Biology Reference
In-Depth Information
it may be reasonable to assume that any
pathway-wide enzyme complexes
such
as (T
X
D
X
)(T
Y
D
Y
) complexes work, at least transiently, as a functional unit
(i.e., as a SOWAN machine). Furthermore, it seems possible that the biochemi-
cal and control behaviors of pathway-wide enzyme complexes (T
X
D
X
)(T
Y
D
Y
)
differ from the behaviors of individual enzymes, T and D, just as quantum dots
true, the Gibbs free energy levels of the (T
X
D
X
)(T
Y
D
Y
) complex may contain
the elements not predictable from the Gibbs free energy levels of its component
enzymes alone.
5. The (T
X
D
X
)(T
Y
D
Y
) complex in Fig.
12.31
can coordinately catalyze the forma-
tion of mRNA
X
and mRNA
Y
(1) if it possesses a set of different conformational
states (or different Gibbs free energy levels or quantum states) and (2) if it can be
thermally excited from any one of these
ground states
with free energy level G
ij
to the common excited state with free energy level G
ij
{
, during the life time of
which the complex can catalyze the coordinated enzymic process (through Step
9 in Fig.
12.27
) with the rate constants determined by
D
G
ij
{
(see also Row 8 in
z
Þ=RT
Ae
ðD
G ij^
k
ij
¼
(12.40)
where
D
G
ij
z
¼
G
z
G
ij
(12.41)
and k
ij
is the rate constant with which two RNA trajectories i and j change in
coordination, and R is the gas constant (which is equal to Nk, where N is the
Avogadro' number and k is the Boltzmann constant), and T is the absolute
temperature. Inserting Eq.
12.41
into
12.40
and dropping the subscript for
brevity leads to:
z
G
Þ=
RT
Ae
ð
G
A
0
e
G
=
RT
k
¼
¼
(12.42)
where A
0
¼
Ae
-G{
which is a constant, since G
{
is assumed to be constant for all
enzymes and enzyme complexes as indicated by the red dotted line in Fig.
12.31
.
Equation
12.42
is identical with the equation derived in Table
11.9
(see Row 8).
The significance of Eq.
12.42
is that:
The rate constant of an enzyme is the exponential function of its ground-state Gibbs free
energy level, G, and not the Gibbs free energy level of the activated states, G
{
.
(12.43)
The justification of Statement 12.43 derives from the fitting of the single-
molecule enzymic data of cholesterol oxidase to the blackbody radiation-like
6. The interiors of Table
12.11
and Fig.
12.30c
deal with the
rates
of changes in
RNA levels, denoted as dTL/dt, where TL stands for transcript level, while the
margins of these tables and Fig.
12.31
address the
Gibbs free energy levels
of
