<prompt> Heme is which porphyrin?Type IType IIType IIIType IV  <response>: The protoporphyrinogen-III is oxidized by the enzyme protoporphyrinogen oxidase to protoporphyrin-III in the mitochondria. The xidation requires oxygen.The methylene bridges -CH2 are oxidized to methenyl bridges -CH and colored porphyrins are formed.Protoporphyrins -9 is thus formed. The last step in the formation of heme is the attachment of ferrous iron to the protoporphyrin. The enzyme is heme synthase or ferrochelatase, which is also located in the mitochondria. REFERENCE : DM VASUDEVAN TEXTBOOK SEVENTH EDITION ; PAGE NO : 273. 