S-adenosylmethionine cycle
Definition
Target type: biologicalprocess
A cyclic series of interconversions involving S-adenosylmethionine, S-adenosyl-L-homocysteine, L-cysteine, and L-methionine. Couples utilization of the methyl group of SAM with recycling of the homocysteinyl group and regeneration of methionine. [GOC:mah, MetaCyc:PWY-5041]
The S-adenosylmethionine (SAM) cycle is a fundamental metabolic pathway crucial for numerous cellular processes. It begins with the synthesis of SAM from methionine and ATP, catalyzed by the enzyme methionine adenosyltransferase (MAT). SAM serves as a universal methyl donor in a wide range of methylation reactions, including DNA, RNA, proteins, and lipids. These methylation events regulate gene expression, protein function, and cellular signaling. After donating its methyl group, SAM is converted to S-adenosylhomocysteine (SAH), a potent inhibitor of most methyltransferases. SAH is then hydrolyzed to homocysteine and adenosine by SAH hydrolase. Homocysteine can be remethylated back to methionine by tetrahydrofolate reductase (THF reductase) or incorporated into cysteine via the transsulfuration pathway. The cycle is tightly regulated to ensure optimal SAM levels and proper cellular function. Defects in the SAM cycle can lead to various diseases, including homocystinuria, neurodevelopmental disorders, and cancer.'
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Proteins (1)
| Protein | Definition | Taxonomy |
|---|---|---|
| Adenosylhomocysteinase | An adenosylhomocysteinase that is encoded in the genome of human. [PRO:DNx, UniProtKB:P23526] | Homo sapiens (human) |
Compounds (17)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| 3-deazaadenosine | 3-deazaadenosine: RN given refers to parent cpd. | ||
| ribavirin | Rebetron: Rebetron is tradename | 1-ribosyltriazole; aromatic amide; monocarboxylic acid amide; primary carboxamide | anticoronaviral agent; antiinfective agent; antimetabolite; antiviral agent; EC 2.7.7.49 (RNA-directed DNA polymerase) inhibitor |
| adenosine | quinquefolan B: isolated from roots of Panax quinquefolium L.; RN not in Chemline 10/87; RN from Toxlit | adenosines; purines D-ribonucleoside | analgesic; anti-arrhythmia drug; fundamental metabolite; human metabolite; vasodilator agent |
| aristeromycin | aristeromycin: RN given refers to (1R-(1alpha,2alpha,3beta,5alpha)-isomer | ||
| illimaquinone | illimaquinone: structure given in first source; isolated from the Red Sea sponge Smenospongia; inhibits the RNase H. activity of HIV-1 reverse transcriptase | monohydroxy-1,4-benzoquinones; prenylquinone | metabolite |
| 3-deazaaristeromycin | 3-deazaaristeromycin: antagonist of S-adenosylhomocysteinase | ||
| neplanocin a | neplanocin A: neplanocins are antitumor antibiotics & carbocyclic analogs of purine nucleosides from Ampullarilla regularis A11079; see also neplanocin B, neplanocin C, neplanocin D & neplanocin F; structure in first source; a potent inhibitor of S-adenosylhomocysteine hydrolase | ||
| 3-deazaneplanocin | 3-deazaneplanocin: S-adenosylhomocysteine hydrolase antagonist | ||
| 9-(2',3'-dihydroxycyclopentan-1'-yl)adenine | 9-(2',3'-dihydroxycyclopentan-1'-yl)adenine: inhibitor of S-adenosylhomocysteine hydrolase; structure given in first source | ||
| adenosine-5'-carboxylic acid | purine nucleoside | ||
| 5'-n-methylcarboxamideadenosine | 5'-N-methylcarboxamideadenosine: RN given refers to (beta-D)-isomer | ||
| 5'-noraristeromycin | 5'-noraristeromycin: structure given in first source | ||
| adenosine-5'-carboxaldehyde | 5'-dehydroadenosine : A member of the class of adenosines that is 5'-dehydro derivative of adenosine. adenosine-5'-carboxaldehyde: potent inhibitor of S-adenosyl-L-homocysteine hydrolase; structure given in first source | adenosines | |
| 9-(2',3'-dihydroxycyclopent-4'-enyl)adenine | |||
| 5'-amino-5'-deoxyadenosine | |||
| guanosine | ribonucleoside : Any nucleoside where the sugar component is D-ribose. | guanosines; purines D-ribonucleoside | fundamental metabolite |
| inosine | inosines; purines D-ribonucleoside | Escherichia coli metabolite; human metabolite; mouse metabolite; Saccharomyces cerevisiae metabolite |