Similarities between the thermal inactivation kinetics of Bacillus amyloliquefaciens alpha-amylase in an aqueous solution of sodium dodecyl sulphate and the kinetics in the solution of anionic-phospholipid vesicles.
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.
Tanaka
Atsushi
A
Wakayama Research Laboratories, Kao Corporation, 1334 Minato, Wakayama-shi, Wakayama 640-8580, Japan. tanaka.atushi@kao.co.jp
Hoshino
Eiichi
E
D000818:Animals; D000838:Anions / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D004295:Dihydroxyphenylalanine / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007700:Kinetics; D008081:Liposomes; D010712:Phosphatidic Acids / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D017510:Protein Folding; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry; D000516:alpha-Amylases / Q000737:chemistry* / Q000378:metabolism*
D000838:Anions; D008081:Liposomes; D010712:Phosphatidic Acids; D010743:Phospholipids; D014867:Water; C037657:dioleoylphosphatidic acid; D012967:Sodium Dodecyl Sulfate; D004295:Dihydroxyphenylalanine; D000516:alpha-Amylases