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a
b
MT + Enzymes
MT- Enzymes
re-organization of
enzyme associations
decrease/increase in MT
dynamics and stability
metabolite levels
enzyme
activation/inhibition
increased/decreased
metabolic fluxes
altered energy production
pathological inclusions
Fig. 7.4 (a) Microtubule (
red rectangles
) ultrastructures exist in dynamic equilibrium resulting
from the association with enzymes (
green triangles
and
blue squares
). Microtubular systems are
stabilized when these enzymes are either active in catalyzing their cognate reactions (
presence of
star
) or when these enzymes are inactive (
absence of star
). (b) The network of interactions
involved in sensing changes in levels of metabolites by the microtubular cytoskeleton. The
black arrows
represent the flow of information through the network following a change in
metabolite levels. The
dotted red arrow
represents the possible pathological consequences of
perturbations in the network
GTP impedes the association of the MAP TPPP/p25 with the MTs in the mitotic
spindle to arrest mitosis (Tirian et al.
2003
).
7.4 Enzyme Associations in Energy Production
Cells consist of a large number of nonlinearly interacting constituents exhibiting
complex behavior during the course of their intra- and intermolecular com-
munications. Systems Biology is based on a systemic approach to the analysis of
the structural and functional interactions between components rather than on the
analysis of the individual components themselves. Data gathered from the measured
and computed fluxes through a pathway can be integrated and interpreted to obtain
understanding at the system level. A typical example of a system-level concept is the
metabolite channeling occurring in the microcompartments that comprise enzymes
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