\frac{dx_{1}}{dt} = -1 \cdot k_{72} \cdot k_{38} \cdot k_{55} \cdot x_{1} \cdot x_{2} / \left(k_{54} \cdot k_{48} + k_{50} \cdot k_{47} + k_{49} \cdot k_{46}\right) / k_{72}\\
\frac{dx_{2}}{dt} = \left(1 \cdot k_{72} \cdot k_{38} \cdot k_{55} \cdot x_{1} \cdot x_{2} / \left(k_{54} \cdot k_{48} + k_{50} \cdot k_{47} + k_{49} \cdot k_{46}\right) + -1 \cdot k_{72} \cdot \left(k_{54} \cdot \left(k_{53} \cdot k_{62} + k_{52} \cdot k_{59} + k_{51} \cdot k_{56}\right) + k_{50} \cdot \left(k_{53} \cdot k_{61} + k_{52} \cdot k_{58}\right) + k_{49} \cdot \left(k_{53} \cdot k_{60} + k_{52} \cdot k_{57}\right)\right) \cdot x_{2}\right) / k_{72}\\
\frac{dx_{3}}{dt} = \left(1 \cdot k_{72} \cdot \left(k_{54} \cdot \left(k_{53} \cdot k_{62} + k_{52} \cdot k_{59} + k_{51} \cdot k_{56}\right) + k_{50} \cdot \left(k_{53} \cdot k_{61} + k_{52} \cdot k_{58}\right) + k_{49} \cdot \left(k_{53} \cdot k_{60} + k_{52} \cdot k_{57}\right)\right) \cdot x_{2} + -1 \cdot k_{72} \cdot \left(k_{63} + \left(1 - k_{63}\right) \cdot k_{71}\right) \cdot x_{3}\right) / k_{72}\\
\frac{dx_{4}}{dt} = 1 \cdot k_{72} \cdot \left(k_{63} + \left(1 - k_{63}\right) \cdot k_{71}\right) \cdot x_{3} / k_{72}