{ diff(x1, t) = ((-1)*k1*k4*x1/k2/((1 + x1/k2)*(1 + x8/k3)) + 1*k1*k18*x9*x2/k17/(1 + x2/k17))/k1,
  diff(x2, t) = (1*k1*k4*x1/k2/((1 + x1/k2)*(1 + x8/k3)) + (-1)*k1*k18*x9*x2/k17/(1 + x2/k17))/k1,
  diff(x3, t) = ((-1)*k1*k8*x2*x3/k6/(1 + x3/k6 + x4/k6)*(1 + k5*x8/k7)/(1 + x8/k7) + 1*k1*k22*x10*x4/k21/(1 + x5/k21 + x4/k21))/k1,
  diff(x4, t) = (1*k1*k8*x2*x3/k6/(1 + x3/k6 + x4/k6)*(1 + k5*x8/k7)/(1 + x8/k7) + (-1)*k1*k12*x2*x4/k10/(1 + x4/k10 + x3/k10)*(1 + k9*x8/k11)/(1 + x8/k11) + 1*k1*k20*x10*x5/k19/(1 + x5/k19 + x4/k19) + (-1)*k1*k22*x10*x4/k21/(1 + x5/k21 + x4/k21))/k1,
  diff(x5, t) = (1*k1*k12*x2*x4/k10/(1 + x4/k10 + x3/k10)*(1 + k9*x8/k11)/(1 + x8/k11) + (-1)*k1*k20*x10*x5/k19/(1 + x5/k19 + x4/k19))/k1,
  diff(x6, t) = ((-1)*k1*k14*x5*x6/k13/(1 + x6/k13 + x7/k13) + 1*k1*k26*x11*x7/k25/(1 + x8/k25 + x7/k25) + (-1)*k1*(k36*x6 - k37*x17))/k1,
  diff(x7, t) = (1*k1*k14*x5*x6/k13/(1 + x6/k13 + x7/k13) + (-1)*k1*k16*x5*x7/k15/(1 + x6/k15 + x7/k15) + 1*k1*k24*x11*x8/k23/(1 + x8/k23 + x7/k23) + (-1)*k1*k26*x11*x7/k25/(1 + x8/k25 + x7/k25) + (-1)*k1*(k38*x7 - k39*x18))/k1,
  diff(x8, t) = (1*k1*k16*x5*x7/k15/(1 + x6/k15 + x7/k15) + (-1)*k1*k24*x11*x8/k23/(1 + x8/k23 + x7/k23) + (-1)*k1*(k27*x8 - k28*x12))/k1,
  diff(x9, t) = 0/k1,
  diff(x10, t) = 0/k1,
  diff(x11, t) = 0/k1,
  diff(x12, t) = (1*k1*(k27*x8 - k28*x12) + (-1)*k1*k42*x19*x12/k43/(1 + x12/k43 + x18/k44))/k1,
  diff(x13, t) = (1*k1*k29*x12^k30/(k31^k30 + x12^k30) + (-1)*k1*k32*x13)/k1,
  diff(x14, t) = (1*k1*k32*x13 + (-1)*k1*k33*x14)/k1,
  diff(x15, t) = (1*k1*k34*x14 + (-1)*k1*k35*x15 + (-1)*k1*(k40*x15 - k41*x19))/k1,
  diff(x16, t) = 0/k1,
  diff(x17, t) = (1*k1*(k36*x6 - k37*x17) + 1*k1*k45*x19*x18/k46/(1 + x18/k46 + x12/k47))/k1,
  diff(x18, t) = (1*k1*(k38*x7 - k39*x18) + 1*k1*k42*x19*x12/k43/(1 + x12/k43 + x18/k44) + (-1)*k1*k45*x19*x18/k46/(1 + x18/k46 + x12/k47))/k1,
  diff(x19, t) = (1*k1*(k40*x15 - k41*x19) + (-1)*k1*k48*x19)/k1 }