Structural Determinants of the Stereoinverting Activity of Pseudomonas stutzeri d-Phenylglycine Aminotransferase

Journal Article · Tue Aug 28 00:00:00 EDT 2018 · Biochemistry

DOI:https://doi.org/10.1021/acs.biochem.8b00767· OSTI ID:1476087

Walton, Curtis J. W. ^[1]; Thiebaut, Frédéric ^[1]; Brunzelle, Joseph S. ^[2]; Couture, Jean-François ^[1]; Chica, Roberto A. ^[1]

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1. Univ. of Ottawa, ON (Canada)
2. Northwestern Univ., Argonne, IL (United States)

Aromatic d-amino acids are key precursors for the production of many small molecule therapeutics. Therefore, the development of biocatalytic methods for their synthesis is of great interest. An enzyme that has great potential as a biocatalyst for the synthesis of d-amino acids is the stereoinverting d-phenylglycine aminotransferase (DPAT) from Pseudomonas stutzeri ST-201. This enzyme catalyzes a unique l to d transamination reaction that produces d-phenylglycine and α-ketoglutarate from benzoylformate and l-glutamate, via a mechanism that is poorly understood. Here, we present the crystal structure of DPAT, which shows that the enzyme folds into a two-domain structure representative of class III aminotransferases. Guided by the crystal structure, we performed saturation mutagenesis to probe the substrate binding pockets of the enzyme. Here, these experiments helped us identify two arginine residues (R34 and R407), one in each binding pocket, that are essential to catalysis. Together with kinetic analyses using a library of amino acid substrates, our mutagenesis and structural studies allow us to propose a binding model that explains the dual l/d specificity of DPAT. Our kinetic analyses also demonstrate that DPAT can catalyze the transamination of β- and γ-amino acids, reclassifying this enzyme as an ω-aminotransferase. Collectively, our studies highlight that the DPAT active site is amenable to protein engineering for expansion of its substrate scope, which offers the opportunity to generate new biocatalysts for the synthesis of a variety of valuable optically pure d-amino acids from inexpensive and abundant l-amino acids.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: Canada Foundation for Innovation; Natural Sciences and Engineering Research Council of Canada; Ontario Ministry of Economic Development & Innovation
• OSTI ID: 1476087
• Journal Information: Biochemistry, Journal Name: Biochemistry Journal Issue: 37 Vol. 57; ISSN 0006-2960
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
X-ray crystallography
biocatalysis
crystal structure
enzyme kinetics
enzyme mutation
enzyme structure
genetics
monomers
peptides and proteins
phosphates
structure-function
substrate specificity
surface interactions