Improving the activity and synergistic catalysis of l-aspartate β-decarboxylase by arginine introduction on the surface

Abstract

Decarboxylase typically catalyzes reactions under acidic conditions, which is the drawback for its synergistic catalysis with other enzymes because most enzymes catalyze reactions under near neutral conditions. Improving the activity of decarboxylase under near neutral conditions will greatly contribute to its application in synthetic biology and multienzyme cascade catalysis for the production of chemical compounds, in which many enzymes need to function cooperatively. We choose L-aspartate β-decarboxylase (ASD) that is widely applied in industry to implement the semirational design strategy. The catalytic ability of ASD was successfully improved by substituting glutamic acid for arginine at the 88th position on the surface. The specific activity of an E88R variant was increased to 481 U mg⁻¹ compared to 230 U mg⁻¹ for the wild type. Furthermore, the stability over a range of pH 3.0–8.0 was dramatically increased. The catalytic ability and synergy with other enzymes of the E88R variant were demonstrated in a triple-enzyme system for L-alanine production, and the productivity was increased from 28.2 g (L⁻¹ h⁻¹) to 43.3 g (L⁻¹ h⁻¹). The pH-dependent inactivation of ASD was relieved, and this strategy could be expanded to the decarboxylase family. Additionally, the variant obtained here also shows promising prospects for application in industry.