Furthermore, analogues and derivatives of some prostaglandins have been created that are used in the therapeutic field for the treatment of various conditions (for example, induction of childbirth, treatment of erectile dysfunction, etc.).
polyunsaturated and belonging to the group of eicosanoids (together with lipoxins, thromboxanes and leukotrienes).Prostaglandins are produced by different cells and each of them can produce prostaglandins of different varieties and quantities.
from which the PCs derive, it is possible that there is the presence of additional double bonds. More precisely:
- Prostaglandins having a double bond (present between C-13 and C-14) derive from 8,11,14-eicosatrienoic acid.
- Prostaglandins having two double bonds (one between C-13 and C-14 and one between C-5 and C-6) derive from arachidonic acid (or 5,8,11,14-eicosatetraenoic acid).
- Prostaglandins having three double bonds (one between C-13 and C-14; one between C-5 and C-6 and one between C-17 and C-18) derive from the acid 5,8,11,14,17 -eicosapentaenoic (EPA).
The double bonds present in prostaglandin are indicated with a number next to the letter representing the series; for example: PGE1 indicates an E-series prostaglandin with a double bond; PGE2 indicates an E-series prostaglandin with two double bonds; PGE3 indicates an E-series prostaglandin with three double bonds.
Cis and trans isomerism
We conclude the notes on the nomenclature of prostaglandins by recalling that the presence of a Greek letter next to the number of bonds present in the prostaglandin structure indicates the position of the possible hydroxyl group linked to C-9 (carbon 9) with respect to the possible bonded hydroxyl group at C-11 (carbon 11).
More specifically, the hydroxyl group bound to C-9 can be in position Are you there - in this case it will be indicated with the Greek letter α - or in position trans - in this case it will be indicated with the Greek letter β - with respect to the hydroxyl group linked to C-11.
For example: PGF2α indicates prostaglandin belonging to the F series with two double bonds (therefore deriving from "arachidonic acid) having the hydroxyl group bonded to carbon 9 in position Are you there with respect to the hydroxyl group bonded to carbon 11.
listed in the previous paragraph. As mentioned, depending on the fatty acid from which the synthesis started, the resulting prostaglandins can have one, two or three double bonds within their chemical structure.
In man, the prostaglandins deriving from arachidonic acid (therefore, the prostaglandins having two double bonds within their structure) play a predominant biological role.
For this reason, we will consider the prostaglandin synthesis process starting from arachidonic acid which, for simplicity, will be summarized in the following main points:
- Arachidonic acid is found within phospholipid membranes in esterified form. The actual arachidonic acid is obtained by the action of phospholipase A2 from the esterified form.
- The arachidonic acid thus released can take different synthetic paths:
- The cyclooxygenase pathway (or cyclic pathway) which leads to the synthesis of prostaglandins and thromboxanes;
- The lipoxygenase pathway (or linear pathway) that leads to the synthesis of leukotrienes.
- Through the action of the enzyme cyclooxygenase (COX), cyclic endoperoxide PGG2 (prostaglandin G2) is obtained from arachidonic acid and, subsequently, with the peroxidase action, cyclic endoperoxide PGH2 (prostaglandin H2).
- From PGH2 it is possible to obtain:
- Prostaglandin E2 (PGE2) by the action of PGE isomerase.
- Prostaglandin F2α (PGF2α) by the action of prostaglandin-F synthase.
- Prostaglandin D2 (PGD2) by the action of another isomerase.
- Prostaglandin I2 (PGI2) - better known as prostacyclin - by the action of prostacyclin synthase.
- Thromboxane A2 (TXA2) by the action of thromboxane synthase.
