Heme A biosynthesis

Respiration in plants, most animals and many aerobic microbes is dependent on heme A. This is a highly specialized type of heme found as prosthetic group in cytochrome a-containing respiratory oxidases. Heme A differs structurally from heme B (protoheme IX) by the presence of a hydroxyethylfarnesyl group instead of a vinyl side group at the C2 position and a formyl group instead of a methyl side group at position C8 of the porphyrin macrocycle. Heme A synthase catalyzes the formation of the formyl side group and is a poorly understood heme-containing membrane bound atypical monooxygenase. This review presents our current understanding of heme A synthesis at the molecular level in mitochondria and aerobic bacteria. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (171 K)Download as PowerPoint slideHighlights► Heme A is a specialised type of heme found in respiratory cytochrome oxidases. ► Heme A and chlorophyll b biosynthesis have common features. ► Heme A synthase is a membrane bound heme-containing atypical monooxygenase ► Heme A synthase has evolved from a variant with 4 transmembrane segments.