desaturase-knockout cells showed phase transition temperature measured by DSC
around 20
C. When temperature of culture was lowered to 25
C, phase transition
temperature of wild type cells was lowered but effect of lowering phase transition
temperature was reduced in the desaturase-knockout cells. The result indicates
desaturases directly alters phase transition temperature of biomembranes. Change
of phase transition temperature caused by desaturase also induces phase separation
in biomembranes as shown in Fig. 8.6. Phase separation is observed as smooth area
Time of culture after temprature shift [h]
0
5
10
15
20
25
Activity of fatty acid desaturases
[nmol/min/mgprotein]
0
5
10
15
20
Palmitate desaturase
Oleate desaturase
Stearate desaturase
Fig. 8.3 Activation of
various desaturases by
lowering temperature of
culture
Temporal changes of fatty
acid desaturases were
measured after lowering
temperature of Tetrahymena
cells from 39.5
C to15
C
Time of cultue after temperature shift [h]
Content of fatty acids [%]
10
20
30
50
40
0
5
10
15
20
25
C14:0+C16:0
C16:1+C18:1
C16:2+C18:2+C18:3
Fig. 8.4 Change of fatty
acid composition in
Tetrahymena cells by
lowering culture
temperature
Culture-temperature of
Tetrahymena cells was
lowered from 39.5
C to
15
C and the culture was
continued. Lipids were
extracted from the cells and
temporal change of fatty
acid composition was
obtained from GLC
measurements
164
8 Global Environment and Biophysics