Methionine metabolism pathway enzyme

The term "Methionine metabolism pathway enzymes" refers collectively to a set of **enzymes that catalyze the synthesis, utilization, recycling, and degradation of the essential amino acid methionine**. These include but are not limited to: **Key enzymes** in this network include: * **Methionine adenosyltransferase:** Converts methionine into S-Adenosylmethionine (SAM), a universal methyl donor critical for DNA/RNA/protein/lipid methylation reactions[1][2]. * **Methionine synthase:** Catalyzes the remethylation of homocysteine back to methionine using vitamin B12 as a cofactor; links folate and one-carbon cycles[1][2]. * **Betaïne-homocysteïne methyltransferase:** Alternative route for remethylating homocysteïne using betaine as a donor—predominantly active in liver/kidney[2]. * **S-Adenosylhomocysteinase:** Hydrolyzes SAH into adenosyne and homocycteïne; prevents feedback inhibition on other methyltransferases[2]. * **Cystathione β-synthase & cystathione γ-synthase/β–lyase:** Divert excess homocycteïne into transsulfuration pathway for cysteine/glutathione production—important for antioxidant defense and sulfur homeostasis[3][5]. These enzymes collectively regulate cellular pools of SAM/methioinine/homocycteïne/cystéíne. Their activity is tightly controlled by nutritional status (folate/B12/betaîne), feedback from metabolites like SAM/SAH/homocycteïne itself, transcriptional regulation according to cell growth needs or stress responses—and their dysfunction is implicated in cancer progression via altered epigenetic marks/methyl group supply; cardiovascular/neurodegenerative diseases via hyperhomocycteïnemia; inherited metabolic disorders such as classic/mild forms of *homocytinuria*, *methylmalonic acidemia*, etc.[5][6]. Because "Methioinine metabolism pathway enzymes" is not a single molecular entity but rather an umbrella term covering multiple distinct proteins/enzymes within an interconnected biochemical network—it is considered an incorrect target name when specificity at the individual protein level is required. > The “methioinine cycle” serves as a hub for various metabolic pathways... Key regulatory points include MAT [methioinine adenosyltransferasé], MS [méthioinine synthasé], BHMT [betaîne-homocyctéinè méthyltansferasé], CBS [cystathione β-synthasé] among others. Proper function ensures optimal cellular growth/proliferatíon/DNA-methýlation/redox balance.[1][2] In summary: This entry describes an important class/family/network rather than one specific druggable target molecule.

Other names

Methionine cycle enzymeOne-carbon metabolism enzymeSulfur amino acid metabolism enzymeEnzymes of methionine biosynthesis and degradation

Inhibition or modulation of key enzymes alters methyl group availability and homocysteine levels. - For example, inhibition of methionine adenosyltransferase reduces S-Adenosylmethionine synthesis[1][2]. - Supplementation with vitamin B12 or betaine enhances remethylation of homocysteine to methionine[2].