Cyclic adenosine monophosphate second messenger function

The most common second messenger activated by protein/peptide hormones and catecholamines is cyclic adenosine monophosphate (cAMP). The pathway by which cAMP is formed and alters cellular function is illustrated in Figure 10.1. The process begins when the hormone binds to its receptor. These receptors are quite large and span the plasma membrane. On the cytoplasmic surface of the membrane, the receptor is associated with a G protein that serves as the transducer molecule. In other words, the G protein acts as an intermediary between the receptor and the second messengers that will alter cellular activity. These proteins are referred to as G proteins because they bind with guanosine nucleotides. In an unstimulated cell, the inactive G protein binds guanosine diphosphate (GDP). When the hormone... 

TTie second messenger, for example cyclic adenosine monophosphate (cAMP), then activates cAMP-dependent protein kinase which modulates the function of a broad range of membrane receptors, intracellular enzymes, ion channels and transcription factors. 

Adenylyl cyclase is the effector enzyme that synthesizes cyclic adenosine monophosphate (cAMP) from ATP. Cyclic AMP functions as a second messenger to relay extracellular signals to intracellular enzymes such as protein kinase A. Adenylyl cyclases are integral membrane proteins that... 

Cyclic nucleotides, 3, 5 -cyclic adenosine monophosphate (cAMP) and 3, 5 -cyclic guanosine monophosphate (cGMP), function to regulate cell-to-cell communication processes (33). Cellular communication follows primarily three pathways. The first involves the transmission of electrical impulses via the nervous system. The second involves chemical messengers or hormonal secretions. The third involves de novo protein synthesis. All three processes are usually in response to some demand or stimulus and involve, at least to some extent, regulation by cyclic nucleotides ... 

It has been suggested139 that adenosine 3 5 -monophosphate (cyclic AMP) functions as an intracellular second messenger which mediates the effects of specific hormones on their target cells. According to this concept, a hormone such as... 

Cyclic 3, 5 -adenosine monophosphate (c-AMP) is known to be of key significance as a regulator of cellular metabolism. In mammals it functions as a second messenger for a number of hormones. Abnormalities in c-AMP formation, or in its action, seem to be involved in the pathology of various hormonal and nonendocrine diseases. 

Another important nucleotide is adenosine 3, 5 -monophosphate, commonly known as cyclic AMP. Cyclic AMP is called a second messenger because it serves as a link between several hormones (the first messengers) and certain enzymes that regulate cellular function. Secretion of certain hormones, such as adrenaline, activates adenylate cyclase, the enzyme responsible for the synthesis of cyclic AMP from ATP. Cyclic AMP then activates an enzyme, generally by phosphorylating it. Cyclic nucleotides are so important in regulating cellular reactions that an entire scientific journal is devoted to these processes. 

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