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Show STUDIES OF HEME A BIOSYNTHESIS Cytochrome c oxidase (CcO) is the terminal enzyme in the electron transport chain in all plants, animals, aerobic yeast, and many bacteria. This enzyme contains a heme A cofactor at the active site that binds molecular oxygen for reduction to water. Our research focuses on the biosynthesis of heme A and its insertion into CcO. Heme A is produced from heme B via two enzymes, heme O synthase (HOS) and heme A synthase (HAS). HOS converts the C2 ethyl group into a 17-hydroxy-ethyl farnesyl moiety, and HAS oxidizes the C8 methyl group to an aldehyde. It has been shown that HAS is a novel histidine lig-ated heme monooxygenase. Conserved residues have been mutated to assess their mechanistic importance. In vivo assays are currently underway to assess the activity of these mutants. Since free heme is cyto-toxic, studies are underway to understand how heme is transferred through this biosynthetic pathway. Evidence will be presented that HOS and HAS interact to effect this transformation. George W. Chaus Sophomore Biology maveric87@hotmail.com Stephen J. Brown Sophomore Biology Faculty Sponsor: Eric L. Hegg Dept. of Chemistry Hegg@chemistry.utah.edu 19 |