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Homocysteine is an uncommon amino acid. The molecular formula is HOO=CCH(NH2)(CH2)2SH.


Homocysteine is produced by the hydrolysis of the common amino acid methionine.

Methionine + Water → Homocysteine + Methanol

Homocysteine can also be produced by the hydrolysis of S-adenosyl-L-homocysteine.

S-adenosyl-L-homocysteine + water ↔ adenosine + homocysteine

This reaction is catalyzed by the enzyme S-adenosyl-L-homocysteine hydrolase.[1] This enzyme is involved in normal T-cell and macrophage function.[2]


Elevated levels of serum homocysteine is associated with an increased risk of coronary artery disease.[3] Among individuals with type 2 diabetes elevated plasma homocysteine levels are associated with an increased risk of macroangiopathy and nephropathy.[4] It is unclear if this increased risk is due to the homocysteine itself, the methanol which is produced as a by-product of homocysteine biosynthesis, or some other mechanism which is correlated with homocysteine biosynthesis. Some authors believe that methanol causes arteriosclerosis.[5] Other authors believe that arteriosclerosis is caused by homocysteine via some direct but yet to be explained mechanism.[6]

Chronic infection[edit]

Elevated serum homocysteine levels, in spite of normal dietary methionine intake, may therefore suggest a chronic infection.

See also[edit]


  1. My very best wishes (9 July 2009). "S-adenosyl-L-homocysteine hydrolase, In: Wikipedia". San Francisco, California: Wikimedia Foundation, Inc. Retrieved 2017-01-04.
  2. http://www.ncbi.nlm.nih.gov/pubmed/15640397
  3. http://jama.ama-assn.org/content/274/13/1049.abstract
  4. http://care.diabetesjournals.org/content/23/12/1816.abstract
  5. http://www.medical-hypotheses.com/article/S0306-9877(09)00693-8/abstract
  6. http://jama.ama-assn.org/content/279/5/392.extract

External links[edit]

{{Medicine resources}}{{Phosphate biochemistry}}