Differential scanning calorimetry of the effects of Ca2+ on the thermal unfolding of Pseudomonas cepacia lipase.
Thermal unfolding of P. cepacia lipase was observed by adiabatic differential scanning microcalorimetry in the absence and presence of calcium ions at pH 8, and thermodynamic parameters of unfolding were evaluated to analyze the unfolding mechanism of the enzyme. The temperature of unfolding was higher at higher concentrations of Ca2+. From the Ca2+ concentration-dependence of the unfolding temperature, the number of calcium ions that dissociated from the enzyme molecule upon unfolding was estimated to be one. These results confirmed the validity of the unfolding mechanism proposed previously: NCa2+ < = => D + Ca2+, where N and D represent the native and denatured states, respectively, of the enzyme.
Tanaka
Akiyoshi
A
Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan. akiyoshi@bio.mie-u.ac.jp
Sugimoto
Hayuki
H
Muta
Yuko
Y
Mizuno
Takafumi
T
Senoo
Keishi
K
Obata
Hitoshi
H
Inouye
Kuniyo
K
D016956:Burkholderia cepacia / Q000201:enzymology*; D002118:Calcium / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D005612:Freeze Drying; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D013696:Temperature
D008049:Lipase; D002118:Calcium