479064-87-4Relevant articles and documents
The bacterial ammonia lyase EncP: A tunable biocatalyst for the synthesis of unnatural amino acids
Weise, Nicholas J.,Parmeggiani, Fabio,Ahmed, Syed T.,Turner, Nicholas J.
supporting information, p. 12977 - 12983 (2015/10/28)
Enzymes of the class I lyase-like family catalyze the asymmetric addition of ammonia to arylacrylates, yielding high value amino acids as products. Recent examples include the use of phenylalanine ammonia lyases (PALs), either alone or as a gateway to deracemization cascades (giving (S)- or (R)-α-phenylalanine derivatives, respectively), and also eukaryotic phenylalanine aminomutases (PAMs) for the synthesis of the (R)-β-products. Herein, we present the investigation of another family member, EncP from Streptomyces maritimus, thereby expanding the biocatalytic toolbox and enabling the production of the missing (S)-β-isomer. EncP was found to convert a range of arylacrylates to a mixture of (S)-α- and (S)-β-arylalanines, with regioselectivity correlating to the strength of electron-withdrawing/-donating groups on the ring of each substrate. The low regioselectivity of the wild-type enzyme was addressed via structure-based rational design to generate three variants with altered preference for either α- or β-products. By examining various biocatalyst/substrate combinations, it was demonstrated that the amination pattern of the reaction could be tuned to achieve selectivities between 99:1 and 1:99 for β:α-product ratios as desired.
Mechanism-inspired engineering of phenylalanine aminomutase for enhanced β-regioselective asymmetric amination of cinnamates
Wu, Bian,Szymanski, Wiktor,Wybenga, Gjalt G.,Heberling, Matthew M.,Bartsch, Sebastian,Dewildeman, Stefaan,Poelarends, Gerrit J.,Feringa, Ben L.,Dijkstra, Bauke W.,Janssen, Dick B.
supporting information; experimental part, p. 482 - 486 (2012/03/22)
Turn to switch: A mutant of phenylalanine aminomutase was engineered that can catalyze the regioselective amination of cinnamate derivatives (see scheme, red) to, for example, β-amino acids. This regioselectivity, along with the X-ray crystal structures, suggests two distinct carboxylate binding modes differentiated by Cβi￡Cipso bond rotation, which determines if β- (see scheme) or α-addition takes place. Copyright
Mechanistic, mutational, and structural evaluation of a taxus phenylalanine aminomutase
Feng, Lei,Wanninayake, Udayanga,Strom, Susan,Geiger, James,Walker, Kevin D.
experimental part, p. 2919 - 2930 (2012/07/14)
The structure of a phenylalanine aminomutase (TcPAM) from Taxus canadensis has been determined at 2.4 A resolution. The active site of the TcPAM contains the signature 4-methylidene-1H-imidazol-5(4H)-one prosthesis, observed in all catalysts of the class I lyase-like family. This catalyst isomerizes (S)-α-phenylalanine to the (R)-β-isomer by exchange of the NH 2/H pair. The stereochemistry of the TcPAM reaction product is opposite of the (S)-β-tyrosine made by the mechanistically related tyrosine aminomutase (SgTAM) from Streptomyces globisporus. Since TcPAM and SgTAM share similar tertiary- and quaternary-structures and have several highly conserved aliphatic residues positioned analogously in their active sites for substrate recognition, the divergent product stereochemistries of these catalysts likely cannot be explained by differences in active site architecture. The active site of the TcPAM structure also is in complex with (E)-cinnamate; the latter functions as both a substrate and an intermediate. To account for the distinct (3R)-β-amino acid stereochemistry catalyzed by TcPAM, the cinnamate skeleton must rotate the C1-Cα and C ipso-β bonds 180° in the active site prior to exchange and rebinding of the NH2/H pair to the cinnamate, an event that is not required for the corresponding acrylate intermediate in the SgTAM reaction. Moreover, the aromatic ring of the intermediate makes only one direct hydrophobic interaction with Leu-104. A L104A mutant of TcPAM demonstrated an ～1.5-fold increase in kcat and a decrease in KM values for sterically demanding 3′-methyl-α-phenylalanine and styryl-α-alanine substrates, compared to the kinetic parameters for TcPAM. These parameters did not change significantly for the mutant with 4′-methyl-α-phenylalanine compared to those for TcPAM.(Figure Presented)
Enhanced conversion of racemic α-arylalanines to (R)-β- arylalanines by coupled racemase/aminomutase catalysis
Cox, Brad M.,Bilsborrow, Joshua B.,Walker, Kevin D.
experimental part, p. 6953 - 6959 (2009/12/25)
(Graph Presented) The Taxus phenylalanine aminomutase (PAM) enzyme converts several (S)-α-arylalanines to their corresponding (R)-β- arylalanines. After incubating various racemic substrateswith 100 μg of PAM for 20 h at 31°C, each (S)-α-arylalanine was enantioselectively isomerized to its corresponding (R)-β-product. With racemic starting materials, the ratio of (R)-β-arylalanine product to the (S)-α-substrate ranged between 0.4 and 1.8, and the remaining nonproductive (R)-α-arylalanine became enriched. To utilize the (R)-α-isomer, the catalysis of a promiscuous alanine racemase from Pseudomonas putida (KT2440) was coupled with that of PAM to increase the production of enantiopure (R)-β-arylalanines from racemic α-arylalanine substrates. The inclusion of a biocatalytic racemization along with the PAM-catalyzed reactionmoderately increased the overall reaction yield of enantiopure β-arylalanines between 4% and 19% (depending on the arylalanine), which corresponded to as much as a 63% increase compared to the turnover with the aminomutase reaction alone. The use of these biocatalysts, in tandem, could potentially find application in the production of chiral β-arylalanine building blocks, particularly, as refinements to the process are made that increase reaction flux, such as by selectively removing the desired (R)-β-arylalanine product from the reaction mixture. 2009 American Chemical Society.
Phenylalanine aminomutase-catalyzed addition of ammonia to substituted cinnamic acids: A route to enantiopure α- and β-amino acids
Szymanski, Wiktor,Wu, Bian,Weiner, Barbara,De Wildeman, Stefaan,Feringa, Ben L.,Janssen, Dick B.
supporting information; experimental part, p. 9152 - 9157 (2010/03/01)
(Chemical Equation Presented) An approach is described for the synthesis of aromatic α- and β-amino acids that uses phenylalanine aminomutase to catalyze a highly enantioselective addition of ammonia to substituted cinnamic acids. The reaction has a broad scope and yields substituted α- and β-phenylalanines with excellent enantiomeric excess. The regioselectivity of the conversion is determined by substituents present at the aromatic ring. A box model for the enzyme active site is proposed, derived from the influence of the hydrophobicity of substituents on the enzyme affinity toward various substrates.
β-styryl- and β-aryl-β-alanine products of phenylalanine aminomutase catalysis
Klettke, Karin L.,Sanyal, Sanjit,Mutatu, Washington,Walker, Kevin D.
, p. 6988 - 6989 (2008/02/06)
The substrate specificity of a Taxus-derived phenylalanine aminomutase (PAM) was investigated, and the enzyme was found to catalyze the conversion of variously substituted vinyl- and aryl-S-∞-alanines to corresponding β-amino acids. This study shows the b
A new route to enantiopure β-aryl-substituted β-amino acids and 4-aryl-substituted β-lactams through lipase-catalyzed enantioselective ring cleavage of β-lactams
Forro, Eniko,Paal, Tihamer,Tasnadi, Gabor,Fueloep, Ferenc
, p. 917 - 923 (2007/10/03)
A simple and efficient direct enzymatic method was developed for the synthesis of 4-aryl-substituted β-lactams and the corresponding β-amino acid enantiomers through the CAL-B (lipase B from Candida antarctica)-catalyzed enantioselective (E > 200) ring cleavage of the corresponding racemic β-lactams with 1 equiv. of H2O in i-Pr2O at 60°C. The product (R)-β-amino acids (ee ≥ 98%, yields ≥ 42%) and unreacted (S)-β-lactams (ee ≥ 95%, yields ≥ 41%) could be easily separated. The ring opening of enantiomeric β-lactams with 18% HCl afforded the corresponding enantiopure β-amino acid hydrochlorides (ee ≥ 99%).
Molecular Basis for the Enantioselective Ring Opening of β-Lactams Catalyzed by Candida antarctica Lipase B
Park, Seongsoon,Forro, Enikoe,Grewal, Harjap,Fueloep, Ferenc,Kazlauskas, Romas J.
, p. 986 - 995 (2007/10/03)
Lipase B from Candida antarctica (CAL-B) catalyzes the slow, but highly enantioselective (E>200), ring-opening alcoholysis of two bicyclic and two 4-aryl-substituted β-lactams. Surprisingly, the rate of the reaction varies with the nature of the alcohols and was fastest with either enantiomer of 2-octanol. A 0.5-g scale reaction with 2-octanol as the nucleophile in diisopropyl ether at 60°C yielded the unreacted β-lactam in 39-46% yield (maximum yield is 50%) with ≥96% ee. The product β-amino acid esters reacted further by polymerization (not isolated or characterized) or by hydrolysis due to small amounts of water in the reaction mixture yielding β-amino acids (7-11% yield, ≥96% ee). The favored enantiomer of all four β-lactams had similar 3-D orientation of substituents, as did most previously reported β-lactams and β-lactones in similar ring-opening reactions. Computer modeling of the ring opening of 4-phenylazetidin-2-one suggests that the reaction proceeds via an unusual substrate-assisted transition state, where the substrate alcohol bridges between the catalytic histidine and the nitrogen of the β-lactam. Computer modeling also suggested that the molecular basis for the high enantioselectivity is a severe steric clash between Ile189 in CAL-B and the phenyl substituent on the slow-reacting enantiomer of the β-lactam.
