Redox Status of Homocysteine
Homocysteine in plasma exists in different forms, including the major protein-bound fraction (approx 65%), free oxidized fraction (approx 30%), and reduced homocysteine, which is present in only trace amounts (1.5 - 4%). Because homocysteine in blood is rapidly oxidized, and is associated with plasma proteins, assessment of its redox status and protein binding requires immediate derivatization of the reduced homocysteine and separation of the free and bound forms. It is thought that the redox status of homocysteine may differ between patient groups and be linked with its atherogenic effects. Reduced homocysteine acts as a pro-oxidant in vitro and may be the atherogenic agent.
In patients with early-onset peripheral vascular disease, levels of reduced, oxidized, and protein-bound homocysteine are reportedly elevated whereas in patients with hyperhomocysteinamia because of cobalamin deficiency and in patients infected with human immunodeficiency virus reduced homocysteine concentrations are markedly above normal.
