Redox status and protein binding of plasma homocysteine and other aminothiols in patients with hyperhomocysteinemia due to cobalamin deficiency.
We determined reduced, oxidized, and protein-bound homocysteine, cysteine, and cysteinylglycine in plasma from 13 patients with hyperhomocysteinemia (total homocysteine in the range 30.6-159.8 mumol/L) due to cobalamin deficiency. Reduced homocysteine (means +/- SD: 1.87 +/- 2.06 mumol/L) was markedly above normal (0.24 +/- 0.12 mumol/L) in most patients, and the reduced fraction increased as an exponential function of the total homocysteine concentration. The ratio of reduced homocysteine to total homocysteine was positively correlated with the reduced-total ratio for cysteine and cysteinylglycine, suggesting redox equilibrium between different aminothiol species. The free oxidized and the protein-bound forms of homocysteine account for most of the homocysteine in plasma of these patients. The amount of protein-bound homocysteine was negatively correlated with the concentrations of both protein-bound cysteine and cysteinylglycine, indicating displacement of these aminothiols by homocysteine.
Mansoor
M A
MA
Department of Pharmacology and Toxicology, University of Bergen, Haukeland Hospital, Norway.
Ueland
P M
PM
Svardal
A M
AM
D000368:Aged; D001798:Blood Proteins / Q000378:metabolism*; D003545:Cysteine / Q000097:blood; D005260:Female; D005998:Glycine / Q000097:blood; D006454:Hemoglobins / Q000032:analysis; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D011485:Protein Binding; D014806:Vitamin B 12 Deficiency / Q000097:blood*
D001798:Blood Proteins; D006454:Hemoglobins; D006710:Homocysteine; D003545:Cysteine; D005998:Glycine