S-Adenosyl methionine

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S-Adenosyl methionine
Names
Systematic IUPAC name
(2S)-2-Amino-4-[(S)-{[(2S,3S,4R,5R)-5-(4-amino-9H-purin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl}methylsulfaniumyl]butanoate
Other names
S-Adenosyl-L-methionine; SAM-e; SAMe, AdoMet, Heparab (India), ademethionine
Identifiers
3D model (
JSmol
)
ChEMBL
ChemSpider
ECHA InfoCard
100.045.391 Edit this at Wikidata
KEGG
MeSH S-Adenosylmethionine
UNII
  • InChI=1S/C15H22N6O5S/c1-27(3-2-7(16)15(24)25)4-8-10(22)11(23)14(26-8)21-6-20-9-12(17)18-5-19-13(9)21/h5-8,10-11,14,22-23H,2-4,16H2,1H3,(H2-,17,18,19,24,25)/p+1/t7?,8-,10-,11-,14-,27?/m1/s1 checkY
    Key: MEFKEPWMEQBLKI-YDBXVIPQSA-O checkY
  • InChI=1/C15H22N6O5S/c1-27(3-2-7(16)15(24)25)4-8-10(22)11(23)14(26-8)21-6-20-9-12(17)18-5-19-13(9)21/h5-8,10-11,14,22-23H,2-4,16H2,1H3,(H2-,17,18,19,24,25)/p+1/t7?,8-,10-,11-,14-,27?/m1/s1
    Key: MEFKEPWMEQBLKI-NNGIMXIKBF
  • O=C(O)C(N)CC[S+](C)C[C@H]3O[C@@H](n2cnc1c(ncnc12)N)[C@H](O)[C@@H]3O
Properties
C15H22N6O5S
Molar mass 398.44 g·mol−1
Pharmacology
A16AA02 (WHO)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

S-Adenosyl methionine (SAM), also known under the commercial names of SAMe, SAM-e, or AdoMet, is a common

methionine adenosyltransferase. SAM was first discovered by Giulio Cantoni in 1952.[1]

In

ethylene, an important plant hormone and signaling molecule.[3]

Structure

S-Adenosyl methionine consists of the adenosyl group attached to the sulfur of methionine, providing it with a positive charge. It is synthesized from ATP and methionine by S-Adenosylmethionine synthetase enzyme through the following reaction:

ATP + L-methionine + H2O
diphosphate
+ S-adenosyl-L-methionine

The sulfonium functional group present in S-adenosyl methionine is the center of its peculiar reactivity. Depending on the enzyme, S-adenosyl methionine can be converted into one of three products:

  • adenosyl radical, which converts to deoxyadenosine (AdO): classic rSAM reaction, also cogenerates methionine
  • S-adenosyl homocysteine
    , releasing methyl radical
  • methylthioadenosine
    (SMT), homoalanine radical

Biochemistry

SAM cycle

The SN2-like methyl transfer reaction. Only the SAM cofactor and cytosine base are shown for simplicity.

The reactions that produce, consume, and regenerate SAM are called the SAM cycle. In the first step of this cycle, the SAM-dependent

cobalamin-dependent (EC 2.1.1.13) or cobalamin-independent (EC 2.1.1.14)). This methionine can then be converted back to SAM, completing the cycle.[5] In the rate-limiting step of the SAM cycle, MTHFR (methylenetetrahydrofolate reductase) irreversibly reduces 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate.[6]

Radical SAM enzymes

A large number of enzymes cleave SAM reductively to produce radicals:

iron-sulfur cluster at their active sites.[7]
Most enzymes with this capability share a region of sequence homology that includes the motif CxxxCxxC or a close variant. This sequence provides three cysteinyl thiolate ligands that bind to three of the four metals in the 4Fe-4S cluster. The fourth Fe binds the SAM.

The radical intermediates generated by these enzymes perform a wide variety of unusual chemical reactions. Examples of radical SAM enzymes include

tRNA modification, lipid metabolism, etc. Some radical SAM enzymes use a second SAM as a methyl donor. Radical SAM enzymes are much more abundant in anaerobic bacteria than in aerobic organisms. They can be found in all domains of life and are largely unexplored. A recent bioinformatics study concluded that this family of enzymes includes at least 114,000 sequences including 65 unique reactions.[8]

Deficiencies in radical SAM enzymes have been associated with a variety of diseases including

amyotrophic lateral sclerosis, and increased viral susceptibility.[8]

Polyamine biosynthesis

Another major role of SAM is in polyamine biosynthesis. Here, SAM is decarboxylated by adenosylmethionine decarboxylase (EC 4.1.1.50) to form S-adenosylmethioninamine. This compound then donates its n-propylamine group in the biosynthesis of polyamines such as spermidine and spermine from putrescine.[9]

SAM is required for cellular growth and repair. It is also involved in the biosynthesis of several hormones and neurotransmitters that affect mood, such as

epinephrine. Methyltransferases are also responsible for the addition of methyl groups to the 2′ hydroxyls of the first and second nucleotides next to the 5′ cap in messenger RNA.[10][11]

Therapeutic uses

Osteoarthrtitis pain

As of 2012, the evidence was inconclusive as to whether SAM can mitigate the pain of osteoarthritis; clinical trials that had been conducted were too small from which to generalize.[12]

Liver disease

The SAM cycle has been closely tied to the liver since 1947 because people with

animal models suggest that SAM might be useful to treat various liver diseases, as of 2012 SAM had not been studied in any large randomized placebo-controlled clinical trials that would allow an assessment of its efficacy and safety.[14][15]

Depression

A 2016 Cochrane review concluded that for major depressive disorder, "Given the absence of high quality evidence and the inability to draw firm conclusions based on that evidence, the use of SAMe for the treatment of depression in adults should be investigated further."[16]

A 2020 systematic review found that it performed significantly better than placebo, and had similar outcomes to other commonly used antidepressants (imipramine and escitalopram).[17]

Anti-cancer treatment

SAM has recently been shown to play a role in epigenetic regulation. DNA methylation is a key regulator in epigenetic modification during mammalian cell development and differentiation. In mouse models, excess levels of SAM have been implicated in erroneous methylation patterns associated with diabetic neuropathy. SAM serves as the methyl donor in cytosine methylation, which is a key epigenetic regulatory process.[18] Because of this impact on epigenetic regulation, SAM has been tested as an anti-cancer treatment. In many cancers, proliferation is dependent on having low levels of DNA methylation. In vitro addition in such cancers has been shown to remethylate oncogene promoter sequences and decrease the production of proto-oncogenes.[19] In cancers such as colorectal cancer, aberrant global hypermethylation can inhibit promoter regions of tumor-suppressing genes. Contrary to the former information, colorectal cancers (CRCs) are characterized by global hypomethylation and promoter-specific DNA methylation.[20]

Pharmacokinetics

Oral SAM achieves peak plasma concentrations three to five hours after ingestion of an enteric-coated tablet (400–1000 mg). The half-life is about 100 minutes.[21]

Availability in different countries

In Canada, the UK,

Dietary Supplement Health and Education Act was passed in 1994.[24]

It was introduced as a prescription drug in Italy in 1979, in Spain in 1985, and in Germany in 1989.[24] As of 2012, it was sold as a prescription drug in Russia, India, China, Italy, Germany, Vietnam, and Mexico.[15]

Adverse effects

Gastrointestinal disorder,

dyspepsia and anxiety can occur with SAM consumption.[21] Long-term effects are unknown. SAM is a weak DNA-alkylating agent.[25]

Another reported side effect of SAM is insomnia; therefore, the supplement is often taken in the morning. Other reports of mild side effects include lack of appetite, constipation, nausea, dry mouth, sweating, and anxiety/nervousness, but in placebo-controlled studies, these side effects occur at about the same incidence in the placebo groups.[medical citation needed]

Interactions and contraindications

Taking SAM at the same time as some drugs may increase the risk of

meperidine (Demerol), pentazocine (Talwin), and tramadol (Ultram).[26]

SAM can also interact with many antidepressant medications — including

levodopa for Parkinson's disease.[27] SAM can increase the risk of manic episodes in people who have bipolar disorder.[27]

Toxicity

A 2022 study concluded that SAMe could be toxic. Jean-Michel Fustin of

laboratory mice, causing harm to health, and in in vitro tests on human cells.[28][22]

See also

References

External links