| Abstract: | Levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, was used to inhibit cytochrome biosynthesis in growing yeast cells. In Saccharomyces cerevisiae the antimetabolite acts by inhibiting delta-aminolevulinic acid dehydratase in vivo, causing an accumulation of intracellular delta-aminolevulinic acid and simultaneous decreases in all classes of mitochondrial cytochromes. Changes in cellular cytochrome content with increasing levulinic acid concentration suggested the existence of different regulatory patterns in S. cerevisiae and Candida utilis. In C. utilis, cytochrome a.a3 formation is very resistant to the antimetabolite action of levulinic acid. In this aerobic yeast, cytochrome c+c1 is the most sensitive to levulinic acid, and cytochrome b exhibits intermediate sensitivity. |
