Nitric Oxide Synthase: Physiology, Biochemistry, and Mechanism

The video explores nitric oxide synthase, an enzyme related to cytochrome P-450, detailing its structure, function, and mechanism. It highlights the role of tetrahydrobiopterin in stabilizing the enzyme and quenching free radicals. The video explains the electron flow within the enzyme, its self-sufficiency, and the different types of nitric oxide synthase, including inducible, neuronal, and endothelial forms. The mechanism of nitric oxide production from L-arginine is discussed, along with the enzyme's role in various physiological processes.

What is the primary function of nitric oxide synthase?

• To convert glucose to energy

• To break down fatty acids

• To synthesize proteins

• To produce nitric oxide from L-arginine

How does tetrahydrobiopterin affect nitric oxide synthase?

• It acts as a substrate for the enzyme

• It stabilizes the enzyme and affects reactivity

• It directly participates in oxygen activation

• It inhibits the enzyme's activity

What is the significance of the heme group in nitric oxide synthase?

• It stores energy

• It activates molecular oxygen

• It transports electrons

• It binds to carbon dioxide

What distinguishes nitric oxide synthase from cytochrome P-450 in terms of electron transfer?

• It requires an external electron source

• It uses ATP instead of NADPH

• It has a built-in reductase domain

• It does not involve electron transfer

Which type of nitric oxide synthase is involved in immune response?

• Mitochondrial nitric oxide synthase

• Neuronal nitric oxide synthase

• Endothelial nitric oxide synthase

• Inducible nitric oxide synthase

What role does nitric oxide play in blood vessels?

• It causes blood vessels to rupture

• It constricts blood vessels

• It dilates blood vessels

• It has no effect on blood vessels

What is the role of guanylate cyclase in nitric oxide signaling?

• It inhibits nitric oxide production

• It converts GTP to cyclic GMP

• It synthesizes nitric oxide

• It breaks down nitric oxide

How does nitric oxide affect smooth muscle cells?

• It causes relaxation

• It causes contraction

• It has no effect

• It causes cell death

What is the main product of the reaction catalyzed by nitric oxide synthase?

• L-citrulline

• L-tyrosine

• L-lysine

• L-glutamine

What is a potential issue with nitric oxide as a free radical?

• It can form stable compounds

• It can react with superoxide to form peroxynitrite

• It is completely harmless

• It does not interact with other molecules