Affiliation:
1. Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering Zhejiang University of Technology Hangzhou China
2. Engineering Research Center of Bioconversion and Biopurification of the Ministry of Education Zhejiang University of Technology Hangzhou China
3. The National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals Zhejiang University of Technology Hangzhou China
Abstract
AbstractD‐amino acid oxidase (DAAO)‐catalyzed selective oxidative deamination is a very promising process for synthesizing l‐amino acids including l‐phosphinothricin (l‐PPT, a high‐efficiency and broad‐spectrum herbicide). However, the wild‐type DAAO's low activity toward unnatural substrates like d‐phosphinothricin (d‐PPT) hampers its application. Herein, a DAAO from Caenorhabditis elegans (CeDAAO) was screened and engineered to improve the catalytic potential on d‐PPT. First, we designed a novel growth selection system, taking into account the intricate relationship between the growth of Escherichia coli (E. coli) and the catalytic mechanism of DAAO. The developed system was used for high‐throughput screening of gene libraries, resulting in the discovery of a variant (M6) with significantly increased catalytic activity against d‐PPT. The variant displays different catalytic properties on substrates with varying hydrophobicity and hydrophilicity. Analysis using Alphafold2 modeling and molecular dynamic simulations showed that the reason for the enhanced activity was the substrate‐binding pocket with enlarged size and suitable charge distribution. Further QM/MM calculations revealed that the crucial factor for enhancing activity lies in reducing the initial energy barrier of the reductive half reaction. Finally, a comprehensive binding‐model index to predict the enhanced activity of DAAO toward d‐PPT, and an enzymatic deracemization approach was developed, enabling the efficient synthesis of l‐PPT with remarkable efficiency.