methionine metabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways involving methionine (2-amino-4-(methylthio)butanoic acid), a sulfur-containing, essential amino acid found in peptide linkage in proteins. [GOC:jl, ISBN:0198506732]

Methionine metabolism is a complex and essential biological process that involves the synthesis, degradation, and utilization of the amino acid methionine. This process is crucial for various cellular functions, including protein synthesis, methylation reactions, and the production of essential metabolites like cysteine and S-adenosyl methionine (SAM).

**Methionine Synthesis:**

- Methionine is synthesized from homocysteine in a one-step reaction catalyzed by the enzyme tetrahydrofolate reductase.
- This reaction requires tetrahydrofolic acid (THF) as a cofactor.

**Methionine Degradation:**

- The degradation of methionine begins with its conversion to S-adenosyl methionine (SAM) by the enzyme methionine adenosyltransferase.
- SAM is the primary methyl donor in the body and is involved in a wide range of methylation reactions, including DNA methylation, histone methylation, and the synthesis of neurotransmitters.
- After donating its methyl group, SAM is converted to S-adenosyl homocysteine (SAH), which is then hydrolyzed to homocysteine and adenosine.

**Homocysteine Metabolism:**

- Homocysteine can be remethylated to methionine by the enzymes tetrahydrofolate reductase or betaine-homocysteine methyltransferase.
- Alternatively, homocysteine can be converted to cysteine by the enzyme cystathionine beta-synthase.

**Cysteine Synthesis:**

- Cysteine is an essential amino acid that is not directly synthesized from methionine but is produced from homocysteine via the transsulfuration pathway.

**Regulation of Methionine Metabolism:**

- The regulation of methionine metabolism is complex and involves multiple factors, including dietary intake, enzyme activity, and cellular demand.
- For example, high levels of SAM inhibit the synthesis of SAM and stimulate its degradation.

**Clinical Relevance:**

- Methionine metabolism is crucial for maintaining overall health.
- Deficiencies or abnormalities in methionine metabolism can lead to a range of health problems, including homocystinuria, cardiovascular disease, and neurodevelopmental disorders.

In summary, methionine metabolism is a vital biological process that encompasses a series of reactions involving synthesis, degradation, and utilization of methionine. This process plays a critical role in protein synthesis, methylation reactions, and the production of essential metabolites like cysteine and SAM. Dysregulation of methionine metabolism can have significant implications for human health.'
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Proteins (3)

Compounds (4)