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β‐Aminopeptidase‐Catalyzed Biotransformations of β 2 ‐Dipeptides: Kinetic Resolution and Enzymatic Coupling
Author(s) -
Heck Tobias,
Reimer Artur,
Seebach Dieter,
Gardiner James,
Deniau Gildas,
Lukaszuk Aneta,
Kohler HansPeter E.,
Geueke Birgit
Publication year - 2010
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.200900757
Subject(s) - chemistry , diastereomer , hydrolysis , peptide , amino acid , stereochemistry , enantioselective synthesis , substrate (aquarium) , catalysis , kinetic resolution , biocatalysis , peptide synthesis , enzyme catalysis , aminopeptidase , enzyme , organic chemistry , reaction mechanism , leucine , biochemistry , oceanography , geology
We have previously shown that the β‐aminopeptidases BapA from Sphingosinicella xenopeptidilytica and DmpA from Ochrobactrum anthropi can catalyze reactions with non‐natural β 3 ‐peptides and β 3 ‐amino acid amides. Here we report that these exceptional enzymes are also able to utilize synthetic dipeptides with N‐terminal β 2 ‐amino acid residues as substrates under aqueous conditions. The suitability of a β 2 ‐peptide as a substrate for BapA or DmpA was strongly dependent on the size of the C α substituent of the N‐terminal β 2 ‐amino acid. BapA was shown to convert a diastereomeric mixture of the β 2 ‐peptide H‐β 2 hPhe‐β 2 hAla‐OH, but did not act on diastereomerically pure β 2 ,β 3 ‐dipeptides containing an N‐terminal β 2 ‐homoalanine. In contrast, DmpA was only active with the latter dipeptides as substrates. BapA‐catalyzed transformation of the diastereomeric mixture of H‐β 2 hPhe‐β 2 hAla‐OH proceeded along two highly S ‐enantioselective reaction routes, one leading to substrate hydrolysis and the other to the synthesis of coupling products. The synthetic route predominated even at neutral pH. A rise in pH of three log units shifted the synthesis‐to‐hydrolysis ratio ( v S / v H ) further towards peptide formation. Because the equilibrium of the reaction lies on the side of hydrolysis, prolonged incubation resulted in the cleavage of all peptides that carried an N‐terminal β‐amino acid of S configuration. After completion of the enzymatic reaction, only the S enantiomer of β 2 ‐homophenylalanine was detected ( ee >99 % for H‐( S )‐β 2 ‐hPhe‐OH, E >500); this confirmed the high enantioselectivity of the reaction. Our findings suggest interesting new applications of the enzymes BapA and DmpA for the production of enantiopure β 2 ‐amino acids and the enantioselective coupling of N‐terminal β 2 ‐amino acids to peptides.