Thermodynamic properties of the cholesterol transfer reaction from liposomes to cytochrome P450 scc: An enthalpy-entropy compensation effect

Abstract

We have investigated the thermodynamic properties of the cholesterol transfer reaction from various types of liposomes to purified steroid-free cytochrome P450 scc. From the results of temperature effect on the reaction, we obtained ΔG+, ΔH+, and ΔS+ values for the reaction with various phosphatidylcholine vesicles containing different fatty acyl chains. The plots of ΔH+ against ΔS+, and ΔG+ against ΔH+ both reveal that an enthalpyentropy compensation effect was seen in a series of phospholipid and micellar media of cholesterol. Our β-value of 420° K is unusually high among reported values for biochemical reactions.