From Cellular Function to Industrial Products
33
a.
Q." O)
Q r
& ^
< 3-
* 4
6
*
-50
50
100
Tim e (s)
*!
f
150
200
Q
.
Q _
< ~
g f ?
< D
0
B
1
8
II
r
-50
B
0
50
100
Tim e (s)
0,8
c
Ui
0,7 a j p
1
0,6
50
100
Tim e (s)
200
Figure 2.7 Rapid dynamics of adenylate concentrations. When a pulse of glucose is applied to an energy-
starved continuous culture, the levels of all intermediate metabolites in the EMP pathway experience rapid
changes. The data shown are obtained from a steady-state culture of
S. cerevisiae
pulsed with 1 g L
1
glucose. The rapid sampling technique and the analytical methods are described in Theobald,
et al.
(1993).
Within the first 5 s of the transient, the ATP concentration of the whole cell has decreased by 30%. An
even more pronounced drop in cytoplasmic ATP (different from the overall cell concentration due to the
ATP involving reactions in the mitochondria) is observed. This precipitous drain of ATP must be due to the
rapid formation of glucose-
6
-phosphate and the subsequent formation of fructose-1,6-diphosphate. ADP
peaks after less than 5 s and is slowly consumed in the last reactions of the EMP pathway or by
mitochondrial processes. Note that the ATP concentration has not reached the steady-state level even after 3
min, while the energy charge is back in the 0.85-0.90 range after less than 1
min. On the time scale of the
growth process (i.e. from 1 hour and up) a pseudo steady-state assumption (see also Eq. (5.2)) for all
adenylate concentrations is certainly satisfied. The data are from Theobald
et al. (
1997).
A. Total concentrations of ATP (•), ADP ( ■) and AMP ( )
B. Cytoplasmic concentrations of ATP ( • ) and ADP ( ■)
C. Energy charge
200
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