Fig 6. Number of enzyme targets for VMAT2 and TH.

Optimal drug discovery considered with therapeutic, adverse, and variation effects simultaneously, at the specified number of enzyme targets. The left figure (A) is the case for 95% deficiency of VMAT2, and the right (B) for 100% deficiency of TH, whereas u_t, u_l, and u_d denote the external control for tyrosine, L-DOPA, and intracellular dopamine, respectively. Furthermore, α_j is the enzyme activity for the j^th reaction rate.