MTHFD1 is a gene located in humans on chromosome 14 that encodes for a protein with three distinct enzymatic activities. C-1-tetrahydrofolate synthase, cytoplasmic also known as C1-THF synthase is an enzyme that in humans is encoded by the MTHFD1 (methylenetetrahydrofolate dehydrogenase 1) gene. [4] [5] [6]
This gene encodes a protein that possesses three distinct enzymatic activities, methylenetetrahydrofolate dehydrogenase (1.5.1.5), methenyltetrahydrofolate cyclohydrolase (3.5.4.9) and formate–tetrahydrofolate ligase (6.3.4.3). Each of these activities catalyzes one of three sequential reactions in the interconversion of 1-carbon derivatives of tetrahydrofolate, which are substrates for methionine, thymidylate, and de novo purine syntheses. The trifunctional enzymatic activities are conferred by two major domains, an aminoterminal portion containing the dehydrogenase and cyclohydrolase activities and a larger synthetase domain. [6] [7]
Mutations of the MTHFD1 gene may cause methylenetetrahydrofolate dehydrogenase 1 deficiency, also known as combined immunodeficiency and megaloblastic anemia with or without hyperhomocysteinemia (CIMAH). [7]
Methylenetetrahydrofolatereductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the MTHFR gene. Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. Natural variation in this gene is common in otherwise healthy people. Although some variants have been reported to influence susceptibility to occlusive vascular disease, neural tube defects, Alzheimer's disease and other forms of dementia, colon cancer, and acute leukemia, findings from small early studies have not been reproduced. Some mutations in this gene are associated with methylenetetrahydrofolate reductase deficiency. Complex I deficiency with recessive spastic paraparesis has also been linked to MTHFR variants. In addition, the aberrant promoter hypermethylation of this gene is associated with male infertility and recurrent spontaneous abortion.
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.
Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a folic acid derivative.
Purine metabolism refers to the metabolic pathways to synthesize and break down purines that are present in many organisms.
5,10-Methylenetetrahydrofolate (N5,N10-Methylenetetrahydrofolate; 5,10-CH2-THF) is cofactor in several biochemical reactions. It exists in nature as the diastereoisomer [6R]-5,10-methylene-THF.
Bifunctional purine biosynthesis protein PURH is a protein that in humans is encoded by the ATIC gene.
10-Formyltetrahydrofolate (10-CHO-THF) is a form of tetrahydrofolate that acts as a donor of formyl groups in anabolism. In these reactions 10-CHO-THF is used as a substrate in formyltransferase reactions.
In enzymology, a thymidylate synthase (FAD) (EC 2.1.1.148) is an enzyme that catalyzes the chemical reaction
In enzymology, a formate—tetrahydrofolate ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a methenyltetrahydrofolate cyclohydrolase (EC 3.5.4.9) is an enzyme that catalyzes the chemical reaction
Methionine synthase reductase, also known as MSR, is an enzyme that in humans is encoded by the MTRR gene.
Bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase, mitochondrial is an enzyme that in humans is encoded by the MTHFD2 gene.
10-formyltetrahydrofolate dehydrogenase is an enzyme that in humans is encoded by the ALDH1L1 gene.
5,10-Methenyltetrahydrofolate (5,10-CH=THF) is a form of tetrahydrofolate that is an intermediate in metabolism. 5,10-CH=THF is a coenzyme that accepts and donates methenyl (CH=) groups.
Phosphoribosylglycinamide formyltransferase (EC 2.1.2.2, 2-amino-N-ribosylacetamide 5'-phosphate transformylase, GAR formyltransferase, GAR transformylase, glycinamide ribonucleotide transformylase, GAR TFase, 5,10-methenyltetrahydrofolate:2-amino-N-ribosylacetamide ribonucleotide transformylase) is an enzyme with systematic name 10-formyltetrahydrofolate:5'-phosphoribosylglycinamide N-formyltransferase. This enzyme catalyses the following chemical reaction
Monofunctional C1-tetrahydrofolate synthase, mitochondrial also known as formyltetrahydrofolate synthetase, is an enzyme that in humans is encoded by the MTHFD1L gene.
In molecular biology, enzymes containing the cyclodeaminase domain function in channeling one-carbon units to the folate pool. In most cases, this domain acts as a formimidoyltetrahydrofolate cyclodeaminase, which catalyses the cyclisation of formimidoyltetrahydrofolate to methenyltetrahydrofolate as shown in reaction (1). In the methylotrophic bacterium Methylobacterium extorquens, however, it acts as a methenyltetrahydrofolate cyclohydrolase, which catalyses the interconversion of formyltetrahydrofolate and methylenetetrahydrofolate, as shown in reaction (2).
The purinosome is a putative multi-enzyme complex that carries out de novo purine biosynthesis within the cell. It is postulated to include all six of the human enzymes identified as direct participants in this ten-step biosynthetic pathway converting phosphoribosyl pyrophosphate to inosine monophosphate:
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.
Riboflavin-responsive exercise intolerance is a rare disorder caused by mutations of the SLC25A32 gene that encodes the mitochondrial folate transporter. Patients suffer from exercise intolerance and may have disrupted motor function.
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