1.3.98.5 metabolism the enzyme, along with the terminal two pathway enzymes protoporphyrinogen oxidase HemY and ferrochelatase is required to synthesize heme in vivo and in vitro 751026 1.3.98.5 physiological function Actinobacteria and Firmicutes (high-GC and low-GC Gram-positive bacteria) are unable to synthesize protoporphyrin. Instead, they oxidize coproporphyrinogen to coproporphyrin, insert ferrous iron to make Fe-coproporphyrin (coproheme), and then decarboxylate coproheme to generate protoheme. This pathway is specified by three genes named hemY, hemH, and hemQ and is the most ancient heme synthesis pathway in the Eubacteria 755245 1.3.98.5 physiological function enzymes HemY, HemH and HemQ act as a coproporphyrinogen III oxidase, coproporphyrin III ferrochelatase and Fe-coproporphyrin III oxidase/dehydrogenase 754774 1.3.98.5 physiological function HemQ can stimulate the generation of protoporphyrin IX but not coproporphyrin III 752717 1.3.98.5 physiological function the presence of HemQ along with the terminal two pathway enzymes, protoporphyrinogen oxidase (HemY) and ferrochelatase, is required to synthesize heme in vivo and in vitro. To be fully functional in vitro, HemQ requires the presence of a bound heme 751026