Molecular Dynamics Simulations on Aspergillus niger Monoamine Oxidase: Conformational Dynamics and Inter-monomer Communication Essential for Its Efficient Catalysis

Abstract

Aspergillus niger Monoamine Oxidase (MAO-N) is a homodimeric enzyme responsible for the oxidation of amines into the corresponding imine. Laboratory evolved variants of MAO-N in combination with a non-selective chemical reductant represents a powerful strategy for the deracemisation of chiral amine mixtures and, thus, is of interest for obtaining chiral amine building blocks. As we reported recently, MAO-N presents a rich conformational dynamics with a flexible β-hairpin region that can adopt closed, partially closed and open states. Despite the β-hairpin conformational dynamics is altered along the laboratory evolutionary pathway of MAO-N, the connection between the β-hairpin conformational dynamics and how this affects active site catalysis still remains unclear. In this work, we use accelerated molecular dynamics to elucidate the potential interplay between the β-hairpin conformational dynamics and catalytic activity in MAO-N wild type (WT) and its evolved D5 variant. Our study reveals a delicate communication between both MAO-N monomers that impacts the active site architecture, and thus its catalytic efficiency. In both MAO-N WT and the laboratory evolved D5 variant, the β-hairpin conformation in one of the monomers affects the productive binding of the substrate in the active site of the other subunit. However, both MAO-N WT and D5 variants show a quite different behaviour due to the impact of distal mutations introduced experimentally with Directed Evolution on the conformational dynamics of the enzyme