On the reduction of dithiolethiones and dithiolylium ions by NADPH and glutathione reductase.

Results of in vitro experiments carried out in water at 25 degrees C and at pH 7.56 proved that NADPH in the presence of yeast glutathione reductase did not react with 1,2-dithiole-3-thiones and 1,2-dithiole-3-ones. On the other hand, 3-methylthiodithiolylium ions did react in these conditions. The reaction was identified and methyl 3-mercaptopropenedithioate resulting from a two-electron reduction process was obtained. A kinetic scheme consisting in a biordered mechanism has been found (Km = 2.6 10(-5) mol x l(-1)). All these results raise the question of a possible in vivo methylation (or alkylation) of dithiolethiones occurring prior to any other reductive biochemical process they may undergo. They also raise the question of the very existence (or in any case the generalization) of a reductive metabolism of dithiolethiones.