Nitric oxide synthase is a cytochrome P-450 type hemoprotein.
Nitric oxide synthase is a cytochrome P-450 type hemoprotein.
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DOI：
10.1021/bi00144a001
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发表时间：
1992-07
期刊：
影响因子：
2.9
通讯作者：
K. White;M. Marletta
中科院分区：
文献类型：
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作者：
K. White;M. Marletta
一氧化氮已成为一种重要的哺乳动物代谢中间产物，参与重要的生理功能，如血管舒张，神经元传递和细胞停滞。一氧化氮合酶（NOS）催化L-精氨酸的五电子氧化为瓜氨酸和一氧化氮。反应的共底物包括分子氧和NADPH。此外，还需要四氢生物蝶呤。NOS还含有辅酶FAD和FMN，并显示出与NADPH-细胞色素P-450还原酶显著的氨基酸序列同源性。在这里，我们报告的诱导型巨噬细胞NOS作为细胞色素P-450型血红素蛋白的鉴定。吡啶血色素测定表明，NOS含有结合原卟啉IX血红素。还原的一氧化碳结合光谱显示在447 nm处的最大吸收，指示细胞色素P-450血红素蛋白。一氧化碳和氧气的混合物（80%/20%）有效地抑制了反应（73 - 79%），表明血红素直接在L-精氨酸氧化转化为一氧化氮和瓜氨酸中起作用。此外，从大鼠小脑部分纯化的NOS被CO抑制，这表明这种亚型也可能含有P-450型血红素。NOS是真核生物中可溶性细胞色素P-450的第一个例子。此外，FAD和FMN的存在表明这是第一种催化自给自足的哺乳动物P-450酶，在同一多肽上含有还原酶和血红素结构域。
Nitric oxide has emerged as an important mammalian metabolic intermediate involved in critical physiological functions such as vasodilation, neuronal transmission, and cytostasis. Nitric oxide synthase (NOS) catalyzes the five-electron oxidation of L-arginine to citrulline and nitric oxide. Cosubstrates for the reaction include molecular oxygen and NADPH. In addition, there is a requirement for tetrahydrobiopterin. NOS also contains the coenzymes FAD and FMN and demonstrates significant amino acid sequence homology to NADPH-cytochrome P-450 reductase. Herein we report the identification of the inducible macrophage NOS as a cytochrome P-450 type hemoprotein. The pyridine hemochrome assay showed that the NOS contained a bound protoporphyrin IX heme. The reduced carbon monoxide binding spectrum shows an absorption maximum at 447 nm indicative of a cytochrome P-450 hemoprotein. A mixture of carbon monoxide and oxygen (80%/20%) potently inhibited the reaction (73-79%), showing that the heme functions directly in the oxidative conversion of L-arginine to nitric oxide and citrulline. Additionally, partially purified NOS from rat cerebellum was inhibited by CO, suggesting that this isoform may also contain a P-450-type heme. NOS is the first example of a soluble cytochrome P-450 in eukaryotes. In addition, the presence of FAD and FMN indicates that this is the first catalytically self-sufficient mammalian P-450 enzyme, containing both a reductase and a heme domain on the same polypeptide.