血红蛋白催化的视黄酸5,6 -环氧化反应。
Haemoglobin-catalysed retinoic acid 5,6-epoxidation.
作者信息
Iwahashi H, Ikeda A, Kido R
出版信息
Biochem J. 1985 Dec 1;232(2):459-66. doi: 10.1042/bj2320459.
Examination of the subcellular distribution of retinoic acid 5,6-epoxidase activity in rat liver and human liver homogenates showed that there is a prominent peak of activity in a high-density fraction. A corresponding peak was also detected in rat blood and human blood. Retinoic acid 5,6-epoxidation was catalysed by human blood cells but not by human plasma, and purified human haemoglobin also catalysed the epoxidation of retinoic acid to 5,6-epoxyretinoic acid. These results suggest that retinoic acid 5,6-epoxidase activity in human liver and rat liver homogenates is partially due to the presence of residual blood cells, and particularly haemoglobin, in the homogenates. In the retinoic acid 5,6-epoxidation catalysed by human haemoglobin, molecular O2 was required and its reaction was stimulated by Triton X-100. Boiling of haemoglobin solution resulted in an 94% decrease in the activity. NADPH (1 mM) and NADH (1 mM) completely [2-mercaptoethanol (5 mM) almost completely] inhibited the 5,6-epoxidation catalysed by haemoglobin, but catalase, superoxide dismutase and mannitol showed no inhibitory effect. CN- ion (100 mM) inhibited the reaction, but N3- ion (100 mM) did not.
对大鼠肝脏和人肝脏匀浆中视黄酸5,6 - 环氧化酶活性的亚细胞分布进行检测，结果表明在高密度组分中有一个明显的活性峰。在大鼠血液和人血液中也检测到了相应的峰。视黄酸5,6 - 环氧化反应由人血细胞催化，而人血浆则无此催化作用，纯化的人血红蛋白也能催化视黄酸环氧化生成5,6 - 环氧视黄酸。这些结果表明，人肝脏和大鼠肝脏匀浆中的视黄酸5,6 - 环氧化酶活性部分归因于匀浆中存在残留血细胞，尤其是血红蛋白。在人血红蛋白催化的视黄酸5,6 - 环氧化反应中，需要分子氧，其反应受Triton X - 100刺激。血红蛋白溶液煮沸后活性降低94%。NADPH（1 mM）和NADH（1 mM）完全[2 - 巯基乙醇（5 mM）几乎完全]抑制血红蛋白催化的5,6 - 环氧化反应，但过氧化氢酶、超氧化物歧化酶和甘露醇无抑制作用。CN⁻离子（100 mM）抑制反应，但N₃⁻离子（100 mM）无此作用。
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