Standardization of lipid sample preparation for monitoring phospholipase activity

Phospholipase enzymes, such as A1, A2, B, and D, are found in the venom of venomous animals, including brown spiders. Phospholipase D (PLD) isoforms from brown spider venom can cause dermonecrosis, hemolysis, and nephrotoxicity. New methods to monitor PLD activity are essential for understanding its mechanisms and molecular characteristics. One effective approach is using ³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy to track PLD enzymatic activity by identifying the ³¹P signals of phosphorylated substrates and products. However, sample preparation for ³¹P NMR is challenging, as the lipid substrates' carbon chain length and unsaturation degree can affect solubilization, oxidation, and enzyme interaction, impacting the reaction kinetics. This study standardizes a phospholipid sample preparation method with fatty acids of different chain lengths for monitoring PLD activity. The addition of CHAPS detergent is essential for solubilizing lipids with long-chain fatty acids, but its concentration needs optimization, as higher amounts can inhibit PLD activity. Storing lipids in ethanol, forming lipid films, and injecting nitrogen into stock solutions improved lipid quantification and assay reproducibility. These standardized conditions can be adapted to other experimental approaches for monitoring phospholipase activity.