Prostaglandins. Chemical nature and the biological significance.
The prostaglandins are a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20carbon atoms, including a 5-carbon ring.
They are mediators and have a variety of strong physiological effects, such as regulating the contraction and relaxation of smooth muscle tissue.[1] Prostaglandins are not endocrinehormones, but autocrine or paracrine, which are locally acting messenger molecules. They differ from hormones in that they are not produced at a discrete site but in many places throughout the human body. Also, their target cells are present in the immediate vicinity of the site of their secretion (of which there are many).
The prostaglandins, together with the thromboxanes and prostacyclins, form the prostanoidclass of fatty acid derivatives, a subclass of eicosanoids.
The abbreviation for "prostaglandin" is PG; specific prostaglandins are named with a letter (which indicates the type of ring structure) followed by a number (which indicates the number of double bonds in the hydrocarbon structure). For example, prostaglandin E1 is abbreviated PGE1 or PGE1, and prostaglandin I2 is abbreviated PGI2 or PGI2. The number is traditionally subscripted when the context allows, but as with many similar subscript-containing nomenclatures, the subscript is simply forgone in many database fields that can store only plain text (such as PubMed bibliographic fields), and readers are used to seeing and writing it without subscript.
Biochemistry
Biosynthesis
Biosynthesis of eicosanoids
Prostaglandins are found in most tissues and organs. They are produced by almost all nucleated cells. They are autocrine and paracrine lipid mediators that act upon platelets, endothelium, uterine and mast cells. They are synthesized in the cell from the essential fatty acids (EFAs).
An intermediate arachidonic acid is created from diacylglycerol viaphospholipase-A2, then brought to either the cyclooxygenase pathway or thelipoxygenase pathway to form either prostaglandin and thromboxane orleukotriene respectively. The cyclooxygenase pathway produces thromboxane,prostacyclin and prostaglandin D, E and F. Alternatively, the lipoxygenase enzyme pathway is active in leukocytes and in macrophages and synthesizes leukotrienes.
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