The Escherichia coli visA gene encodes ferrochelatase, the final enzyme of the heme biosynthetic pathway.

An Escherichia coli mutant with a disrupted visA gene was defective in ferrochelatase activity but expressed wild-type levels of protoporphyrinogen oxidase activity. The visA coding region was placed under the transcriptional control of T7 RNA polymerase in an E. coli expression system, and the product was expressed as a 38-kDa protein. The overexpressed protein was purified to near homogeneity and was found to contain ferrochelatase activity. The data show that the visA gene encodes ferrochelatase, and we propose that it be renamed hemH to reflect that conclusion.