?Effect of polar head groups on the activity of aspartylprotease adsorbed to lipid membranes?

MARTINI, F.; E. A. DISALVO

CHEMISTRY AND PHYSICS OF LIPIDS

ELSEVIER IRELAND LTD

Año: 2003 vol. 122 p. 177 - 184

0009-3084

The proteolytic activity of an aspartyl protease of Mucor miehei was correlated with the adsorption of the protease to lipid vesicles. It was observed that the presence of phosphatidylethanolamines (PE´s) in the membrane increased the enzyme activity in a 20% in the gel phase and 10% in the fluid phase. The effects of protease on the surface pressure of monolayers composed by dioleoylphosphatidylcholine (DOPC), dimyristoylphosphatidylcholine (DMPC), dimyristoyl phosphatidylethanolamine (DMPE) were measured at constant temperature as a function of the surface pressure. At low surface pressures, the major changes were induced by protease on DOPC and DMPC monolayers. However, the effect were much lower when the monolayer was composed by DMPE. The low hydration and strong head-head interaction between the phosphates and the amine groups of adjacent PE´s would result in an area per molecule much lower in PE than in phosphatidylcholine (PC) in concordance with the lower penetration in PE. Protease adsorption on PE membranes increases the proteolytic activity in which condition is less susceptible to inhibition by pepstatin. However, PC´s do not alter the enzyme activity being the action of inhibitor unaffected