{ diff(x1, t) = ((-1)*k1*k2*x1/((1 + (x8/k3)^k4)*(k5 + x1)) + 1*k1*k6*x2/(k7 + x2))/k1,
  diff(x2, t) = (1*k1*k2*x1/((1 + (x8/k3)^k4)*(k5 + x1)) + (-1)*k1*k6*x2/(k7 + x2))/k1,
  diff(x3, t) = ((-1)*k1*k8*x2*x3/(k9 + x3) + 1*k1*k14*x4/(k15 + x4))/k1,
  diff(x4, t) = (1*k1*k8*x2*x3/(k9 + x3) + (-1)*k1*k10*x2*x4/(k11 + x4) + 1*k1*k12*x5/(k13 + x5) + (-1)*k1*k14*x4/(k15 + x4))/k1,
  diff(x5, t) = (1*k1*k10*x2*x4/(k11 + x4) + (-1)*k1*k12*x5/(k13 + x5))/k1,
  diff(x6, t) = ((-1)*k1*k16*x5*x6/(k17 + x6) + 1*k1*k22*x7/(k23 + x7))/k1,
  diff(x7, t) = (1*k1*k16*x5*x6/(k17 + x6) + (-1)*k1*k18*x5*x7/(k19 + x7) + 1*k1*k20*x8/(k21 + x8) + (-1)*k1*k22*x7/(k23 + x7))/k1,
  diff(x8, t) = (1*k1*k18*x5*x7/(k19 + x7) + (-1)*k1*k20*x8/(k21 + x8))/k1 }