High production of sulfide in coenzyme Q deficient fission yeast

We have constructed coenzyme Q deficient fission yeast strains by deletion of ten different genes, all of which are absolutely required for the CoQ10 biosynthesis. We found that sulfide was highly accumulated in all fission yeast CoQ10 deficient mutants. In fission yeast sulfide is required for the synthesis of cysteine and homocysteine which are catalyzed by cysteine synthase (Cys1a) and homocysteine synthase (Met17), respectively. To better understand the relation between sulfide metabolism and coenzyme Q, we expressed cys1a, met17 and hmt2, which encodes sulfide-quinone oxidoreductase, in CoQ10 deficient mutants and other mutants, and measured the level of sulfide. Although expression of cys1a and met17 lowered sulfide production in CoQ10 deficient mutants, hmt2 did not lower the level of sulfide, because Hmt2 requires coenzyme Q for its function. In contrast, expression of hmt2 lowered sulfide production in cys1a and met17 mutants. These and other results indicate that coenzyme Q is important for sulfide oxidation through sulfide-quinone oxidoreductase to detoxify excess sulfide in fission yeast.