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1 NO的合成和NO合成酶 一氧化氮(NO)是由NO合酶(NOS)催化L-精氨酸产生。NO合成部位极广,几乎遍及所有细胞。NOS为含有黄素腺嘌呤二核苷酸(FAD)和黄素核苷酸(FMN)的黄素蛋白,依赖NADPH,需四氢叶酸作为辅助因子。NOS是NO生物合成的关键因素,目前NOS已分离和纯化出三种类型:一为原生型或结构型(cNOS),活性依赖Ca~(2+)/钙调蛋白(CaM),分别存在于内皮细胞和神经元中,在CNS中弥散分布于各脑区,其中以小脑、海马、嗅球的浓度较高。cNOS在生理状态有活性,可合成NO,参与生理功能的调节。二为诱生型NOS(iNOS),几乎分布于所有细胞中,活性不依赖Ca~(2+)/CaM,正常情况下不出现在细胞内,在内毒素、干扰素、TNF和IL-1β等细胞因子刺激下才被激活,释放大量NO,如巨噬细胞中的iNOS。糖皮质激素、IL-4、血小板源生长
1 NO synthesis and NO synthase Nitric oxide (NO) is produced by L-arginine catalyzed by NO synthase (NOS). NO synthesis of a very wide area, almost all cells. NOS is a flavoprotein containing flavin adenine dinucleotide (FAD) and flavin nucleotide (FMN), which is dependent on NADPH and requires tetrahydrofolic acid as a cofactor. NOS is the key factor of NO biosynthesis. At present, three types of NOS have been isolated and purified: one is native or structural type (cNOS), the activity is dependent on Ca2 + / CaM, Endothelial cells and neurons in the CNS in the diffuse distribution in various brain regions, including the cerebellum, hippocampus, olfactory bulb concentration higher. cNOS is active in the physiological state, can synthesize NO, involved in the regulation of physiological functions. The second is induced NOS (iNOS), distributed in almost all cells, the activity does not depend on Ca ~ (2 +) / CaM, under normal circumstances does not appear in the cells, endotoxin, interferon, TNF and IL- Such as cytokines stimulated only activated, release a large number of NO, such as macrophage iNOS. Glucocorticoids, IL-4, platelet-derived growth