Cyclooxygenase-2 (COX?2) is an enzyme that is activated after an injury. When it

Question

Cyclooxygenase-2 (COX?2) is an enzyme that is activated after an injury. When it is expressed, arachidonic acid is
converted to prostaglandins. These prostaglandins produce inflammatory reactions such as pain, swelling, and
fever. Both Tylenol and aspirin are inhibitors of COX-2 when the enzyme is inhibited, pain is reduced.

a. What is an enzyme and how would COX-2 help the conversion of arachidonic acid -> prostaglandins
proceed? Be sure to include information about the structure of an enzyme

b. Name the substrate for cyclooxygenase-2 (given the information provided).

c. Tylenol is a competitive inhibitor of COX-2, while aspirin is an allosteric inhibitor of the enzyme.
Explain the function of an inhibitor and the differences between competitive and allosteric inhibitors.

Explanation / Answer

a. An enzyme is a chemical substance that act as biological catalysts. A catalyst increases the rate of reaction, but do not participate in the reaction. Cyclooxygenase -2 (COX-2) also known as prostaglandin endoperoxide synthase -2 (PTGS-2) is a biological catalyst that converts arachidonic acid into PGG2 and then reduced to PGH2, then PGH2 is converted into prostaglandins.

b. Arachidonic acid is the substrate of COX-2. It is an unsaturated fatty acid derived from injured plasma membrane.

c. An inhibitor molecule is the one that binds to the enzyme and inhibits its function. The major difference between competitive inhibitor and allosteric inhibitor is competitive inhibitor such as aspirin binds to the active site of an enzyme, whereas an allosteric inhibitor binds to other than active site of an enzyme.

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