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