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homocysteine ho·mo·cys·te·ine (hō'mə-sĭs'tə-ēn', -ĭn, -tē-)
An amino acid that is a homologue of cysteine, is produced by the demethylation of methionine, and forms a complex with serine that metabolizes to produce cysteine and homoserine.
An amino acid used normally by the body in cellular metabolism and the manufacture of proteins. Elevated concentrations in the blood are thought to increase the risk for heart disease by damaging the lining of blood vessels and increasing the risk of blood clot formation. High homocysteine levels are associated with certain vitamin deficiencies and metabolic disorders. Chemical formula: C4H9NO2S.