\frac{dx_{1}}{dt} = 0\\ \frac{dx_{2}}{dt} = \left(1 \cdot k_{15} \cdot k_{7} \cdot \left(1 - k_{9} \cdot x_{2}\right) \cdot x_{2} + -1 \cdot k_{15} \cdot k_{8} \cdot x_{5} \cdot x_{2} / \left(k_{10} + x_{2}\right)\right) / k_{15}\\ \frac{dx_{3}}{dt} = 0\\ \frac{dx_{4}}{dt} = \left(1 \cdot k_{15} \cdot \left(k_{14} + k_{12} \cdot x_{5} \cdot x_{2} / \left(k_{13} + x_{2}\right)\right) + -1 \cdot k_{15} \cdot k_{11} \cdot x_{4}\right) / k_{15}\\ \frac{dx_{5}}{dt} = \left(1 \cdot k_{15} \cdot \left(k_{6} + k_{3} \cdot x_{2} + k_{4} \cdot x_{5} \cdot x_{4} / k_{5}\right) + -1 \cdot k_{15} \cdot k_{2} \cdot x_{5}\right) / k_{15}