Destruction of cytochrome P-450 by ethylene. Structure of the resulting prosthetic heme adduct.

The prosthetic heme of cytochrome P-450 is converted during the metabolism of ethylene into an abnormal hepatic porphyrin. This porphyrin has been isolated, purified, and characterized by field desorption mass spectrometry and 360-MHz nuclear magnetic resonance spectroscopy. It has been unambiguously identified as one of the four possible isomers of N-(2-hydroxyethyl)protoporphyrin IX (isolated as the dimethyl ester). The isomer which is obtained bears the N-alkyl group on one of the two propionic acid-substituted pyrrole rings in the porphyrin. Strong support is provided by the structure of this porphyrin for our contention that the prosthetic heme of cytochrome P-450 is alkylated during attempted transfer of the catalytically-activated oxygen to the pi-bond of destructive unsaturated substrates.