Résumé
A cyclic nucleotide (cNMP) is a single-phosphate nucleotide with a cyclic bond arrangement between the sugar and phosphate groups. Like other nucleotides, cyclic nucleotides are composed of three functional groups: a sugar, a nitrogenous base, and a single phosphate group. As can be seen in the cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) images, the 'cyclic' portion consists of two bonds between the phosphate group and the 3' and 5' hydroxyl groups of the sugar, very often a ribose. Their biological significance includes a broad range of protein-ligand interactions. They have been identified as secondary messengers in both hormone and ion-channel signalling in eukaryotic cells, as well as allosteric effector compounds of DNA binding proteins in prokaryotic cells. cAMP and cGMP are currently the most well documented cyclic nucleotides, however there is evidence that cCMP (with cytosine) is also involved in eukaryotic cellular messaging. The role of cyclic uridine monophosphate (cUMP) is even less well known. Discovery of cyclic nucleotides has contributed greatly to the understanding of kinase and phosphatase mechanisms, as well as protein regulation in general. Although more than 50 years have passed since their initial discovery, interest in cyclic nucleotides and their biochemical and physiological significance continues. The understanding of the concept of second messengers, and in particular the role of cyclic nucleotides and their ability to relay physiological signals to a cell, has its origins in the research of glycogen metabolism by Carl and Gerty Cori, for which they were awarded a Nobel Prize in Physiology or Medicine in 1947. A number of incremental but important discoveries through the 1950s added to their research, primarily focusing on the activity of glycogen phosphorylase in dog liver. Glycogen phosphorylase catalyzes the first step in glycogenolysis, the process of breaking glycogen into its substituent glucose parts.
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Concepts associés (2)
Ribose
Le ribose est un aldopentose (un pentose du type aldose), c'est un ose constitué d’une chaîne de cinq éléments carbone ainsi que d’une fonction aldéhyde. C'est un pentose qui joue un rôle important pour les êtres vivants surtout dans sa forme D. Son rôle biologique a été découvert par Phoebus Levene et en 1908 aux États-Unis, au Rockefeller Institute for Medical Research à New York et l'on a pu croire que ribose, était "rib"-ose, supposé de Rockefeller Institute of Biochemistry.
Signalisation cellulaire
La signalisation cellulaire est un système complexe de communication qui régit les processus fondamentaux des cellules et coordonne leur activité. La capacité des cellules à percevoir leur micro-environnement et à y répondre correctement est à la base de leur développement et de celui des organismes multicellulaires, de la cicatrisation et du système immunitaire, ainsi que de l'homéostasie tissulaire normale. Des dysfonctionnements dans le traitement de l'information cellulaire peuvent être responsables de maladies telles que le cancer, les maladies auto-immunes et le diabète.