Effect of 5-aminolevulinic acid synthesis deficiency on expression of other enzymes of heme pathway in yeast

Abstract

Some enzymes of the heme pathway have been analysed in the nuclear mutant strains cat11 ( hemA-2 ) and cat7 ( hemA-1 ) of Saccharomyces cerevisiae , both in the rho + and rho − states, and in the mutant ole3 ( ole3 , rho + ) already described. The mutation leading to the absence of 5-aminolevulinic acid (ALA) synthase activity and to cytochrome deficiency was not expressed in cat11 rho + , and only partly in cat7 rho + . The rho − mutation unmasked the defects associated with the hemA mutations. When expressed, in ole3, cat11 rho − and cat7 rho − , the absence of ALA (and heme) synthesis led to a total loss of uroporphyrinogen I synthase activity and to an important increase of coproporphyrinogen III oxidase activity. Genetic analysis showed that hemA-1 and ole3 are two different unlinked loci.