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Molecules Derived from Amino Acids:- Arginine Is the Precursor for Biological Synthesis of Nitric Oxide

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  862

2026-07-06

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Molecules Derived from Amino Acids:- Arginine Is the Precursor for Biological Synthesis of Nitric Oxide

A surprise finding in the mid-1980s was the role of nitric oxide (NO)—previously known mainly as a compo nent of smog—as an important biological messenger.

This simple gaseous substance diffuses readily through membranes, although its high reactivity limits its range of diffusion to about a 1 mm radius from the site of syn thesis. In humans NO plays a role in a range of physio logical processes, including neurotransmission, blood clotting, and the control of blood pressure. Its mode of action is . Nitric oxide is synthesized from arginine in an NADPH-dependent reaction catalyzed by nitric oxide synthase (Fig. 1), a dimeric enzyme structurally related to NADPH cytochrome P-450 reductase . The reaction is a five-electron oxidation. Each subunit of the enzyme contains one bound molecule of each of four different cofactors: FMN, FAD, tetrahydro biopterin, and Fe3 heme. NO is an unstable molecule and cannot be stored. Its synthesis is stimulated by in teraction of nitric oxide synthase with Ca2-calmodulin .

FIGURE 1 Biosynthesis of nitric oxide. Both steps are catalyzed by nitric oxide synthase. The nitrogen of the NO is derived from the guanidino group of arginine.