Nitric oxide synthase prosthetic groups

Prosthetic groups contained within NOS. Nitric oxide synthases are isolated containing approximately one molecule each of heme, FAD, and FMN per subunit, and also contain variable quantities of tetrahydrobiopterin (0.1 to 1 molecule per subunit). 

Baek, K. J., Thiel, B. A., Lucas, S., and Stuehr, D, J, (1993). Macrophage nitric oxide synthase subunits. Purification, characterization, and role of prosthetic groups and sub-... 

Griscavage, J. M., Fukuto, J. M., Komori, Y., and Ignarro, L. J. (1994). Nitric oxide inhibits neuronal nitric oxide synthase by interacting with the heme prosthetic group. Role of tetrahydrobiopterin in modulating the inhibitory action of nitric oxide. /. Biol. Chem. 269, 21644-21649. 

Recent discovery of nitric oxide ( NO), which controls and influences a number of critical physiological processes, as a mammalian metabolic intermediate has stimulated rapid progress of studies on nitric oxide synthase (NOS) [267-269]. The formation of NO from L-arginine in mammalian cells is catalyzed by NOS. The inducible NOS has now been known to contain a cytochrome P-450 type iron-protoporphyrin IX prosthetic group and 1 equiv each of FAD and FMN per subunit [270, 271]. Further, NOS requires NADPH to proceed the reactions. Interestingly, P-450 itself has been demonstrated to catalyze NO synthesis [272, 273]. While the detail of the reaction mechanism is still obscure. Scheme 17 summarizes proposed reaction sequences [269]. 

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