ABSTRACT
The yeast Saccharomyces cerevisiae, a “small” eukaryotic, unicellular organism, is well suited to studies on the relationships between iron metabolism and protoheme synthesis. It is stable in both haploid and diploid states and is easy to handle both biochemically and genetically. This chapter begins with an analysis of ferrochelatase function in vivo in S. cerevisiae. Ferrochelatase provides protoheme for the various apocytochromes and apohemoproteins that require it as a prosthetic group for their biological functions. The heme biosynthetic pathway in S. cerevisiae has the same eight enzymic steps as in mammalian cells, with the same subcellular compartmentation, except that the coproporphyrinogen oxidase is in the cytosol, whereas it is in the mitochondrial intermembrane space in mammalian cells. The heme made in the mitochondria is used in the processing and assembly of holohemoproteins located in different cellular compartments. Heme must also be available for its role in transcriptional control.
