HEMIN DEGRADATION IN PRESENCE OF THIOLS AND TRANSITION METAL IONS.

  Hemin degradation by various thiols including cysteine, homocysteine, N-acetylcysteine, glutamyl-cysteinyl-alanine, mercaptoethanol and dithiothreitol, and also the effect of transition metal ions like cobalt(II), copper(II), manganese(II), zinc(II), chromium(III), iron(II) and iron(III) on this degradation have been investigated. Glutathione (GSH) and other thiols have successfully degraded hemin.  Metals like Cobalt(II), Copper(II), Chromium(III) and iron(II) inhibited GSH mediated hemin degradation. However this inhibition was marginally reversed by the addition of metal chelators and diethylenetriaminepentaacetic acid (DTPA). Manganese(II) and zinc(II) were increased the degradation but the DTPA abolished this increase. Iron(III) had no effect on GSH mediated degradation but co-incubation with DTPA resulted a remarkable inhibition. The effect of cobalt(II), manganese(II), Fe(II) and Fe(III) on hemin degradation by homocysteine, dithiothreitol and glutamyl-cysteinyl-alanine showed differences vis-à-vis GSH. In conclusion the results indicate that thiols other than GSH should also be explored for their protective effect on hemin-mediated membrane destabilization by virtue of their hemin degrading ability.   Key Words : Hemin, glutathione, thiols, transition metal ions, RBC membranes.