Thermal inactivation of the plasma membrane H+-ATPase from Kluyveromyces lactis. Protection by trehalose.
The activity of the isolated plasma membrane H+-ATPase from Kluyveromyces lactis was measured during incubation at 35-45 degrees C and in the absence or in the presence of 0-0.6 M trehalose. As the temperature of incubation was raised from 35 to 45 degrees C, increasing enzyme inactivation rates were observed. Thermal inactivation kinetics of the H+-ATPase were biphasic exhibiting a first rapid phase and then a second slow phase. The transition from the native state occurred through a temperature-mediated increase in the inactivation rate constants of both phases. A model is proposed where the native H+-ATPase yields a partially active intermediary during the first phase of inactivation and then the intermediary is slowly converted into a totally inactive enzyme in the second phase. At each of these temperatures trehalose protected the enzymatic activity in a concentration dependent manner. Full protection was observed at 0.6 M trehalose in the range of 35-40 degrees C. Whereas, at 42 and 45 degrees C, the trehalose-mediated thermoprotection of the H+-ATPase was only partial. Trehalose stabilized the enzyme mainly by preventing the temperature dependent increase of the first and second inactivation rate constants.
Sampedro
J G
JG
Department of Biochemistry, Instituto de Fisiología Celular, Univerisidad Nacional Autónoma de México, Mexico City.
Cortés
P
P
Muñoz-Clares
R A
RA
Fernández
A
A
Uribe
S
S
D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D007716:Kluyveromyces / Q000201:enzymology*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014199:Trehalose / Q000494:pharmacology*
D014199:Trehalose; D006180:Proton-Translocating ATPases