Study of the influence of ionizing radiation on the activity of the neurotoxin Vipoxin in a model monolayer system at the water/air interface

Abstract

The main components of the cell membrane are phospholipids, and the enzymes that hydrolyze them for the purposes of many important physiological functions are the phospholipases whose properties strongly depend on the phospholipids’ structural organization. Here, we propose a proper experimental approach to study the effect of ionizing radiation on the catalytic action of the neurotoxin Vipoxin, a heterodimeric protein complex composed of an active basic secretory phospholipase A2 (PLA2) and an inactive acidic component, known as “inhibitor”, on the phospholipid substrate such as α-L-dilauroylphosphatidylcholine (DLPC) using as a model system Langmuir monolayer. First, the Vipoxin dissolved in buffer solution was irradiated in a controlled manner with radiation doses varying from 0.1 to 10 Gy, next, the Vipoxin PLA2 activity was followed in real-time, using a modified Langmuir trough, measuring the surface area change of the monolayer. This approach allowed us to obtain the dependence of the neurotoxin catalytic activity at a particular surface pressure and to determine the fundamental constants of the enzyme reaction. It was found that the activity of Vipoxin was influenced in a dose dependent manner. We also found that at higher irradiation doses the enzymatic activity increased, hypothetically due to dissociation of its dimeric Vipoxin complex.

Keywords

• PLA2
• Vipoxin
• Ionizing radiation
• Langmuir monolayer
• Enzyme kinetics