HomocysteineMetabolic pathwaysMethionine metabolismEnzymeGlutathioneDeficientSerineFolateTaurineHomocystinuriaGeneDietaryActivityStepResultsEffectsHighMTHFRRemethylation pathwayBiochemicalCofactorVitamin D deficienRegulatesMetabolicAutosomalHomocysteine levelsPyridoxineAmino acidsBetaineDiagnosisLevelsCommon
Homocysteine15
- It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine: L-serine + L-homocysteine ⇌ {\displaystyle \rightleftharpoons } L-cystathionine + H2O CBS uses the cofactor pyridoxal-phosphate (PLP) and can be allosterically regulated by effectors such as the ubiquitous cofactor S-adenosyl-L-methionine (adoMet). (wikipedia.org)
- Other names in common use include: β-thionase, cysteine synthase, L-serine hydro-lyase (adding homocysteine), methylcysteine synthase, serine sulfhydrase, and serine sulfhydrylase. (wikipedia.org)
- Transsulfuration, catalyzed by CBS, converts homocysteine to cystathionine, which cystathione gamma lyase converts to cysteine. (wikipedia.org)
- CBS occupies a pivotal position in mammalian sulfur metabolism at the homocysteine junction where the decision to conserve methionine or to convert it to cysteine via the transsulfuration pathway, is made. (wikipedia.org)
- Nucleophilic attack by the thiolate of homocysteine on the aminoacrylate and reprotonation at Cα generate the external aldimine of cystathionine. (wikipedia.org)
- Simplified picture showing homocysteine involvement in different metabolic pathways, as well as the role of vitamins B-6, B-12, and folate as a co-factors in this pathway. (medscape.com)
- Homocysteine is metabolized by means of 2 pathways: remethylation and transsulfuration. (medscape.com)
- The remethylation pathway comprises 2 intersecting biochemical pathways and results in the transfer of a methyl group (CH 3 ) to homocysteine from methylcobalamin, which receives its methyl group from S-adenosylmethionine (SAM), from 5-methyltetrahydrofolate (an active form of folic acid), or from betaine (trimethylglycine). (medscape.com)
- Two other interrelated pathways of methionine metabolism can produce accumulation of homocysteine and its metabolites: defective methylcobalamin synthesis (homocystinuria II) and abnormality in MTHFR (homocystinuria III). (mhmedical.com)
- The transsulfuration pathway of methionine/homocysteine degradation produces the amino acids cysteine and taurine. (medscape.com)
- The amino acid serine, which is a downstream metabolite generated from betaine via the homocysteine remethylation pathway is another necessary step. (medscape.com)
- Urine methionine and homocysteine levels are elevated because of deficient levels of cystathionine beta-synthase. (medscape.com)
- Cystathionine β-synthase (CBS) is a key regulator of sulfur amino acid metabolism, taking homocysteine from the methionine cycle to the biosynthesis of cysteine via the trans-sulfuration pathway. (rhea-db.org)
- Levels of homocysteine (Hcy), beta-amyloid 1-42 (Aß1-42), S-adenosine methionine (SAM) and S-adenosine homocysteine (SAH) were detected by ELISA. (bvsalud.org)
- Under such metabolic stress conditions, supplies of L-cysteine for glutathione synthesis become limiting, so homocysteine is diverted from the transmethylation pathway (which forms methionine) into the transsulfuration pathway (which forms cystathionine). (pathbank.org)
Metabolic pathways2
- Methionine can then be used to produce SAM, the body's universal methyl donor, which participates in several other key metabolic pathways, including the methylation of DNA and myelin. (medscape.com)
- 1, 3-Diaminopropane is involved in the arginine/proline metabolic pathways and the beta-alanine metabolic pathway. (pathbank.org)
Methionine metabolism1
- Homocystinuria is an inherited autosomal recessive defect in methionine metabolism that is caused by a deficiency in cystathionine synthase. (medscape.com)
Enzyme4
- Cystathionine-β-synthase, also known as CBS, is an enzyme (EC 4.2.1.22) that in humans is encoded by the CBS gene. (wikipedia.org)
- The human enzyme cystathionine β-synthase is a tetramer and comprises 551 amino acids with a subunit molecular weight of 61 kDa. (wikipedia.org)
- However, the Anopheles gambiae sequence has a longer N-terminal extension than the human enzyme and contains the conserved histidine and cysteine heme ligand residues like the human heme. (wikipedia.org)
- It is caused by the deficiency of the enzyme cystathionine beta synthase, and the deficiency of folic acid, vitamin B 12 and pyridoxine (vitamin B 6 ), or mutations of related enzymes. (mhmedical.com)
Glutathione2
- alpha-Ketobutyrate is produced by amino acid catabolism (threonine and methionine) and glutathione anabolism (cysteine formation pathway) and is metabolized to propionyl-CoA and carbon dioxide (PMID: 20526369). (pathbank.org)
- 2-Hydroxybutyrate is released as a byproduct when cystathionine is cleaved into cysteine that is incorporated into glutathione. (pathbank.org)
Deficient1
- 2-Hydroxybutyric acid generally appears at high concentrations in situations related to deficient energy metabolism (e.g. birth asphyxia) and also in inherited metabolic diseases affecting the central nervous system during neonatal development, such as "cerebral" lactic acidosis, glutaric aciduria type II, dihydrolipoyl dehydrogenase (E3) deficiency, and propionic acidemia. (pathbank.org)
Serine1
- 2-Ketobutyric acid is a substance that is involved in the metabolism of many amino acids (glycine, methionine, valine, leucine, serine, threonine, isoleucine) as well as propanoate metabolism and C-5 branched dibasic acid metabolism. (pathbank.org)
Folate1
- Findings from experimental studies have indicated that thyroid hormones affect folate metabolism. (medscape.com)
Taurine1
- In felines taurine is considered indispensable and dietary deficiency leads to several clinical problems, including retinal degeneration and developmental abnormalities [ 13 ]. (intechopen.com)
Homocystinuria3
- Deficiency of cystathionine synthase (homocystinuria I) leads to a failure of transsulfuration of precursors of cysteine, an important component of collagen. (mhmedical.com)
- Homocystinuria can be caused by the deficiency of cystathionine synthase. (medscape.com)
- Homocystinuria can be caused by a deficiency in methylenetetrahydrofolate reductase. (medscape.com)
Gene1
- The gene for this deficiency is located on band 21q22.3. (medscape.com)
Dietary1
- Patients in whom the disease does not respond to pyridoxine supplements must be treated with dietary reductions in methionine and with cysteine supplementation. (medscape.com)
Activity1
- The C-terminal domain of cystathionine β-synthase regulates its activity via both intrasteric and allosteric effects and is important for maintaining the tetrameric state of the protein. (wikipedia.org)
Step1
- Crystal Structures of Cystathionine beta-Synthase from Saccharomyces cerevisiae: One Enzymatic Step at a Time. (rhea-db.org)
Results2
- WB results showed that DNLA down-regulated the expression of amyloid-precursor protein (APP), presenilin-1 (PS1), beta-secretase-1 (BACE1), DNA methyltransferase1 (DNMT1), Aß1-40) and Aß1-42) proteins. (bvsalud.org)
- RESULTS: EWASs revealed shared GO annotation pathways associated with increased methylation signatures for several biological processes in response to IRs, including blood circulation, plasma membrane-bounded cell projection organization, cell projection organization, multicellular organismal process, developmental process, and animal organ morphogenesis. (bvsalud.org)
Effects1
- Vitamin E deficiency can lead to 1-methylhistidinuria from increased oxidative effects in skeletal muscle. (pathbank.org)
High1
- CONCLUSIONS: IRs generated a variation in the methylation level of a high number of CpG probes with shared biological pathways, including those associated with cell cycle and division, responses to IRs, sustained angiogenesis, tissue invasion, and metastasis. (bvsalud.org)
MTHFR3
- The accumulation of homocysteine and its metabolites is caused by disruption of any of the 3 interrelated pathways of methionine metabolism-deficiency in the cystathionine B-synthase (CBS) enzyme, defective methylcobalamin synthesis, or abnormality in methylene tetrahydrofolate reductase (MTHFR). (medscape.com)
- Conversion of homocysteine back to methionine, catalyzed by MTHFR and methylcobalamin, is termed the remethylation pathway. (medscape.com)
- Vitamin B1 2 is needed in this process, as are the enzymes methionine synthase MTHFR [ 2 , 3 ]. (selfdecode.com)
Remethylation pathway1
- The remethylation pathway comprises 2 intersecting biochemical pathways and results in the transfer of a methyl group (CH 3 ) to homocysteine from methylcobalamin, which receives its methyl group from S-adenosylmethionine (SAM), from 5-methyltetrahydrofolate (an active form of folic acid), or from betaine (trimethylglycine). (medscape.com)
Biochemical2
- Increased concentrations of homocysteine and methionine associated with decreased levels of cysteine and cystathionine are highly indicative of CH. However, such measurements are not routinely carried out and diurnal fluctuations of amino acid levels may lead to false-negative results, so it may be necessary to repeat biochemical analyses. (symptoma.com)
- It is a critical co-factor for a diverse range of biochemical reactions that regulate basic cellular metabolism, which impact overall physiology. (mdpi.com)
Cofactor1
- It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine: L-serine + L-homocysteine ⇌ {\displaystyle \rightleftharpoons } L-cystathionine + H2O CBS uses the cofactor pyridoxal-phosphate (PLP) and can be allosterically regulated by effectors such as the ubiquitous cofactor S-adenosyl-L-methionine (adoMet). (wikipedia.org)
Vitamin D deficien1
- PURPOSE: The diagnosis of vitamin D deficiency is based on the determination of total plasma 25-hydroxyvitamin D (25-OHD) concentrations, but the regulation of vitamin D 25-hydroxylation is not a major consideration and very little information is available on this activity. (bvsalud.org)
Regulates1
- The C-terminal domain of cystathionine β-synthase regulates its activity via both intrasteric and allosteric effects and is important for maintaining the tetrameric state of the protein. (wikipedia.org)
Metabolic1
- Simplified picture showing homocysteine involvement in different metabolic pathways, as well as the role of vitamins B-6, B-12, and folate as a co-factors in this pathway. (medscape.com)
Autosomal1
- It is inherited in an autosomal recessive manner and is caused by cystathionine β-synthase deficiency. (symptoma.com)
Homocysteine levels2
- Higher homocysteine levels can indicate a deficiency of these vitamins [ 1 ]. (selfdecode.com)
- Apart from vitamin deficiency, higher homocysteine levels have been linked to heart disease, cognitive dysfunction, and dementia. (selfdecode.com)
Pyridoxine1
- Patients in whom the disease does not respond to pyridoxine supplements must be treated with dietary reductions in methionine and with cysteine supplementation. (medscape.com)
Amino acids1
- Moreover, the transsulfuration pathway is the only pathway capable of removing sulfur-containing amino acids under conditions of excess. (wikipedia.org)
Betaine1
- Betaine is a naturally occurring modified form of glycine that aids in the transsulfuration pathways converting homocysteine to methionine. (nih.gov)
Diagnosis2
- Guidelines for the diagnosis and management of cystathionine β-synthase deficiency have been published in 2016 [1]. (symptoma.com)
- The activity of cystathionine β-synthase can be determined in fibroblasts, but this is a rather cumbersome approach to diagnosis. (symptoma.com)
Levels3
- Typically, plasma levels of homocysteine and methionine are elevated while cysteine is decreased. (nih.gov)
- CH is associated with significantly increased serum levels of homocysteine and methionine and low concentrations of cysteine. (symptoma.com)
- The measurement of serum concentrations of homocysteine, methionine, and cysteine is strongly recommended in patients presenting with developmental delay , marfanoid habitus , ectopia lentis , progressive myopia , and other symptoms suggestive of CH. Cystathionine levels may also be assessed. (symptoma.com)
Common1
- Other names in common use include: β-thionase, cysteine synthase, L-serine hydro-lyase (adding homocysteine), methylcysteine synthase, serine sulfhydrase, and serine sulfhydrylase. (wikipedia.org)