Question

Among the many fatty acids, ________ serves as an important precursor of eicosanoids such as thromboxane and prostaglandin. They are important for scar healing and uterus contraction but also cause unnecessary inflammations and pains. The two main enzymes involved in production of eicosanoids are lipoxygenase and _____________, which are important drug targets.

Select one:

a. palmitoic acid ;;; cyclooxygenase

b. palmitoic acid ;;; hydroperoxidase

c. arachidonic acid ;;; hydroperoxidase

d. arachidonic acid ;;; cyclooxygenase

e. None of these

Answer 1

Answer ) d arachidonic acid .. cyclooxygenase

EXPLANATION

Eicosanoids are very potent biological signalling molecule. They act as short range Messenger. Arachidonic acid is polyunsaturated fatty acid consist of 20 carbon and is prescursor for eicosanoids such as prostaglandin and thromboxane.

Prostaglandin stimulate uterine contraction, lower blood pressureessure, vasodilation inflammation and pain. The enzyme prostaglandin H2 synthase which is known as cyclooxygenase (Cox) convert the arachidonic acid into prostaglandin G2 ( PGG2) by catalysing the introduction of oxygen and cyclization of carbon atom of arachidonic acid in the double bond position at C-8 and C-11. Further through the peroxidase activity of cyclooxygenase PGG2 is converted into prostaglandin H2 (PGH2)

Thromboxane is derived from prostaglandin in the blood platelets through the use of thromboxane synthase which convert PGH2 into thromboxane A2. Thromboxane act as vasconstrictor and stimulator of platelets aggregation during blood clotting.

An analgesic, antipyretic and anti inflammatory drug aspirin inhibit the synthesis of prostaglandin through irreversible inhibit cyclooxygenase by acetylation of serine residue which is present at the active site of cyclooxygenase enzyme. One of non steroidal anti inflammatory drug (NSAID) is ibuprofen which also inhibit the cyclooxygenase through reversible competition.