A continuous spectrophotometric assay for phospholipase A(2) activity.

Area of Science:

• Biochemistry
• Enzymology

Background:

• Phospholipase A(2) (PLA(2)) plays a critical role in various biological processes.
• Accurate and efficient methods for quantifying PLA(2) activity are essential for research and drug discovery.

Purpose of the Study:

• To develop a simple, continuous, and cost-effective spectrophotometric method for assaying phospholipase A(2) activity.
• To characterize the kinetic parameters and optimal conditions for the developed assay.

Main Methods:

• A coupled enzymatic assay was employed using dilinoleoyl phosphatidylcholine as the substrate for PLA(2) and lipoxygenase as the coupling enzyme.
• PLA(2) activity was monitored spectrophotometrically by measuring the increase in absorbance at 234 nm, corresponding to hydroperoxide formation from linoleic acid.
• Optimal concentrations of hog pancreatic PLA(2), lipoxygenase, pH, and deoxycholate were determined.

Main Results:

• The assay demonstrated specificity and high sensitivity for PLA(2) activity.
• Optimal conditions included pH 8.5 and 3mM deoxycholate.
• Phospholipid hydrolysis followed Michaelis-Menten kinetics with V(m)=1.8 microM/min and K(m)=4.5 microM.
• The method is suitable for studying PLA(2) inhibitors.

Conclusions:

• A simple, rapid, and cost-effective continuous spectrophotometric assay for PLA(2) activity has been established.
• The assay utilizes inexpensive, non-radiolabeled natural substrates, making it widely accessible.
• This method provides a valuable tool for biochemical research and the screening of PLA(2) inhibitors.