Myositis and cancer
Aug. 29, 2023
Nearly 3,000 illustrations, including video clips of neurologic disorders.
Every article is reviewed by our esteemed Editorial Board for accuracy and currency.
Full spectrum of neurology in 1,200 comprehensive articles.
Listen to MedLink on the go with Audio versions of each article.
The one-carbon units carried by reduced folate are involved in cytosolic, mitochondrial, and nuclear folate pools and used for the biosynthesis of purines, thymidylate, amino acids, and S-adenosylmethionine (SAM). Over-expressed gamma-glutamylhydrolase (γGH) facilitates intracellular folate exportation by converting polyglutamylfolates (folate-Glun) to monoglutamylfolates (folate-Glu1), leading to intracellular folate deficiency (thickened circle and arrows in shadowed box).
Legend: AICAR: aminoimidazolecarboxamide ribonucleotide; AICART, aminoimidazolecarboxamide ribonucleotide transformylase; ADP: adenosine diphosphate; ATP: adenosine triphosphate; B2: riboflavin; B6: pyridoxal phosphate, the activated form of vitamin B6; B12: cobalamin (vitamin B12); 5,10-CH2-THF: 5,10-methylenetetrahydrofolate; DHF: dihydrofolate ; DHFR, dihydrofolate reductase; 5-CHO-THF: 5-formyltetrahydrofolate; 10-CHO-THF: 10-formyltetrahydrofolate; CO2: carbon dioxide; dTMP: deoxythymidine monophosphate; dUMP: deoxyuridine monophosphate; FDH, 10-formyltetrahydrofolate dehydrogenase; γGH: γ-glutamylhydrolase; GAR: glycinamide ribonucleotide; GART, glycinamide ribonucleotide transformylase; Glu: glutamate: H+: proton; Hcy: homocysteine; H2O: water; MAT, methionine adenosyl transferase; Met: methionine; MT, methyltransferase; MTHF: methylenetetrahydrofolate ; MTHFD, methylenetetrahydrofolate dehydrogenase; MTHFR, methylenetetrahydrofolate reductase; MTHFS, 5,10-methenyltetrahydrofolate synthetase; MTR, 5-methyltetrahydrofolate-homocysteine methyltransferase; NADP+: nicotinamide adenine dinucleotide phosphate; NADPH: nicotinamide adenine dinucleotide phosphate (the reduced form of NADP⁺); Pi: inorganic phosphate; SAHH, S- adenosylhomocysteine hydrolase; SAH: S-adenosylhomocystein; SAM: S-adenosylmethionine; SHMT, serine hydroxymethyltransferase; THF: tetrahydrofolate; TS, thymidylate synthase. (Source: Tu HC, Lee GH, Hsiao TH, et al. One crisis, diverse impacts: tissue-specificity of folate deficiency-induced circulation defects in zebrafish larvae. PLoS One 2017;12(11):e0188585.) (Creative Commons Attribution License.)