Homocystine is the oxidized form of homocysteine. A substance is oxidized when it undergoes the process of oxidation. I.e the addition of oxygen or any electronegative elements or the removal of hydrogen or any electropositive element.
Homocystine is a dipeptide consisting of two homocysteine molecules joined by a disulfide bond. A dipeptide is a molecule that consists of two amino acids joined together by a peptide bond.
Homocystine occurs only transiently before being reduced to homocysteine and converted to the harmless cystathionine via a vitamin B6-dependent enzyme. Homocystine and homocysteine-cysteine mixed disulfides account for >98% of total homocysteine in plasma from healthy individuals.
Homocystine has been shown to stereospecifically induce endothelial nitric oxide synthase-dependent lipid peroxidation in endothelial cells, thereby inducing a vascular cell type-specific oxidative stress. This vascular stress is associated with atherothrombotic cardiovascular disease. High levels of homocysteine (and homocysteine) can be found in individuals suffering from homocystinura due to cystathionine synthase deficiency.
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