Crystal Structures and Catalytic Mechanism of l-erythro-3,5-Diaminohexanoate Dehydrogenase and Rational Engineering for Asymmetric Synthesis of β-Amino Acids

Angew Chem Int Ed Engl. 2021 Apr 26;60(18):10203-10210. doi: 10.1002/anie.202017225. Epub 2021 Mar 24.

Abstract

Amino acid dehydrogenases (AADHs) have shown considerable potential as biocatalysts in the asymmetric synthesis of chiral amino acids. However, compared to the widely studied α-AADHs, limited knowledge is available about β-AADHs that enable the synthesis of β-amino acids. Herein, we report the crystal structures of a l-erythro-3,5-diaminohexanoate dehydrogenase and its variants, the only known member of β-AADH family. Crystal structure analysis, site-directed mutagenesis studies and quantum chemical calculations revealed the differences in the substrate binding and catalytic mechanism from α-AADHs. A number of rationally engineered variants were then obtained with improved activity (by 110-800 times) toward various aliphatic β-amino acids without an enantioselectivity trade-off. Two β-amino acids were prepared by using the outstanding variants with excellent enantioselectivity (>99 % ee) and high isolated yields (86-87 %). These results provide important insights into the molecular mechanism of 3,5-DAHDH, and establish a solid foundation for further design of β-AADHs for the asymmetric synthesis of β-amino acids.

Keywords: asymmetric synthesis; biocatalysis; catalytic mechanism; protein engineering; β-amino acid dehydrogenase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Oxidoreductases / chemistry
  • Amino Acid Oxidoreductases / metabolism*
  • Amino Acids / biosynthesis*
  • Amino Acids / chemistry
  • Biocatalysis
  • Crystallography, X-Ray
  • Models, Molecular
  • Molecular Structure
  • Mycoplasma / enzymology*
  • Protein Engineering*

Substances

  • Amino Acids
  • Amino Acid Oxidoreductases
  • L-erythro-3,5-diaminohexanoate dehydrogenase