  It is well known in enzyme kinetics that the Michaelis-Menten (MM) equation
is applicable only to enzymes in the steady state. We show that the result
obtained in the previous work [Phys. Rev. Lett. 107, 218301 (2011)] is
inconsistent with the MM equation, not because the authors considered the
enzyme system at mesoscopic concentrations but because they considered the
enzyme system in the non-stationary state. The substrate concentration
dependence of the mean turnover time is, in fact, consistent with the MM
equation in the steady state, regardless of the number of enzymes in the
system.
