Inherent fluctuations may play an important role in biochemical and biophysical systems when the system involves some species with low copy numbers. This talk will present the recent work on the stochastic modeling of enzyme-catalyzed reactions in biology.

In the first part of the talk, I will introduce a multiscale approximation method that helps reduce network complexity using various scales in species numbers and reaction rate constants. I will apply the multiscale approximation method to simple enzyme kinetics and derive quasi-steady-state approximations. In the second part of the talk, I will show another example for glucose metabolism where we see different-sized enzyme complexes. We hypothesized that the size of multienzyme complexes is related to their functional roles. We will see two models: one using a system of ordinary differential equations and the other using the Langevin dynamics.