Constructing Biological Pathway Models with Hybrid Functional Petri Nets - Biological Petri Nets - page 110

Fig. 12. Simulation results of lacZ − and lacY − mutants. We can see that the glucose is not produced in the lacZ − mutant
and the lactose can not enter a cell in the lacY − mutant.
Behavior of the lac operon mutant
Figure 12 shows the simulation results of the mutants lacZ − and lacY − obtained from GON. From this
figure, we can observe that, in the lacZ − mutant, glucose is never produced again once it is completely
consumed. On the other hand, in the lacY − mutant, the concentration of lactose (inside the cell) never
grows, since lactose can not pass a cell membrane in this mutant. Note that these observations from the
simulation results support the experimental results [Alberts et al., 1994; Lewin, 1997].
CONCLUSION
In this paper, we demonstrated how to construct HFPNs in modeling biological pathways with the
example of the lac operon gene regulatory mechanism and glycolytic pathway. This example was
simulated by GON and the results of five mutants of lac operon gene were shown, which correspond