Katalizujšcymi are enzymes cyclooxygenase metabolism of phospholipids of the cell membrane to the formation of prostanoids ties conducting obejmujšcych prostaglandin and thromboxanes . Prostaglandin kontrolujš variety of physiological processes , such as protection of the gastrointestinal tract, the proper functioning of the kidneys, reproductive processes , and the course of inflammation . It is now known that cyclooxygenase (COX ) is present in at least two isoforms encoded by genes located on different chromosomes . Significant differences between COX variations are also observed at the mRNA level but two isoforms of protein structure is very similar , with podobnš aktywnościš katalitycznš . Cyclooxygenase - 1 (COX -1) is involved in both maintaining homeostasis in normal conditions and in the early stages of an inflammatory reaction (0-1 hours ) . On the other hand, cyclooxygenase - 2 (COX -2) is involved in the later stages of the inflammatory reaction (> 1 hour ) when it comes to the development of the immune response. Recent studies also dowodzš that COX- 2 is involved in the process of extinction of the inflammatory response through production of prostaglandin cyklopentanowych series J ( PGD2 metabolites ) , e.g., 15 - deoxy -D12 , 14PGJ2 . These prostaglandins posiadajš inflammatory properties due to the ability to activate receptors jšdrowych PPAR - g , and / or inhibiting the activity of transcription factor NF-kB . An attempt to explain these opposing activities of COX- 2 has led to the hypothesis put forward that the activity be attributed prozapalnš COX- 2, but with anti-inflammatory properties - the third embodiment of the cyclooxygenase (COX -3). Hypothetical COX - 3 would be structurally similar to COX- 2 , perhaps encoded by the same gene , as its activity was blocked by the selective COX- 2 inhibitors . The implications of this fact in the treatment of inflammatory conditions are discussed in Part II of this article.