Côté J F, Roberge A G
INRS-Santé, Université du Québec, Pointe-Claire, Canada.
Free Radic Biol Med. 1996;21(1):109-15. doi: 10.1016/0891-5849(95)02208-2.
Nitric oxide, derived from L-arginine by the enzyme nitric oxide synthase, is an activator of the soluble guanylate cyclase and a cellular messenger. This work demonstrates that, in cat brain, the neuronal constitutive nitric oxide synthase activity is a) NADPH/calcium dependent, b) independent upon exogenous calmodulin in crude brain supernatant, c) significantly enhanced by exogenous FAD and tetrahydrobiopterin (Vmax: 118 instead of 59.4 pmol of citrulline formed .mg of prot.-1 min-1, d) inhibited by calcium chelators and calmodulin antagonist, and e) present in several neuroanatomical structures. Moreover, the Km value for L-arginine was of 11 microM instead of 41 microM in the presence of FAD and tetrahydrobiopterin in the incubation mixture, thus demonstrating that these cofactors are able to stabilize the enzyme-substrate interactions.
一氧化氮由一氧化氮合酶作用于L-精氨酸产生，是可溶性鸟苷酸环化酶的激活剂和细胞信使。这项研究表明，在猫脑中，神经元组成型一氧化氮合酶活性具有以下特点：a）依赖NADPH/钙；b）在粗脑匀浆上清液中不依赖外源性钙调蛋白；c）外源性黄素腺嘌呤二核苷酸（FAD）和四氢生物蝶呤可显著增强其活性（Vmax：从每分钟每毫克蛋白形成59.4皮摩尔瓜氨酸增至118皮摩尔）；d）受钙螯合剂和钙调蛋白拮抗剂抑制；e）存在于多个神经解剖结构中。此外，在孵育混合物中存在FAD和四氢生物蝶呤的情况下，L-精氨酸的米氏常数（Km）为11微摩尔而非41微摩尔，这表明这些辅因子能够稳定酶与底物的相互作用。
