Lysophospholipase--transacylase from rat lung: isolation and partial purification

Area of Science:

• Biochemistry
• Enzymology
• Pulmonary Research

Background:

• Phosphatidylcholine is a key component of pulmonary surfactant, essential for lung function.
• Lysophospholipids are intermediates in phospholipid metabolism and can be toxic at high concentrations.

Purpose of the Study:

• To investigate the enzymatic activities present in rat lung supernatant responsible for lysophospholipid metabolism.
• To characterize the enzyme responsible for both lysophospholipase and transacylase activities.

Main Methods:

• Incubation of rat lung supernatant with a radiolabeled phospholipid substrate.
• Enzyme purification and characterization, including molecular weight estimation.
• Analysis of enzyme activity ratios and substrate specificity.

Main Results:

• A single soluble enzyme, provisionally named lysophospholipase-transacylase, was identified.
• The enzyme exhibited approximately threefold higher lysophospholipase activity than transacylase activity.
• Purified enzyme (approx. 250-fold) synthesized disaturated phosphatidylcholine, a crucial surfactant component.
• Acyl chain selectivity was observed during the transacylase activity.

Conclusions:

• A single enzyme in rat lung possesses both lysophospholipase and transacylase activities.
• This enzyme contributes to the synthesis of disaturated phosphatidylcholine, vital for pulmonary surfactant.
• The identified enzyme differs from other purified lysophospholipases lacking transacylase activity.