Yeast cell cytochrome regulation

A feature of some pterocarpan phytoalexins (e.g., pisatin and glyceollin of pea and soybean, respectively) is their hydroxylation at position 6a, a reaction catalyzed by a microsomal cytochrome P450 monooxygenase.49 50 A cDNA encoding this enzyme was recently characterized from elicited soybean cell cultures.51 The microsomal protein, expressed in yeast cells, catalyzed the stereoselective hydroxylation of (6a/ , lla/ )-3,9-dihydroxypterocarpan to its 6a-hydroxy derivative. It was also demonstrated that the enzyme expression is regulated at the transcriptional level.51... 

Yeast is of exceptional value in the study of cytochrome regulation. It is a facultative anaerobe, and the usual cytochromes disappear under anaerobic conditions. On aeration, cytochrome induction can be demonstrated in the living cell, and the role of oxygen and carbon source, as well as the effect of inhibitors, can be evaluated by a variety of means [19-25], Yeast affords opportunities for genetic analysis and lends itself to studies of the inheritance of nuclear factors governing cytochrome synthesis. Moreover, this organism readily develops a mitochondrial abnormality on treatment with acriflavine, the petite mutation, which permits examination of the role of cytoplasmic inheritance [26]. 

Forsburg, S. L., and L. Guarente, Communication between mitochondria and the nucleus in regulation of cytochrome genes in the yeast Saccharomyces cerevisiae. Ann. Rev. Cell. Biol. 5 153-180, 1989. 

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