\frac{dx_{1}}{dt} = \left(1 \cdot k_{16} \cdot k_{17} \cdot k_{28} \cdot x_{3} / \left(k_{19} \cdot k_{18}\right) / \left(\left(1 + k_{28} / k_{19} + k_{21} \cdot x_{5} / k_{20}\right) \cdot \left(1 + x_{3} / k_{18}\right)\right) + -1 \cdot k_{16} \cdot k_{22} \cdot k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11} \cdot \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}\right) / \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}^{2} + k_{10} \cdot \left(1 + k_{15} \cdot x_{3} / k_{14}\right) / \left(1 + x_{3} / k_{14}\right)^{2} \cdot 1 + k_{9} \cdot x_{1} / k_{7} + k_{13} \cdot x_{3} / k_{11} + k_{12} \cdot k_{9} \cdot x_{1} / k_{7} \cdot k_{13} \cdot x_{3} / k_{11}^{2}\right)\right) / k_{16}\\
\frac{dx_{2}}{dt} = \left(1 \cdot k_{16} \cdot k_{22} \cdot k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11} \cdot \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}\right) / \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}^{2} + k_{10} \cdot \left(1 + k_{15} \cdot x_{3} / k_{14}\right) / \left(1 + x_{3} / k_{14}\right)^{2} \cdot 1 + k_{9} \cdot x_{1} / k_{7} + k_{13} \cdot x_{3} / k_{11} + k_{12} \cdot k_{9} \cdot x_{1} / k_{7} \cdot k_{13} \cdot x_{3} / k_{11}^{2}\right) + -1 \cdot k_{16} \cdot k_{23} \cdot x_{2} \cdot x_{6} / \left(k_{24} \cdot k_{25}\right) / \left(\left(1 + x_{2} / k_{24}\right) \cdot \left(1 + x_{6} / k_{25}\right)\right)\right) / k_{16}\\
\frac{dx_{3}}{dt} = \left(-1 \cdot k_{16} \cdot k_{17} \cdot k_{28} \cdot x_{3} / \left(k_{19} \cdot k_{18}\right) / \left(\left(1 + k_{28} / k_{19} + k_{21} \cdot x_{5} / k_{20}\right) \cdot \left(1 + x_{3} / k_{18}\right)\right) + -1 \cdot k_{16} \cdot k_{22} \cdot k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11} \cdot \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}\right) / \left(1 + x_{1} / k_{7} + x_{3} / k_{11} + k_{8} \cdot x_{1} / k_{7} \cdot x_{3} / k_{11}^{2} + k_{10} \cdot \left(1 + k_{15} \cdot x_{3} / k_{14}\right) / \left(1 + x_{3} / k_{14}\right)^{2} \cdot 1 + k_{9} \cdot x_{1} / k_{7} + k_{13} \cdot x_{3} / k_{11} + k_{12} \cdot k_{9} \cdot x_{1} / k_{7} \cdot k_{13} \cdot x_{3} / k_{11}^{2}\right) + 4 \cdot k_{16} \cdot k_{23} \cdot x_{2} \cdot x_{6} / \left(k_{24} \cdot k_{25}\right) / \left(\left(1 + x_{2} / k_{24}\right) \cdot \left(1 + x_{6} / k_{25}\right)\right) + -1 \cdot k_{16} \cdot k_{26} \cdot x_{3} / \left(k_{27} + x_{3}\right)\right) / k_{16}\\
\frac{dx_{4}}{dt} = 0