\frac{dx_{1}}{dt} = 1 \cdot \left(k_{3} \cdot x_{3} - k_{4} \cdot k_{5}^{k_{6}} \cdot x_{1}\right) / k_{2}\\
\frac{dx_{2}}{dt} = 1 \cdot \left(k_{7} \cdot k_{8}^{k_{9}} \cdot x_{3} - k_{10} \cdot x_{2}\right) / k_{2}\\
\frac{dx_{3}}{dt} = \left(-1 \cdot \left(k_{3} \cdot x_{3} - k_{4} \cdot k_{5}^{k_{6}} \cdot x_{1}\right) + -1 \cdot \left(k_{7} \cdot k_{8}^{k_{9}} \cdot x_{3} - k_{10} \cdot x_{2}\right) + -1 \cdot \left(k_{11} \cdot x_{3} - k_{12} \cdot x_{4}\right)\right) / k_{2}\\
\frac{dx_{4}}{dt} = 1 \cdot \left(k_{11} \cdot x_{3} - k_{12} \cdot x_{4}\right) / k_{2}