On the Formation of Bile Pigments from Heme Proteins
Hamilton, A.D. and David Dolphin
It is proposed that the catabolism of heme to biliverdin involves an initial epoxidation of a protein-bound porphyrin at the exposed methine bridge. Rearrangement of the γ- to an α-epoxide followed by ring opening to a homooxaporphyrin would generate an electron-rich system capable of reacting with molecular oxygen to form a dioxetane. Fragmentation of the dioxetane to a mono formate ester of biliverdin followed by loss of CO would give the bile pigment.