Trafficking of Heme and Porphyrins in Metazoa

The mechanisms of heme trafficking and transport with specific emphasis on metazoans has been reported. Heme is the prosthetic group of proteins that perform diverse functions such as oxygen transport (globins), xenobiotic detoxification (cytochrome P450s), oxidative metabolism (cytochrome c oxidase), gas sensing (soluble guanylate cyclases) and input/regulation of the circadian clock. The subsequent side chain modification is catalyzed by coproporphyrinogen oxidase (CPOX), which is located on the mitochondrial outer membrane (OM) facing the inter-membrane space (IMS). There are 29 outer membrane heme receptors that have been identified from different species of Gram-negative bacteria. Several Gram-negative bacteria have ABC transporters that secrete small extracellular proteins called hemophores.