bps 401 final nitric oxide

List the nitric oxide synthases (NOS)

NOS-1 (neuronal, nNOS)

NOS-2 (inducible, iNOS)

NOS-3 (endothelial, eNOS)

What are the characteristics of NOS-1? (nNOS)

• Present in central and peripheral neuronal cells

• Present in skeletal muscle

• Dependent on Ca2+

• Used for neuronal communication

What are the characteristics of NOS-2? (iNOS)

• Present in smooth muscle cells

• Present in macrophages

• Independent of intracellular Ca2+; constitutively active

• Inducible in presence of inflammatory cytokines

What are the characteristics of NOS-3? (eNOS)

• Present in vascular endothelial cells

• Ca2+ dependent

• Responsible for vascular regulation

How is NOS activated?

Glutamate NT binds to NDMA receptor

Calcium channels open, causing influx to cell → bind calmodulin → actives NOS → NO synthesis

What are the NO signaling mechanisms?

1. Metalloproteins

2. Thiols

3. Tyrosine nitration

Describe NO signaling, metalloproteins

Describe NO signaling, thiols

NO interacts with metals (especially iron in heme)

Describe NO signaling, tyrosine nitration

NO undergoes oxidative and reductive reactions

• Variety of nitrogen oxides that nitrosylate thiols and add nitrate to tyrosines or are stable oxidation products

Describe the ways nitric oxide can be inactivated

NO reaction with heme and hemoproteins → leads s-nitrosylation of hemoglobin → transport NO throughout the vasculature

NO is inactivated by reacting with O2 → nitrogen dioxide

NO reacts with superoxide → peroxynitrite