{ diff(x1, t) = ((-1)*k32*x1*(k5*x3/(k6 + x3) + k7*x2/(k8 + x2) + k9*x3*x2/((k6 + x3)*(k8 + x2)))*(1 - k10*x1/(k11 + x1) - k12*x4/(k13 + x4))*k4 + (-1)*k32*x1*k4 + 1*k32*k1 + 1*k32*k2*(1 - x1/k3)*x1)/k32,
  diff(x2, t) = (1*k32*k14*(1 - x2/k15)*x2 + (-1)*k32*k16*x2 + 1*k32*k14*(1 - x2/k15)*(k17*x3/(k18 + x3) + k19*x1/(k20 + x1))*x2)/k32,
  diff(x3, t) = (1*k32*k21 + 1*k32*k22*(1 - x3/k23)*x3 + 1*k32*k22*(1 - x3/k23)*k25*x2/(k26 + x2)*x3 + (-1)*k32*k24*x3)/k32,
  diff(x4, t) = ((-1)*k32*k29*x4 + 1*k32*k27*(1 - x4/k28)*x4 + 1*k32*k27*(1 - x4/k28)*k30*x1/(k31 + x1)*x4)/k32 }