Methionine

Methionine is an essential, nonpolar proteinogenic amino acid containing a sulfur atom. It can be converted to cysteine.

Methionine molecule

Metabolism

As an essential amino acid, methionine cannot be synthesized and must be obtained from the diet.

Convert to SAM

S-adenosylmethionine, or active methionine, is a nucleoside capable of methylating other substances and is therefore essential in many metabolic pathways (choline, creatine, adrenaline, ...). This property is due to the presence of a positively charged sulfur atom. The synthesis of SAM from methionine requires ATP and is catalyzed by the appropriate transferase.

Conversion to Cysteine ​​

The starting substance of conversion to cysteine ​​is S-adenosylmethionine. This is converted into S-adenosylhomocysteine ​​by splitting off the methyl, which then changes into homocysteine. After its fusion with serine, cystathion is formed. It disintegrates immediately, but the sulfur atom remains on the serine skeleton. Homocysteine ​​is left to homoserine, which is converted to succinyl-CoA via propionyl-CoA.

Task in translation

As methionine is encoded by the initiation codon AUG, it forms the cap at the N-terminus of each newly synthesized peptide. However, this is usually removed as part of post-translational modifications.

Links

• ws: Methionin

Related Articles

• Amino Acids

References

• KIDNEY, Miroslav – STOKLASOVÁ, Alena – CERMAN, Jaroslav. Biochemistry for medical students. 2. edition. Prague : Karolinum, 2009. ISBN 978-80-246-1414-4.

• MURRAY, Robert Kincaid – BOTHAM, Kathleen M, et al. Harper's Illustrated Biochemistry. 5. edition. Prague : Galen, 2012. ISBN 978-80-7262-907-7.

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