Kikuchi G, Yoshida T
Ann Clin Res. 1976;8 Suppl 17:10-7.
The heme oxygenase system was reconstituted from heme oxygenase purified from pig spleen microsomes and NADPH-cytochrome c reductase purified from pig liver microsomes. The pig spleen heme oxygenase does not appear to involve cytochrome P-450 but seems to be a protein which readily binds heme to form a heme-protein complex which behaves as an active enzyme and consequently the heme on the enzyme protein is decomposed by its own oxidative activity. The sequence of heme decomposition by the reconstituted heme oxygenase system is quite similar to that in the non-enzymic coupled oxidation of myoglobin and ascorbic acid. In the reconstituted complete reaction system the stoichiometric ratio of decrease of heme, yield of biliverdin, oxidation of NADPH, and consumption of O2 was approximately 1:1:7--8:5--6 when the blank values were subtracted. In the reaction with the pig spleen microsomal preparation the stoichiometric ratio of the decrease of heme, yield of bilirubin, oxidation of NADPH, and consumption of O2 was approximately 1:0.8:9--10:6--7. Larger consumptions of NADPH AND O2 than expected may be due to side reactions. Hemopexin-heme complex was a poor substrate for heme oxygenase. Superoxide dismutase exerted no effect on either the rate or the stoichiometry of the heme oxygenase reaction. Catalase did not affect the rates of heme decomposition and NADPH oxidation, but reduced the rate of O2 consumption by about 30%.
血红素加氧酶系统是由从猪脾微粒体中纯化得到的血红素加氧酶和从猪肝微粒体中纯化得到的NADPH - 细胞色素c还原酶重构而成。猪脾血红素加氧酶似乎不涉及细胞色素P - 450，而是一种能轻易结合血红素形成血红素 - 蛋白质复合物的蛋白质，该复合物具有活性酶的特性，因此酶蛋白上的血红素会通过自身的氧化活性分解。重构的血红素加氧酶系统分解血红素的过程与肌红蛋白和抗坏血酸的非酶偶联氧化过程非常相似。在重构的完整反应体系中，扣除空白值后，血红素减少、胆绿素生成、NADPH氧化和氧气消耗的化学计量比约为1:1:7 - 8:5 - 6。在与猪脾微粒体制剂的反应中，血红素减少、胆红素生成、NADPH氧化和氧气消耗的化学计量比约为1:0.8:9 - 10:6 - 7。NADPH和氧气的消耗比预期的多，可能是由于副反应。血色素 - 血红素复合物是血红素加氧酶的不良底物。超氧化物歧化酶对血红素加氧酶反应的速率和化学计量比均无影响。过氧化氢酶不影响血红素分解和NADPH氧化的速率，但使氧气消耗速率降低了约30%。
