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

Results of in vitro experiments carried out in water at 25 degreesC and at pH 7.56 proved that NADPH in the presence of yeast glutathione reductase di d not react with 1,2-dithiole-3-thiones and 1,2-dithiole-3-ones. On the oth er hand, 3-methylthiodithiolylium ions did react in these conditions. The r eaction 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 (K-m = 2.6 10(-5) mol .l(-1)). All these results raise the question of a possible in vivo methylation (or alk ylation) of dithiolethiones occurring prior to any other reductive biochemi cal process they may undergo. They also raise the question of the very exis tence (or in any case the generalization) of a reductive metabolism of dith iolethiones. (C) 2000 Academic Press.