2392 Nephrol Dial Transplant (1996) 11: Editorial Comments Hyperhomocyst(e)inaemia in renal failure—what are the implications?

Homocysteine is a sulphur-containing amino acid that results from demethylation of dietary methionine [1]. It is present in plasma, and its plasma levels are thought to be a reflection of intracellular metabolism and cellular export of homocysteine [1]. Plasma homo-cysteine exists in two forms: 98 % as oxidized (disulph-ide) form, and 2 % or even less as reduced (sulphydryl) form. A major fraction of oxidized homocysteine (about 70-80%) is associated with plasma proteins, probably linked to albumin by a disulphide bridge [1]. The remainder of oxidized homocysteine components (homocystine or homocysteine-cysteine) are non-protein-bound or free [1]. The sum of all homocysteine species in plasma (reduced, free, and protein-bound) is referred to as total homocyst(e)ine. Total homocys