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