An alternative approach to Michaelis-Menten kinetics that is based on the Renormalization Group: Comparison with the perturbation expansion beyond the sQSSA

TL;DR

This paper introduces a renormalization group-based approach to Michaelis-Menten kinetics, providing more accurate uniform approximations than traditional perturbation methods, especially for challenging parameter regimes.

Contribution

It applies the SPDERG method to Michaelis-Menten kinetics, offering simpler equations and improved approximations over perturbation expansions beyond sQSSA.

Findings

Second order SPDERG approximations match known perturbation results

Simpler differential equations within SPDERG approach

Enhanced accuracy in reproducing numerical solutions

Abstract

We recall the perturbation expansion for Michaelis-Menten kinetics, beyond the standard quasi-steady-state approximation (sQSSA). Against this background, we are able to appropriately apply the alternative approach to the study of singularly perturbed differential equations that is based on the renormalization group (SPDERG), by clarifying similarities and differences. In the present demanding situation, we directly renormalize the bare initial condition value for the substrate. Our main results are: i) the 2nd order SPDERG uniform approximations to the correct solutions contain, up to 1st order, the same outer components as the known perturbation expansion ones; ii) the differential equation to be solved for the derivation of the 1st order outer substrate component is simpler within the SPDERG approach; iii) the approximations better reproduce the numerical solutions of the original problem in a region encompassing the matching one, because of the 2nd order terms in the inner components, calculated here for the first time to our knowledge: iv) the refined SPDERG uniform approximations, that we propose, give the correct asymptotically vanishing solutions, too, and allow to obtain results nearly indistinguishable from the solutions of the original problem in a large part of the whole relevant time window, even in the studied unfavourable kinetic constant case, for an expansion parameter value as large as {\epsilon} = 0.5.