{ diff(x1, t) = ((-1)*k1*x1/(k2 + x1) + (-1)*k3*x1*x2/(k6 + k4*x2 + k5*x1 + x1*x2) + 1*k7*x3/(k8 + x3))/k10,
  diff(x2, t) = (1*k1*x1/(k2 + x1) + (-1)*k3*x1*x2/(k6 + k4*x2 + k5*x1 + x1*x2))/k10,
  diff(x3, t) = (2*k3*x1*x2/(k6 + k4*x2 + k5*x1 + x1*x2) + (-1)*k7*x3/(k8 + x3))/k10,
  diff(x4, t) = (1*k7*x3/(k8 + x3) + (-1)*k9*x4)/k10,
  diff(x5, t) = (-1)*k9*x4/k10,
  diff(x6, t) = 0 }