A comparative study on kinetics and substrate specificities of Phospholipase A₁ with Thermomyces lanuginosus lipase

The mechanism of lipase binding to the lipid-water interface is crucial for substrate specificity and kinetic properties. In this study, the chain-length specificity, regiospecificity and substrate specificity of Phospholipase A₁ (PLA₁) and its parent enzyme Thermomyces lanuginosus lipase (TLL) have been investigated using a classical emulsion system. The results show that both PLA₁ and TLL are 1,3-regioselective lipases. Additionally, the hydrolytic activity of PLA₁ is comparatively lower on short-chain triacylglyceride (TAG) and higher on phosphatidylcholine (PC) than the hydrolytic activity of TLL. Further, the results obtained with monolayer film techniques demonstrate that the C-terminal region regulates the binding of PLA₁ to PC. A hypothesis is presented according to which the α9 helix of C-terminal region in PLA₁ not only controls the opening of lid but also serves as a membrane anchor that assists in binding to PC. These findings bring new insight into rational design of novel lipases with intriguing functionalities.