Nitric Oxide Synthase: Difference between revisions
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[[Image:NOS_OVERSIGT.JPG|800 px|right]] | [[Image:NOS_OVERSIGT.JPG|800 px|right]] | ||
The NOS homodimer is composed of two subunits, each containing two domains: an oxygenase domain and a reductase domain. The subunits are held together by a Zinc ion, which is bound by 4 cystein amino acid present in the oxygenase domain, two in each domain. Further, many amino acid interactions also hold the sunbunits together. Binding of the two types of domains is caused by CaM. The reductase domain supplies electrons for the NOS reaction which takes place in the oxygenase domain. The reductase domain contains two redox-active prosthetic groups, FAD and FMN. NADPH binds to the domain and passes on an electron to FAD which passes the electron on to FMN. FMN passes the electron on to the Heme in the oxygenase domain of the opposite subunit. The oxygenase domain contains H<sub>4</sub>B (5,6,7,8-tetrahydrobiopterin)and the already mentioned Heme ion (Fe(III)). These two are also redox active groups. H<sub>4</sub>B is required by NOS in order to produce NO and not H<sub>2</sub>O<sub>2</sub>. Besides Heme and H<sub>4</sub>B, the oxygenase domain binds the substrate L-arginine which takes part in the NO synthase reaction (see below). | The NOS homodimer is composed of two subunits, each containing two domains: an oxygenase domain and a reductase domain. The subunits are held together by a Zinc ion, which is bound by 4 cystein amino acid present in the oxygenase domain, two in each domain. Further, many amino acid interactions also hold the sunbunits together. Binding of the two types of domains is caused by CaM. The reductase domain supplies electrons for the NOS reaction which takes place in the oxygenase domain. The reductase domain contains two redox-active prosthetic groups, FAD and FMN. NADPH binds to the domain and passes on an electron to FAD which passes the electron on to FMN. FMN passes the electron on to the Heme in the oxygenase domain of the opposite subunit. The oxygenase domain contains H<sub>4</sub>B (5,6,7,8-tetrahydrobiopterin)and the already mentioned Heme ion (Fe(III)). These two are also redox active groups. H<sub>4</sub>B is required by NOS in order to produce NO and not H<sub>2</sub>O<sub>2</sub>. Besides Heme and H<sub>4</sub>B, the oxygenase domain binds the substrate L-arginine which takes part in the NO synthase reaction (see below). | ||
