sodium-dodecyl-sulfate and dioleoylphosphatidic-acid

An anionic surfactant, SDS, is commonly used to model compounds of negatively charged phospholipids. The effect of SDS on the thermal inactivation of BAA (alpha-amylase from Bacillus amyloliquefaciens ) was compared with the effect of negatively charged phospholipid vesicles of DOPA (dioleoylphosphatidic acid) at 40-55 degrees C. The inactivation kinetics revealed that both SDS below its c.m.c. (critical micellar concentration) and DOPA vesicles accelerated the inactivation and the unfolding of the enzyme structure. Both SDS and DOPA vesicles lowered the activation enthalpy and entropy for the inactivation. The lowered activation parameters might be due to the relatively small energy requirement needed to reach the transition state from the ground state of BAA in the presence of the negatively charged hydrophobic environments. This study suggests an accelerated unfolding of BAA in the presence of SDS to be energetically similar to the accelerated unfolding in the presence of DOPA vesicles that involve a molten-globule-like state.

Topics: alpha-Amylases; Animals; Anions; Bacillus; Dihydroxyphenylalanine; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Kinetics; Liposomes; Phosphatidic Acids; Phospholipids; Protein Folding; Sodium Dodecyl Sulfate; Temperature; Water