Homocysteine Lauren Moore C

What is Homocysteine? IUPAC name is 2-Amino-4-sulfanylbutanoic acid. Homocysteine is an alpha-amino acid. It is closely related to the amino acid cysteine, differing in one methylene group. Biosynthesised from methionine. Can be converted back to methionine or to cysteine.

Source Homocysteine is not part of our diet, it is created as a by-product of digestion. Protein is metabolized to produce methionine. Methionine is then further broken down to produce homocysteine. Homocysteine can then be converted to cysteine if vitamins B6 is present.

Biosynthesis of Homocysteine Source:

Function Homocysteine is a precursor to the amino acid cysteine. Cysteine plays roles in protein structure within the body, in protein folding and cross linking. B vitamins are necessary within the body to convert homocysteine to cysteine for use.

High Levels of Homocysteine Hyperhomocyteinemia. 15 µmol/L High levels occur within the body when levels of B vitamins are low. Hyperhomocysteinemia is a risk factor for thrombosis, cardiovascular disease. Inhibits formation of collagen, elastin and proteoglycans. Links to Alzheimer's Disease, diabetes, hypertension, and fracture risk in the elderly.

Testing A blood test is used to test for high levels of homocysteine. The test helps to ID vitamin B12 and folic acid deficiency.

Reference Values Age 0-30 years: µmol/L Age years: µmol/L (males); µmol/L (females) Age >59 years: µmol/L

Other Influencing Factors Other factors can affect homocysteine levels, apart from vitamin B deficiency; Age Sex Other conditions or diseases, such as homocystinuria, kidney disease, hypothyroidism, Alzheimer's disease, or certain cancers. High alcohol consumption.

References Mao X, Xing X, Xu R, Gong Q, He Y, Li S, Wang H, Liu C, Ding X, Na R, Liu Z, Qu Y, 2016, Folic Acid and Vitamins D and B12 Correlate With Homocysteine in Chinese Patients With Type-2 Diabetes Mellitus, Hypertension, or Cardiovascular Disease, Medicine, Vol. 95(6), (accessed Feb 11, 2016). Miller JW, Nadeau MR, Smith D, Selhub J, 1994, Vitamin B-6 deficiency vs folate deficiency: comparison of responses to methionine loading in rats, The American Journal of Clinical Nutrition 59 (5): 1033–9. Morris MS, 2003, Homocysteine and Alzheimer's disease, Lancet neurology 2 (7), 425–8. National Center for Biotechnology Information, PubChem Compound Database; CID=439155, (accessed Feb. 11, 2016).