What is the Difference Between cAMP and cGMP

The main difference between cAMP and cGMP is that cAMP takes part in several biochemical processes, including the regulation of glycogen, sugar, and lipid metabolism whereas cGMP serves as a regulator of ion channel conductance, glycogenolysis, and cellular apoptosis. Furthermore, cAMP has a high concentration in most tissues, while cGMP has a lower concentration. 

CAMP and cGMP are two types of cyclic nucleotides. Moreover, they serve as second messengers due to their broad range of protein-ligand interactions.  

Key Areas Covered 

1. What is cAMP
     – Definition, Structure, Function
2. What is cGMP
     – Definition, Structure, Function
3. What are the Similarities Between cAMP and cGMP
     – Outline of Common Features
4. What is the Difference Between cAMP and cGMP
     – Comparison of Key Differences

Key Terms 

cAMP, cGMP, Cyclic Nucleotides, Second Messengers, Signal Transduction

What is cAMP 

cAMP or Cyclic adenosine monophosphate is an intracellular second messenger for numerous extracellular signals, conveying the cAMP-dependent pathway. Generally, cAMP is synthesized from ATP by the action of the enzyme adenylate cyclase. Also, this enzyme anchors different locations on the inner side of the plasma membrane.

Figure 1: cAMP

Furthermore, the main function of cAMP is to transfer the effect of hormones such as glucagon, adrenaline by the activation of protein kinases. Therefore, it regulates biochemical processes such as glycogen, sugar, and lipid metabolism. Here, cAMP activates protein kinase A at a specific location of its regulatory unit, dissociating the regulatory unit from its catalytic subunit. Thus, it enables the catalytic unit to phosphorylate the substrate proteins, which can be either ion channels or activated or inhibited enzymes.  

What is cGMP 

cGMP or Cyclic guanosine monophosphate is another cyclic nucleotide, which acts as a second messenger as cyclic AMP. Generally, it is synthesized from GTP by the action of the enzyme guanylate cyclase. Moreover, the concentration of cGMP is 10-100 fold lower than the concentration of cAMP in most tissues. However, cGMP serves as a regulator of ion channel conductance, glycogenolysis, and cellular apoptosis.

Figure 2: cGMP

Moreover, cGMP takes part in the relaxation of smooth muscles, basically, in blood vessels. The relaxation leads to vasodilation, increasing the blood flow. On the other hand, it serves as a second messenger in phototransduction in the eye. In the presence of light, the activated phosphodiesterase degrades cGMP. Moreover, the sodium channels in photoreceptors are cGMP-gated. Therefore, these channels are closed in the presence of light due to the lack of cGMP. However, this causes hyperpolarization of the plasma membrane of photoreceptors, transmitting visual information to the brain. 

Similarities Between cAMP and cGMP 

• cAMP and cGMP are two types of cyclic nucleotides. 
• They are single-phosphate nucleotide with a cyclic bond arrangement between the sugar and phosphate groups.   
• Moreover, they have three functional groups: a ribose sugar, a nitrogenous base, and a single phosphate group.   
• They have a broad range of protein-ligand interactions. 
• By that, they activate protein kinases.  
• They serve as second messengers in both hormone and ion-channel signaling in eukaryotes. 
• In addition, they serve as allosteric effector compounds of DNA-binding proteins in prokaryotes. 

Difference Between cAMP and cGMP 

Definition 

cAMP refers to a common second messenger involved in signal transduction cascades while cGMP refers to a cyclic nucleotide, which acts as a second messenger like cAMP. Thus, this explains the main difference between cAMP and cGMP.

Known as  

The cAMP is also known as  3′,5′-cyclic adenosine monophosphate, cyclic adenosine monophosphate, cyclic AMP, etc. while cGMP is also known as 3′,5′-cyclic guanosine monophosphate, cyclic guanosine monophosphate, cyclic GMP, etc. 

Type  

Another difference between cAMP and cGM is that cAMP is a type of adenosine nucleotide while cGMP is a type of guanosine nucleotide. 

Synthesis 

The cAMP is synthesized from ATP by the action of the enzyme adenylate cyclase while is synthesized from GTP by the action of the enzyme guanylate cyclase. 

Concentration 

Moreover, cAMP has a high concentration in many tissues while cGMP has a lower concentration in many tissues. 

Function 

Furthermore, cAMP takes part in the regulation of glycogen, sugar, and lipid metabolism in eukaryotic cells while cGMP takes part regulator of ion channel conductance, glycogenolysis, cellular apoptosis, smooth muscle relaxation, and phototransduction.  

Conclusion 

The cAMP is the cyclic nucleotide, occurring in high concentrations in many tissues. It also serves as a second messenger in the regulation of sugar, glycogen, and lipid metabolism. On the other hand, cGMP is another cyclic nucleotide, occurring in lower concentrations in tissues. However, it takes part in ion channel conductance, glycogenolysis, and cellular apoptosis. Furthermore, it takes part in smooth muscle relaxation and phototransduction. Therefore, the main difference between cAMP and cGMP is their concentration in tissues and function. 

References:

1. Duman RS, Nestler EJ. Functional Roles for cAMP and cGMP. In: Siegel GJ, Agranoff BW, Albers RW, et al., editors. Basic Neurochemistry: Molecular, Cellular, and Medical Aspects. 6th edition. Philadelphia: Lippincott-Raven; 1999. Available Here. 

Image Courtesy:

1. “Cyclic-AMPchemdraw” By Smokefoot – Own work (CC BY-SA 4.0) via Commons Wikimedia   
2. “CGMP2” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia