TRANSFER OF ARSENITE FROM GLUTATHIONE TO DITHIOLS - A MODEL OF INTERACTION

The interactions of arsenate and arsenite with meso-2,3-dimercaptosucc inic acid (DMSA) have been characterized using carbon-13 nuclear magne tic resonance. These studies show that DMSA reduces arsenate to arseni te and complexes arsenite. Monitoring the carbon-13 signals of complex ed DMSA and liberated glutathione shows that DMSA readily extracts ars enite from a (glutathione)3-arsenite complex, proving the affinity of arsenite for dithiols is greater than that for monothiols. Competition between DMSA (vicinal thiols) and dithioerythritol (1,4-dimercapto-2, 3-butanediol) for binding of arsenite indicates that the binding affin ity is inversely related to the distance between the two thiol groups. On the basis of these findings, a model for the interaction of arseni c with mono- and dithiol-containing molecules is proposed.