[ Diff(x[1], t) = (-1)*k[72]*k[38]*k[55]*x[1]*x[2]/(k[54]*k[48] + k[50]*k[47] + k[49]*k[46])/k[72],
  Diff(x[2], t) = (1*k[72]*k[38]*k[55]*x[1]*x[2]/(k[54]*k[48] + k[50]*k[47] + k[49]*k[46]) + (-1)*k[72]*(k[54]*(k[53]*k[62] + k[52]*k[59] + k[51]*k[56]) + k[50]*(k[53]*k[61] + k[52]*k[58]) + k[49]*(k[53]*k[60] + k[52]*k[57]))*x[2])/k[72],
  Diff(x[3], t) = (1*k[72]*(k[54]*(k[53]*k[62] + k[52]*k[59] + k[51]*k[56]) + k[50]*(k[53]*k[61] + k[52]*k[58]) + k[49]*(k[53]*k[60] + k[52]*k[57]))*x[2] + (-1)*k[72]*(k[63] + (1 - k[63])*k[71])*x[3])/k[72],
  Diff(x[4], t) = 1*k[72]*(k[63] + (1 - k[63])*k[71])*x[3]/k[72] ]