Iron uptake by the yeast Saccharomyces cerevisiae: involvement of a reduction step.

Among several parameters affecting the rate and amount of iron uptake by Saccharomyces cerevisiae, the oxidation state of iron appeared to be determinant. Iron presented as Fe(II) was taken up faster than Fe(III) and the kinetic parameters were different. Iron was taken up by the cells from different ferric chelates, at rates that did not depend on their stability constants, and uptake was strongly inhibited by an iron(II)-trapping reagent like ferrozine. Iron was physiologically reduced by a transplasmamembrane redox system, which was induced in iron-deficient conditions. We propose that iron must be reduced to be taken up by the cells in the same way as other divalent cations.