Question

The venom of the Eastern diamondback rattler and the Indian cobra contains phospholipase A2, which catalyzes the hydrolysis of fatty acids at the C-2 position of glycerophospholipids. The phospholipid breakdown product of this reaction is lysolecithin (lecithin is phosphatidylcholine). At high concentrations, this and other lysophospholipids act as detergents, dissolving the membranes of erythrocytes and lysing the cells. Extensive hemolysis may be life-threatening.

(a) All detergents are amphipathic. What are the hydrophilic and hydrophobic portions of lysolecithin?

(b) The pain and inflammation caused by a snake bite can be treated with certain steroids. What is the basis of this treatment?

(c) Though the high levels of phospholipase A2 in venom can be deadly, this enzyme is necessary for a variety of normal metabolic processes. What are these processes?

Answer 1

a) Lysolecithins refers to the compounds, which are obtained from phosphatidylcholine, it is amphipathic in nature and comprises both the hydrophobic and hydrophilic regions.  

On the basis of the composition of a lysolecithin, the choline, glycerol, and phosphate are hydrophilic in nature, while the fatty acid on C1 is hydrophobic.  

b). Pain and swelling typically due to release of prostaglandins by the cell. Steroid drugs like Prednisone and Prednisolone act by inhibiting the release of arachidonate by phospholipase A2 form the cellular membrane, thus stopping the synthesis and release of the prostaglandins

c) . Phospholipase refers to an enzyme, which functions on phospholipids and discharges fatty acid from the 2nd carbon of glycerol resulting in the formation of common arachidonic acid and lysophospholipids.  

The phospholipase A2 comprises 15 groups out of which four are very essential, that is, cellular phospholipase A2, secreted phospholipase A2, calcium-independent phospholipase A2, and lipoprotein-associated phospholipase A2.  

They perform essential functions like pro-inflammatory activity, antimicrobial actions, bone formation, insulin secretion, apoptosis, axon regeneration, sperm development, and also function as markers of coronary heart disease.