Discrimination between closed and open forms of lipases using electrophoretic techniques
Updated 11-03-2005 14:07

The enhanced catalytic activity of lipases is often associated with structural changes. The three dimensional (3-D) structures showed that the covalently inhibited lipases exist under their open conformations, in contrast to their native closed forms. We have studied the inhibition of various lipases: Human and Dog gastric lipases (HGL and DGL, respectively), Human pancreatic lipase (HPL) and Humicola lanuigiunosa lipase (HLL) by the octyl-undecyl phosphonate inhibitor and we have measured the subsequent modifications of their respective electrophoretic mobility. Furthermore, the experimental values of the isoelectric points found for the native (closed) and the inhibited (open) lipases are in agreement with theoritical calculations based on the electrostatic potential. We concluded that there is a significant difference in the isoelectric points between the closed (native) and open (inhibited) conformations of the four lipases investigated. Analysis of the electrophoretic pattern is thus proposed as an easy experimental tool to differentiate between a closed and an open form of a given lipase.

Electrostatic potential maps displayed on the molecular surface of the closed (A) and open (B) forms of HPL using the X-plor program . Negative potential is colored black and positive potential, grey. The resulting electrostatic dipole is shown by an arrow.