The enzymatic action of Vipoxin on insoluble long-chain phospholipid Langmuir monolayers

Abstract

In recent years some toxins such as Vipoxin that is isolated from the venom of Vipera ammodytes meridionalis have provoked scientific interest due to their intriguing structure, enzymatic activities, and potential for medical applications. This paper considers the kinetics of the enzymatic action of Vipoxin on long-chain phospholipids’ monolayers of Palmitoyl-oleoyl-phosphatidyl-choline (POPC), Palmitoyl-oleoyl-phosphatidyl-glycerol (POPG), and Palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) spread at air-water interfaces. To analyze theoretically the enzyme activity that is altered by the presence of insoluble lipolytic products we adapted the classical Michaelis-Menten kinetic model and an experimental approach that utilizes the β- cyclodextrin ( β-CD ) as a solubilizing agent. This allowed us to obtain the global kinetic constants of the enzymatic reaction catalyzed by the Vipoxin. Using AFM, we also analyzed the influence of the monolayer structure on the kinetics of the enzyme reaction by measuring the observed structures and microheterogeneities of the LB films transferred from monolayers that either contained β-CD or without β-CD . • Kinetics of the enzymatic action of Vipoxin on long-chain phospholipid monolayers is studied. • An adapted Michaelis-Menten kinetic model for fitting the data is applied. • The global kinetic constants of Vipoxin action are obtained. • The interfacial behavior of studied systems is visualized by AFM.