Signaling pathways of hyperhomocystenemia and oxidative stress

Homocysteine (HCY) is a non-protein-forming, sulfur amino acid whose metabolism is at the intersection of two metabolic pathways, remethylation and trans-sulfuration pathways. HCY is characterized by its chemical tendency to promote oxidative stress and cellular toxicity. Three major forms of homocysteine species exist in human blood circulation; albumin-bound, disulfide from, and sulfhydryl form. Current laboratory methods detect the presence of all three forms and report this as total homocysteine concentration [1]. Normal homocysteine concentrations range from 5-15 μmol/L, intermediately elevated homocysteine levels are between 31 and 100 μmol/L, while severely elevated levels are >100 μmol/L [1].