Cyclic adenosine monophosphate is a molecule that, from a biochemical perspective, is derived from adenosine triphosphate. In many cases, cyclic adenosine monophosphate is simply referred to by the abbreviation cAMP. The molecule functions as a so-called second messenger in the signal transduction of cells. In this context, cyclic adenosine monophosphate primarily serves to activate certain types of protein kinases.
What is cyclic adenosine monophosphate?
Basically, cyclic adenosine monophosphate represents a special signaling substance that, from a chemical point of view, belongs to the category of nucleotides. Within the framework of numerous signaling cascades associated with the action of hormones as well as metabolism, the molecule assumes the function of a second messenger. Cyclic adenosine monophosphate has a molar mass of 329.21 grams per mole. Cyclic adenosine monophosphate plays an important role in the regulation of metabolism. Because the molecule activates protein kinases, many metabolic functions are regulated. One example is the degradation of glycogen to glucose. Cyclic adenosine monophosphate also plays an important role with regard to lipolysis as well as the release of tissue hormones, such as somatostatin.
Function, effects, and roles
Cyclic adenosine monophosphate is characterized by a variety of significant functions and effects in the organism. Therefore, the molecule has an important role in a functioning metabolism and general human health. Cyclic adenosine monophosphate is particularly relevant in the activation of protein kinases. The molecule primarily activates type A protein kinases. By causing phosphorylation, these substances exert numerous effects. For example, they lead to phosphorylation of calcium ion channels. As a result, the corresponding channels open. In addition, they also cause phosphorylation of the so-called myosin light chain kinases. As a result, the smooth muscle relaxes. At the same time, the sensitivity of the corresponding muscles to calcium ions is reduced. It should be noted, however, that according to the current state of medical research, it has not been conclusively clarified whether this mechanism of action has any relevance in vivo. Cyclic adenosine monophosphate also leads to phosphorylation of certain transcription factors, for example CREB. This causes genes induced by the cyclic adenosine monophosphate to be transcribed. In addition, cyclic adenosine monophosphate also performs numerous important functions in bacteria, which in turn may be associated with and relevant to the human organism. In bacteria, cyclic adenosine monophosphate functions as a so-called hunger signal or glucose deficiency signal. However, it has a completely different mechanism of action. Here, the substance plays an important role in the repression of glucose as well as the utilization of lactose and the associated regulatory circuit. If glucose is present in the corresponding medium, the genes of the so-called lactose operon are switched off. This effect makes sense because the utilization of lactose in this case is too costly and not necessary. If glucose is present, the cyclic adenosine monophosphate usually has only a low concentration. If, on the other hand, glucose is withdrawn, the concentration increases by activating a bacterial adenylyl cyclase. In this process, a specific transport protein phosphorylates. This binds to another molecule and activates it. Subsequently, the cyclic adenosine monophosphate binds to the so-called catabolite activator protein. This is also called cAMP receptor protein. The protein activates the transcription factor of the corresponding gene. As a result, the ingestion of lactose begins under starvation conditions.
Formation, occurrence, properties, and optimal levels
Cyclic adenosine monophosphate is synthesized and metabolized under specific conditions. The formation of the molecule occurs in numerous human cells of the body after the substance binds to certain signaling molecules or G-protein-coupled receptors. In this process, the alpha subunit of the G protein is activated. As a result, adenylate cyclase forms cyclic adenosine monophosphate from ATP.During this process, pyrophosphate is cleaved off and esterification of the remaining phosphate group with another group of ribose takes place. During degradation, this ester bond is cleaved by the enzyme phosphodiesterase. When a specific receptor is activated by a hormone, such as glucagon, an odorant or neurotransmitter such as norepinephrine, stimulation of a membrane-bound adenylyl cyclase occurs. This is responsible for the conversion of cellular ATP into the cyclic adenosine monophosphate. Forskolin is known to directly stimulate adenylyl cyclase. In the degradation of cyclic adenosine monophosphate to adenosine monophosphate, the enzyme phosphodiesterase plays an important role as a catalyst. In this process, caffeine has an inhibitory effect on the enzyme.
Diseases and disorders
Since cyclic adenosine monophosphate assumes important functions, for example, in the regulation of metabolic processes in the human organism, disorders have a correspondingly serious effect. Especially for hormone metabolism, cyclic adenosine monophosphate is an important molecule with mediating functions. Cyclic adenosine monophosphate primarily contributes to the activation of enzymes inside cells. These enzymes play an important role in the metabolism of proteins, for example. If the synthesis or transfer of cyclic adenosine monophosphate is disturbed, the corresponding metabolic processes no longer run without errors, which, depending on the metabolic process affected, impairs health and requires endocrinological therapy.
