Thermodynamics Research Today is a free monthly online journal that collates and summarizes the latest research about Thermodynamics, including details on enthalpy, entropy, energy transitions.

A thermodynamic study of GPI-anchored and soluble form of alkaline phosphatase films at the air-water interface.

Ronzon F, Rieu JP, Chauvet JP, Roux B

Laboratoire de Physico-Chimie Biologique, UMR 5013, Université Claude Bernard Lyon I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France. frederic.ronzon@sanofi-pasteur.com

Glycosylphosphatidyl inositol (GPI) anchored proteins are localized and clustered on the outer layer of the plasma membranes forming microdomains. Among them, mammalian alkaline phosphatases (AP-GPI) are widely distributed enzymes. They can also exist as soluble proteins without anchor (APs). Using the Langmuir film technique, we study the thermodynamic properties of monolayers for both protein forms at the air-buffer interface. The enzymatic activity is maintained at the interface but the adsorption of the two forms of AP is very different. AP-GPI presents a higher surface activity and a larger molecular area than the soluble form. The molecular area deduced for high surface pressures suggests a different organization of the monolayers for these two forms. APs molecules seem to adsorb as a multilayer at the interface while AP-GPI appear to be orientated with the major axis parallel to the interface. This orientation allows the accessibility of AP-GPI enzymatic sites that are turned in direction of the subphase as in vivo where the active sites must be turned outside of the membrane.

Published 14 August 2006 in J Colloid Interface Sci, 301(2): 493-502.
Full-text of this article is available online (may require subscription).

© 2005-2008 Thermodynamics Research Today. All Rights Reserved.