{ diff(x1, t) = (1*k23*x4*x12 + (-1)*k24*x1)/k2,
  diff(x2, t) = 0/k2,
  diff(x3, t) = ((-1)*(k11*x4*x3 - k12*x15) + 1*k21*x14*x2/(k22 + x14))/k2,
  diff(x4, t) = (1*k7*x6*x7/(k8 + x6) + (-1)*k9*x4*x5/(k10 + x4) + (-1)*(k11*x4*x3 - k12*x15) + 1*k21*x14*x2/(k22 + x14))/k2,
  diff(x5, t) = 0/k2,
  diff(x6, t) = ((-1)*k7*x6*x7/(k8 + x6) + 1*k9*x4*x5/(k10 + x4))/k2,
  diff(x7, t) = 1*exp(k4 - (x10/k6)^(9/5))*k3*(x10/k5)^(4/5)*(k4 - (x10/k6)^(9/5))/k2,
  diff(x8, t) = (-1)*k25/k2,
  diff(x9, t) = (-1)*exp(k4 - (x10/k6)^(9/5))*k3*(x10/k5)^(4/5)*(k4 - (x10/k6)^(9/5))/k2,
  diff(x10, t) = 1*k25/k2,
  diff(x11, t) = 0/k2,
  diff(x12, t) = ((-1)*k23*x4*x12 + 1*k24*x1)/k2,
  diff(x13, t) = (1*k13*x15*x1/(k14 + x15) + (-1)*k15*x13*x11/(k16 + x13) + (-1)*k17*x13*x2/(k18 + x13) + 1*k19*x14*x2/(k20 + x14))/k2,
  diff(x14, t) = (1*k15*x13*x11/(k16 + x13) + (-1)*k19*x14*x2/(k20 + x14) + (-1)*k21*x14*x2/(k22 + x14))/k2,
  diff(x15, t) = (1*(k11*x4*x3 - k12*x15) + (-1)*k13*x15*x1/(k14 + x15) + 1*k17*x13*x2/(k18 + x13))/k2,
  diff(x16, t) = 0/k1 }