SPECIFICITY OF HEME OXYGENASE - A STUDY WITH SYNTHETIC HEMINS
SPECIFICITY OF HEME OXYGENASE - A STUDY WITH SYNTHETIC HEMINS
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DOI：
10.1021/bi00521a012
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发表时间：
1981-01-01
期刊：
影响因子：
2.9
通讯作者：
FRYDMAN, B
中科院分区：
文献类型：
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作者：
FRYDMAN, RB;TOMARO, ML;FRYDMAN, B
从大鼠肝脏中提取的一种微粒体血红素加氧酶制剂对大量合成的铁卟啉进行了酶促氧化。它们在C6和C7上都有两个共同的邻丙酸残基。I型铁卟啉不是该酶的底物。在C2和C4上携带吸电子取代基(酰基残基)的铁卟啉是血红素加氧酶的底物，尽管产物产率降低。几种铁卟啉，如氯化血红素XIII和氯化血红素III，是比天然底物氯化血红素IX更好的血红素加氧酶底物。α-亚甲基桥的酶催化氧化是选择性的，得到的α-胆绿素被胆绿素还原酶还原为相应的α-胆红素。在没有NADPH的情况下，用氯化高铁血红素IX和氯化高铁血红素XIII预先孵育酶体系，可抑制它们的氧化。无铁的卟啉在C6和C7上携带2个邻近的丙酸残基，与后者预先孵育时是酶系统的抑制剂。血凝素IX的存在抑制了氯化血红素IX的酶促氧化。
A large number of synthetic iron porphyrins were enzymatically oxidized by a microsomal heme oxygenase preparation from rat liver. They all had in common 2 vicinal propionic acid residues at C6 and C7. Iron porphyrins of type I were not substrates of the enzyme. Iron porphyrins that carried electron-withdrawing substituents (acyl residues) at C2 and C4 were substrates of heme oxygenase, although the product yields were reduced. Several iron porphyrins, such as hemin XIII and hemin III, were better substrates of heme oxygenase than the natural substrate hemin IX. Enzymatic oxidation was selective for the .alpha.-methine bridge, and the .alpha.-biliverdins obtained were reduced by Biliverdin reductase to the corresponding .alpha.-bilirubins. Preincubations of the enzymatic system with hemin IX and hemin XIII in the absence of NADPH resulted in an inhibition of their oxidation. The iron-free porphyrins which carried 2 vicinal propionic acid residues at C6 and C7 were inhibitors of the enzymatic system when preincubated with the latter. The presence of hematochemin IX suppressed the enzymatic oxidation of hemin IX.