Probable inactive heme oxygenase. Binds protoporphyrin IX, a precursor for both heme and chlorophyll biosynthesis. Plays a minor role in phytochrome assembly and photomorphogenesis. A number of isoforms are produced. According to EST sequences. Widely expressed at low levels. Slight reduction in plant size and chlorophyll content, and early flowering. Belongs to the heme oxygenase family. Lacks the conserved His residue involved in heme iron binding and essential for heme oxygenase activity. Its enzyme activity is therefore unsure.