Prostaglandins cyclooxygenase enzymes

Prostaglandins play an important role in the function of several organ systems. These compounds are synthesized via the interaction of two isoforms of the cyclooxygenase enzyme (COX-1 and COX-2) with their substrate, arachidonic acid (Fig. 55-3). 

FIGURE 55-3. Synthesis pathway for prostaglandins and leukotrienes. COX-2, cyclooxygenase enzyme 2 NSAIDs, nonsteroidal antiinflammatory drugs. (From DiPiro JT, Talbert RL, Yee GC, et al,... 

Cyclooxygenase Enzymes responsible for metabolizing arachidonic acid to prostaglandins. 

An important example of heterogeneous diastereoselective synthesis by catalytic way is the synthesis of prostaglandines (a family of compounds having the 20-carbon skeleton of the prostanoic acid) (Scheme 14.14). Naturally, these molecules are biosynthesized via a cyclooxygenase enzyme system that is widely distributed in mammalian tissues. Many of the synthetic routes [272] involve the diastereoselective hydrogenation of a carbonylic bond having a C=C double bond... 

Q Mechanism of Inhibits the enzyme prostaglandin cyclooxygenase in platelets, which... 

Carey MA, Germolec DR, Langenbach R, Zeldin DC. Cyclooxygenase enzymes in allergic inflammation and asthma. Prostaglandins Leukot Essent Fatty Acids. 2003 69 157-162. 

Sales KJ, Jabbour HN. Cyclooxygenase enzymes and prostaglandins in pathology of the endometrium. Reproduction. 2003 126 559-567. 

Prostaglandin A member of the family of 20-carbon fatty acid compounds (eicosanoids) formed from arachidonic acid by the cyclooxygenase enzyme. Prostaglandins help regulate normal cell activity, and may help mediate certain pathologic responses, including pain, inflammation, fever, and abnormal blood coagulation. 

Studying the biosynthesis of eicosanoids has led to other discoveries as well. For example, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) inactivate the cyclooxygenase enzyme needed for prostaglandin synthesis. In this way, NSAIDs block the synthesis of the prostaglandins that cause inflammation (Section 19.6). 

More recently, it has been discovered that two different cyclooxygenase enzymes, called COX-1 and COX-2, are responsible for prostaglandin synthesis. COX-1 is involved with the usual production of prostaglandins, but COX-2 is responsible for the synthesis of additional prostaglandins in inflammatory diseases like arthritis. NSAIDs like aspirin and ibuprofen inactivate both the COX-1 and COX-2 enzymes. This activity also results in an increase in gastric secretions, making an individual more susceptible to ulcer formation. 

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