Nitric oxide (NO) acts as intracellular second messenger by stimulating
Guanylyl cyclase
Nitric Oxide as a Second Messenger
Nitric oxide (NO) is a fascinating molecule in the body. It's not just a simple gas; it acts as an important signaling molecule. Unlike many other messengers that bind to receptors on the cell surface, NO can often pass through cell membranes because it's a small, lipid-soluble molecule. Once inside the cell, it works as an intracellular second messenger, triggering specific responses.
NO Action: Stimulating Guanylyl Cyclase
One of the primary ways Nitric oxide (NO) functions as an intracellular second messenger is by interacting with and stimulating a particular enzyme. This enzyme is called Guanylyl cyclase. There are different forms of this enzyme, including soluble guanylyl cyclase (sGC), which is a major target for NO.
When NO stimulates Guanylyl cyclase, the enzyme becomes active. Its main job is to convert a molecule called guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP). This cGMP molecule then acts as another second messenger within the cell, mediating various effects like relaxing smooth muscle (leading to vasodilation), affecting nerve cells, and influencing immune responses.
Therefore, Nitric oxide (NO) exerts many of its biological effects by stimulating Guanylyl cyclase, leading to increased levels of cGMP inside the cell.
Analyzing Other Options
Let's briefly look at why the other options are not the correct answer:
- Phosphodiesterase: These enzymes break down cyclic nucleotides like cGMP and cAMP, effectively terminating their signaling role. NO doesn't stimulate phosphodiesterase; it works upstream by increasing cGMP production.
- Nitric oxide synthase: This is the enzyme that *produces* Nitric oxide (NO) from the amino acid arginine. While essential for the availability of NO, it is not the enzyme that NO itself stimulates as a second messenger.
- Adenylyl cyclase: This enzyme converts ATP into cyclic adenosine monophosphate (cAMP), which is another important second messenger. Adenylyl cyclase is often regulated by G protein-coupled receptors, but it is not directly stimulated by Nitric oxide (NO).
Based on the mechanism of NO signaling, it directly stimulates Guanylyl cyclase.
Important Questions from Cell signaling
In the table below Column A lists ligands and Column B lists classes of receptors
Column A Column B A Serotonin i Binding activates a G-protein which activates or inhibits an enzyme that generates a specific second messenger and opens ion channel B Interferons ii Binding causes receptor monomers to dimerize. Dimeric receptor then interacts with and activates one or more cytosolic tyrosine protein kinases C Glycine iii Binding changes the conformation of the receptor so that specific ions flow through it D Insulin iv Binding leads to activation of intrinsic tyrosine kinase activity Which one is the correct match?
Receptor for which one of the following proteins spans the plasma membrane of target cells but DOES NOT contain intrinsic protein kinase activity?
Which one of the following amino acids is characteristic of and is conserved in response regulator of plant two-component systems?
Which one of the following signaling molecules is NOT a protein or a peptide?
Receptor tyrosine kinases (RTKs) form a large and important class of cell surface receptors whose ligands are soluble or membrane bound protein or peptide hormones. Which of the following statement is INCORRECT?
