Studies on ferrochelatase. 1. Assay and properties of ferrochelatase from a pig-liver mitochondrial extract

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Abstract
A rapid and versatile assay for ferrochelatase has been described which involves the measurement of pyridine haemochromogen spectra. A ferrochelatase extract from pig liver was most active when incubated in vacuo activity was completely inhibited by aerobic conditions. Ferrochelatase inserted Fe2+ ions, but not Fe3+ ions, into mesoporphyrin. GSH stimulated activity only when iron was added in the ferric form. Meso- and proto-porphyrins were substrates for ferrochelatase but the corresponding porphyrinogens did not appear to be used. No accumulation of reduced prophyrin intermediates could be detected. The pig-liver extract will not catalyse the exchange of Fe2+ ions with haemoglobin but the reversibility of haem formation from protoporphyrin has been demonstrated.