title: Expanding the threonine aldolase toolbox for the asymmetric synthesis of tertiary α-amino acids.
abstract: The direct biochemical synthesis of tertiary α-amino acids with a wide range of diversity was recently reported using natural threonine aldolases LTA from Aeromonas jandei and DTA from Pseudomonas sp. Here, we describe the identification of five novel threonine aldolases which accept alanine and serine as amino acid donors. The enzymes were found by sequence database analysis using known aldolases as template. All enzymes were overexpressed in Escherichia coli and purified, and their biochemical properties were characterized. The new enantiocomplementary L- and D-threonine aldolases catalyze the asymmetric synthesis of β-hydroxy α-methyl- and α-hydroxymethyl-α-amino acids with good conversion and perfect enantioselectivity at α-carbon of the products (e.e. >99 %). The structural basis for the broad donor specificity of these threonine aldolases is analyzed based on crystal structure alignments and amino acid sequences comparison.
authors.affiliation: Institute of Organic Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010, Graz, Austria. kateryna.lypetska@tugraz.at.
authors.forename: Kateryna
authors.initials: K
authors.lastname: Fesko
authors.affiliation: Institute of Organic Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010, Graz, Austria.|Austrian Centre of Industrial Biotechnology (ACIB) GmbH, Petersgasse 14, 8010, Graz, Austria.
authors.forename: Gernot A
authors.initials: GA
authors.lastname: Strohmeier
authors.affiliation: Institute of Organic Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010, Graz, Austria.|Austrian Centre of Industrial Biotechnology (ACIB) GmbH, Petersgasse 14, 8010, Graz, Austria.
authors.forename: Rolf
authors.initials: R
authors.lastname: Breinbauer
mesh_terms: D000333:Aeromonas / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000096:biosynthesis*; D003001:Cloning, Molecular; D019295:Computational Biology / Q000379:methods; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D012696:Glycine Hydroxymethyltransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation; D011549:Pseudomonas / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D012696:Glycine Hydroxymethyltransferase
keywords: Aldol reactions; Biocatalysis; Enzyme catalysis; Tertiary amino acids; Threonine aldolase