Chem Phys Lipids 1998 Jun;93(1-2):123-9

The lipase/colipase complex is activated by a micelle: neutron crystallographic evidence.

Pignol D, Hermoso J, Kerfelec B, Crenon I, Chapus C, Fontecilla-Camps JC

Laboratoire de Cristallographie et de Cristallogenese des Proteines, Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS, Grenoble, France.

The catalytic activity of most lipases depends on the aggregation state of their substrates. It is supposed that lipase activation requires the unmasking and structuring of the enzyme's active site through conformational changes involving the presence of oil-in-water droplets. This phenomenon has been called interfacial activation. Here, we report the crystal structure of the pancreatic activated lipase/colipase/micelle complex as determined using the D2O/H2O contrast variation low resolution neutron diffraction method. We find that a disk-shaped micelle interacts extensively with the concave face of colipase (CL) and the distal tip of the C-terminal domain of lipase away from the active site of the enzyme. Such interaction appears to help stabilizing the lipase-CL interaction. Consequently, we conclude that lipase activation is not interfacial but occurs in the aqueous phase and it is mediated by CL and a micelle.

PMID: 9720254, UI: 98386723