The phosphorylation is the addition of a group Phosphate (PO₄) with a Protéine or a small molecule, the such Glucose or the Adénine. Its prominent role in Biochimie is the subject of very many research (the database MEDLINE announces more: 100000 articles on this subject, for the majority concerning phosphorylation of the proteins ).

Phosphorylation of proteins

Function

At the Eucaryotes, the phosphorylation of proteins is one of the mechanisms of regulation most important and most frequent. Many a Enzyme S and receiving S is put in position " actif" or " non-actif" by a phosphorylation or a dephosphorylation. The phosphorylation is catalyzed by various proteins specific kinases , whereas the Phosphatase S take care of die phosphoryler. Kinases and phosphatases are in general controlled by external signals, like the Hormone S, Cytokine S and others growth factors like by the variations of intracellular Calcium. An example can be used as illustration of antagonism between phosphatases and kinases is that given by balance between the degradation of the Glycogène (Glycogénolyse) and its synthesis (Glycogénogénèse). This balance is controlled by phosphorylation/dephosphorylation of the enzymes glycogen phosphorylase, which degrades glycogen and, glycogen synthase which increases the size of glycogen by grafting molecules of glucose there. The phosphorylation state as of these two enzymes is controlled by the hormones Glucagon, Adrénaline and Insuline.

Networks of indication

See also: Transduction of signals

Types of phosphorylation

See also: Protein kinase

The phosphorylations take place on the side chains of the amino-acids comprising a function alcohol: Serine and Thréonine. Another kinase phosphoryl class the proteins on the level of the Tyrosin S. Enfin, of phosphorylations on the level of the Histidine S and Aspartate S are met in the organizations Procaryote S.

Other kinds

ATP, the intermediary " rich person in énergie" cells, is synthesized in the Mitochondrie S by addition of a third grouping phosphates with ADP during the oxydative Phosphorylation. The ATP is also synthesized on the level of phosphorylation of the substrate during the Glycolyse.

In the photosynthetic cells , the ATP is produced on the level of the Chloroplaste after collecting of solar energy by the Photosystème S.

The phosporylation of the oses prevents their exit of the cell, because the conveyer then does not have any more affinity for them. This phosphorylation is the first stage of the Glycolyse and, in a more general way, their Catabolisme.

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