Characterization of two mutant strains of Saccharomyces cerevisiae deficient in coproporphyrinogen III oxidase activity.

Two new haem-deficient mutants of Saccharomyces cerevisiae were isolated on the basis of their catalase deficiency. Mutant H11 accumulated and excreted coproporphyrin III and was completely deficient in haem; the cell-free extract had no coproporphyrinogen oxidase activity. Mutant H12 accumulated uroporphyrin to coproporphyrin III and excreted coproporphyrin III, and contained a small amount of haem; the cell-free extract had a residual coproporphyrinogen oxidase activity. The two mutations were allelic and the mutant phenotypes were under the control of a single, recessive nuclear gene.