Title: The enzymatic conversion of heme to bilirubin by microsomal heme oxygenase.
Abstract: In the intact organism heme and hemoglobin are converted nearly quantitatively to bilirubin. 1 2 Although several model systems have been proposed, the exact mechanism and the individual steps of this conversion remain unknown.Lemberg3 suggested a coupled oxidation with ascorbate and molecular oxygen, which in vitro leads to formation of the bile pigment precursors choleglobin and verdohemochrome; on acidification, biliverdin is obtained.This nonenzymatic system is unlikely to reflect the physiologic mechanism of heme degradation because it results in formation of a mixture of biliverdin isomers,4 whereas in