetrahydrofolate to the interior of cells. It is then converted from monoglutamate to polyglutamate forms - such as 5-methyltetrahydrofolate - as only monoglutamate forms can be transported across cell membranes. Polyglutamate forms are biologically active enzymatic cofactors required for many folate-dependent processes such as folate-dependent one-carbon metabolism. These proteins are attached to the membrane by a GPI anchor. A riboflavin-binding protein required for the transport of riboflavin to the developing oocyte in chicken also belong to this family.
Hereditary folate malabsorption (HFM) is a rare autosomal recessive disorder caused by loss-of-function mutations in the proton-coupled folate transporter (PCFT) gene, resulting in systemic folate deficiency and impaired delivery of folate to the brain.
NAD-dependent methylenetetrahydrofolate dehydrogenase 2-like protein (MTHFD2L), also known as bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase 2, is an enzyme that in humans is encoded by the MTHFD2L gene on chromosome 4. This enzyme localizes to the inner mitochondrial membrane, where it performs the NADP+-dependent dehydrogenase/cyclohydrolase activity as part of the mitochondrial pathway to convert folate to formate. It is associated with fluctuations in cytokine secretion in response to viral infections and vaccines.
Cerebral folate deficiency is a condition in which concentrations of 5-methyltetrahydrofolate are low in the brain as measured in the cerebral spinal fluid despite being normal in the blood. Symptoms typically appear at about 5 to 24 months of age. Without treatment there may be poor muscle tone, trouble with coordination, trouble talking, and seizures.
The mitochondrial folate transporter (MTF) is a transport protein that facilitates the transfer of tetrahydrofolate across the inner mitochondrial membrane. It is encoded by the SLC25A32 gene and belongs to the mitochondrial carrier superfamily.
References
- ↑ Peng, Min-Zhi; Shao, Yong-Xian; Li, Xiu-Zhen; Zhang, Kang-Di; Cai, Yan-Na; Lin, Yun-Ting; Jiang, Min-Yan; Liu, Zong-Cai; Su, Xue-Ying; Zhang, Wen; Jiang, Xiao-Ling; Liu, Li (2022-06-21). "Mitochondrial FAD shortage in SLC25A32 deficiency affects folate-mediated one-carbon metabolism". Cellular and molecular life sciences: CMLS. 79 (7): 375. doi:10.1007/s00018-022-04404-0. ISSN 1420-9071. PMID 35727412.
- ↑ Al Shamsi B, Al Murshedi F, Al Habsi A, Al-Thihli K (November 2021). "Hypoketotic hypoglycemia without neuromuscular complications in patients with SLC25A32 deficiency". European Journal of Human Genetics. doi:10.1038/s41431-021-00995-7. PMID 34764427.
- ↑ Schiff M, Veauville-Merllié A, Su CH, Tzagoloff A, Rak M, Ogier de Baulny H, Boutron A, Smedts-Walters H, Romero NB, Rigal O, Rustin P, Vianey-Saban C, Acquaviva-Bourdain C (February 2016). "SLC25A32 Mutations and Riboflavin-Responsive Exercise Intolerance". The New England Journal of Medicine. 374 (8): 795–7. doi:10.1056/NEJMc1513610. PMC 4867164 . PMID 26933868.
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