Modified uroporphyrinogen decarboxylase activity in a yeast mutant which mimics porphyria cutanea tarda.
The isolation of a new mutant Sm1 strain of yeast, Saccharomyces cerevisiae, is described: this strain was partially defective in haem formation and accumulated large amounts of Zn-porphyrins. Genetic analysis showed that the porphyrin accumulation was under the control of a single nuclear recessive mutation. Biochemical analysis showed that the main porphyrins accumulated in the cells were uroporphyrin and heptacarboxyporphyrin, mostly of the isomer-III type. The excreted porphyrins comprised mainly dehydroisocoproporphyrin. Analysis of uroporphyrinogen decarboxylase activity in the cell-free extract revealed a 70-80% decrease of activity in the mutant and showed that the relative rates of the different decarboxylation steps were modified with the mutant enzyme. A 2-3-fold increase in 5-aminolaevulinate synthase activity was measured in the mutant. The biochemical characteristics of the Sm1 mutant are very similar to those described for porphyria cutanea tarda.[1]References
- Modified uroporphyrinogen decarboxylase activity in a yeast mutant which mimics porphyria cutanea tarda. Rytka, J., Bilinski, T., Labbe-Bois, R. Biochem. J. (1984) [Pubmed]
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