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Dick B. Janssen - One of the best experts on this subject based on the ideXlab platform.

  • the sequence and crystal structure of the Alpha Amino Acid ester hydrolase from xanthomonas citri define a new family of beta lactam antibiotic acylases
    Journal of Biological Chemistry, 2003
    Co-Authors: Thomas R M Barends, Jolanda Polderman Tijmes, Cmh Hensgens, Peter A Jekel, Erik De Vries, Dick B. Janssen, Bebauke W Dijkstra
    Abstract:

    Abstract α-Amino Acid ester hydrolases (AEHs) catalyze the hydrolysis and synthesis of esters and amides with an α-Amino group. As such, they can synthesize β-lactam antibiotics from acyl compounds and β-lactam nuclei obtained from the hydrolysis of natural antibiotics. This article describes the gene sequence and the 1.9-A resolution crystal structure of the AEH from Xanthomonas citri. The enzyme consists of an α/β-hydrolase fold domain, a helical cap domain, and a jellyroll β-domain. Structural homology was observed to the Rhodococcus cocaine esterase, indicating that both enzymes belong to the same class of bacterial hydrolases. Docking of a β-lactam antibiotic in the active site explains the substrate specificity, specifically the necessity of an α-Amino group on the substrate, and explains the low specificity toward the β-lactam nucleus.

  • identification of the catalytic residues of Alpha Amino Acid ester hydrolase from acetobacter turbidans by labeling and site directed mutagenesis
    Journal of Biological Chemistry, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Margot C Jeronimusstratingh, Andries P Bruins, Janmetske Van Der Laan, Theo Sonke, Dick B. Janssen
    Abstract:

    Abstract The α-Amino Acid ester hydrolase fromAcetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in β-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl Aminopeptidase. The serine hydrolase inhibitorp-nitrophenyl-p′-guanidino-benzoate appeared to be an active site titrant and was used to label the α-Amino Acid ester hydrolase. Electrospray mass spectrometry and tandem mass spectrometry analysis of peptides from a CNBr digest of the labeled protein showed that Ser205, situated in the consensus sequence, becomes covalently modified by reaction with the inhibitor. Extended sequence analysis showed alignment of this Ser205with the catalytic nucleophile of some α/β-hydrolase fold enzymes, which posses a catalytic triad composed of a nucleophile, an Acid, and a base. Based on the alignments, 10 Amino Acids were selected for site-directed mutagenesis (Arg85, Asp86, Tyr143, Ser156, Ser205, Tyr206, Asp338, His370, Asp509, and His610). Mutation of Ser205, Asp338, or His370 to an alanine almost fully inactivated the enzyme, whereas mutation of the other residues did not seriously affect the enzyme activity. Circular dichroism measurements showed that the inactivation was not caused by drastic changes in the tertiary structure. Therefore, we conclude that the catalytic domain of the α-Amino Acid ester hydrolase has an α/β-hydrolase fold structure with a catalytic triad of Ser205, Asp338, and His370. This distinguishes the α-Amino Acid ester hydrolase from the Ntn-hydrolase family of β-lactam antibiotic acylases.

  • cloning sequence analysis and expression in escherichia coli of the gene encoding an Alpha Amino Acid ester hydrolase from acetobacter turbidans
    Applied and Environmental Microbiology, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Janmetske Van Der Laan, Theo Sonke, Erik J De Vries, Annet E J Van Merode, Rene Floris, Dick B. Janssen
    Abstract:

    The α-Amino Acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing β-lactam antibiotics, such as cephalexin and ampicillin. N-terminal Amino Acid sequencing of the purified α-Amino Acid ester hydrolase allowed cloning and genetic characterization of the corresponding gene from an A. turbidans genomic library. The gene, designated aehA, encodes a polypeptide with a molecular weight of 72,000. Comparison of the determined N-terminal sequence and the deduced Amino Acid sequence indicated the presence of an N-terminal leader sequence of 40 Amino Acids. The aehA gene was subcloned in the pET9 expression plasmid and expressed in Escherichia coli. The recombinant protein was purified and found to be dimeric with subunits of 70 kDa. A sequence similarity search revealed 26% identity with a glutaryl 7-ACA acylase precursor from Bacillus laterosporus, but no homology was found with other known penicillin or cephalosporin acylases. There was some similarity to serine proteases, including the conservation of the active site motif, GXSYXG. Together with database searches, this suggested that the α-Amino Acid ester hydrolase is a β-lactam antibiotic acylase that belongs to a class of hydrolases that is different from the Ntn hydrolase superfamily to which the well-characterized penicillin acylase from E. coli belongs. The α-Amino Acid ester hydrolase of A. turbidans represents a subclass of this new class of β-lactam antibiotic acylases.

Peter A Jekel - One of the best experts on this subject based on the ideXlab platform.

  • the sequence and crystal structure of the Alpha Amino Acid ester hydrolase from xanthomonas citri define a new family of beta lactam antibiotic acylases
    Journal of Biological Chemistry, 2003
    Co-Authors: Thomas R M Barends, Jolanda Polderman Tijmes, Cmh Hensgens, Peter A Jekel, Erik De Vries, Dick B. Janssen, Bebauke W Dijkstra
    Abstract:

    Abstract α-Amino Acid ester hydrolases (AEHs) catalyze the hydrolysis and synthesis of esters and amides with an α-Amino group. As such, they can synthesize β-lactam antibiotics from acyl compounds and β-lactam nuclei obtained from the hydrolysis of natural antibiotics. This article describes the gene sequence and the 1.9-A resolution crystal structure of the AEH from Xanthomonas citri. The enzyme consists of an α/β-hydrolase fold domain, a helical cap domain, and a jellyroll β-domain. Structural homology was observed to the Rhodococcus cocaine esterase, indicating that both enzymes belong to the same class of bacterial hydrolases. Docking of a β-lactam antibiotic in the active site explains the substrate specificity, specifically the necessity of an α-Amino group on the substrate, and explains the low specificity toward the β-lactam nucleus.

  • identification of the catalytic residues of Alpha Amino Acid ester hydrolase from acetobacter turbidans by labeling and site directed mutagenesis
    Journal of Biological Chemistry, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Margot C Jeronimusstratingh, Andries P Bruins, Janmetske Van Der Laan, Theo Sonke, Dick B. Janssen
    Abstract:

    Abstract The α-Amino Acid ester hydrolase fromAcetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in β-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl Aminopeptidase. The serine hydrolase inhibitorp-nitrophenyl-p′-guanidino-benzoate appeared to be an active site titrant and was used to label the α-Amino Acid ester hydrolase. Electrospray mass spectrometry and tandem mass spectrometry analysis of peptides from a CNBr digest of the labeled protein showed that Ser205, situated in the consensus sequence, becomes covalently modified by reaction with the inhibitor. Extended sequence analysis showed alignment of this Ser205with the catalytic nucleophile of some α/β-hydrolase fold enzymes, which posses a catalytic triad composed of a nucleophile, an Acid, and a base. Based on the alignments, 10 Amino Acids were selected for site-directed mutagenesis (Arg85, Asp86, Tyr143, Ser156, Ser205, Tyr206, Asp338, His370, Asp509, and His610). Mutation of Ser205, Asp338, or His370 to an alanine almost fully inactivated the enzyme, whereas mutation of the other residues did not seriously affect the enzyme activity. Circular dichroism measurements showed that the inactivation was not caused by drastic changes in the tertiary structure. Therefore, we conclude that the catalytic domain of the α-Amino Acid ester hydrolase has an α/β-hydrolase fold structure with a catalytic triad of Ser205, Asp338, and His370. This distinguishes the α-Amino Acid ester hydrolase from the Ntn-hydrolase family of β-lactam antibiotic acylases.

  • cloning sequence analysis and expression in escherichia coli of the gene encoding an Alpha Amino Acid ester hydrolase from acetobacter turbidans
    Applied and Environmental Microbiology, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Janmetske Van Der Laan, Theo Sonke, Erik J De Vries, Annet E J Van Merode, Rene Floris, Dick B. Janssen
    Abstract:

    The α-Amino Acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing β-lactam antibiotics, such as cephalexin and ampicillin. N-terminal Amino Acid sequencing of the purified α-Amino Acid ester hydrolase allowed cloning and genetic characterization of the corresponding gene from an A. turbidans genomic library. The gene, designated aehA, encodes a polypeptide with a molecular weight of 72,000. Comparison of the determined N-terminal sequence and the deduced Amino Acid sequence indicated the presence of an N-terminal leader sequence of 40 Amino Acids. The aehA gene was subcloned in the pET9 expression plasmid and expressed in Escherichia coli. The recombinant protein was purified and found to be dimeric with subunits of 70 kDa. A sequence similarity search revealed 26% identity with a glutaryl 7-ACA acylase precursor from Bacillus laterosporus, but no homology was found with other known penicillin or cephalosporin acylases. There was some similarity to serine proteases, including the conservation of the active site motif, GXSYXG. Together with database searches, this suggested that the α-Amino Acid ester hydrolase is a β-lactam antibiotic acylase that belongs to a class of hydrolases that is different from the Ntn hydrolase superfamily to which the well-characterized penicillin acylase from E. coli belongs. The α-Amino Acid ester hydrolase of A. turbidans represents a subclass of this new class of β-lactam antibiotic acylases.

Jolanda J Poldermantijmes - One of the best experts on this subject based on the ideXlab platform.

  • identification of the catalytic residues of Alpha Amino Acid ester hydrolase from acetobacter turbidans by labeling and site directed mutagenesis
    Journal of Biological Chemistry, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Margot C Jeronimusstratingh, Andries P Bruins, Janmetske Van Der Laan, Theo Sonke, Dick B. Janssen
    Abstract:

    Abstract The α-Amino Acid ester hydrolase fromAcetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in β-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl Aminopeptidase. The serine hydrolase inhibitorp-nitrophenyl-p′-guanidino-benzoate appeared to be an active site titrant and was used to label the α-Amino Acid ester hydrolase. Electrospray mass spectrometry and tandem mass spectrometry analysis of peptides from a CNBr digest of the labeled protein showed that Ser205, situated in the consensus sequence, becomes covalently modified by reaction with the inhibitor. Extended sequence analysis showed alignment of this Ser205with the catalytic nucleophile of some α/β-hydrolase fold enzymes, which posses a catalytic triad composed of a nucleophile, an Acid, and a base. Based on the alignments, 10 Amino Acids were selected for site-directed mutagenesis (Arg85, Asp86, Tyr143, Ser156, Ser205, Tyr206, Asp338, His370, Asp509, and His610). Mutation of Ser205, Asp338, or His370 to an alanine almost fully inactivated the enzyme, whereas mutation of the other residues did not seriously affect the enzyme activity. Circular dichroism measurements showed that the inactivation was not caused by drastic changes in the tertiary structure. Therefore, we conclude that the catalytic domain of the α-Amino Acid ester hydrolase has an α/β-hydrolase fold structure with a catalytic triad of Ser205, Asp338, and His370. This distinguishes the α-Amino Acid ester hydrolase from the Ntn-hydrolase family of β-lactam antibiotic acylases.

  • cloning sequence analysis and expression in escherichia coli of the gene encoding an Alpha Amino Acid ester hydrolase from acetobacter turbidans
    Applied and Environmental Microbiology, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Janmetske Van Der Laan, Theo Sonke, Erik J De Vries, Annet E J Van Merode, Rene Floris, Dick B. Janssen
    Abstract:

    The α-Amino Acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing β-lactam antibiotics, such as cephalexin and ampicillin. N-terminal Amino Acid sequencing of the purified α-Amino Acid ester hydrolase allowed cloning and genetic characterization of the corresponding gene from an A. turbidans genomic library. The gene, designated aehA, encodes a polypeptide with a molecular weight of 72,000. Comparison of the determined N-terminal sequence and the deduced Amino Acid sequence indicated the presence of an N-terminal leader sequence of 40 Amino Acids. The aehA gene was subcloned in the pET9 expression plasmid and expressed in Escherichia coli. The recombinant protein was purified and found to be dimeric with subunits of 70 kDa. A sequence similarity search revealed 26% identity with a glutaryl 7-ACA acylase precursor from Bacillus laterosporus, but no homology was found with other known penicillin or cephalosporin acylases. There was some similarity to serine proteases, including the conservation of the active site motif, GXSYXG. Together with database searches, this suggested that the α-Amino Acid ester hydrolase is a β-lactam antibiotic acylase that belongs to a class of hydrolases that is different from the Ntn hydrolase superfamily to which the well-characterized penicillin acylase from E. coli belongs. The α-Amino Acid ester hydrolase of A. turbidans represents a subclass of this new class of β-lactam antibiotic acylases.

Karl Anker Jorgensen - One of the best experts on this subject based on the ideXlab platform.

  • asymmetric 1 4 addition of oxazolones to nitroalkenes by bifunctional cinchona alkaloid thiourea organocatalysts synthesis of α α disubstituted α Amino Acids
    Chemistry: A European Journal, 2008
    Co-Authors: Jose Aleman, Andrea Milelli, Silvia Cabrera, Efraim Reyes, Karl Anker Jorgensen
    Abstract:

    An easy and simple synthetic approach to optically active Alpha,Alpha-quaternary Alpha-Amino Acids using asymmetric organocatalysis is presented. The addition of oxazolones to nitroalkenes catalyzed by thiourea cinchona derivatives provides the corresponding Alpha,Alpha-quaternary Alpha-Amino Acid derivatives with good yields, excellent diastereoselectivities (up to 98 % dr), and from moderate to good enantioselectivities (up to 92 % ee). The reaction can be performed on a large scale. The optically active oxazolone-nitroalkene addition products can be opened in a one-pot reaction to the corresponding ester-amide derivatives. Additional transformations are also presented, such as the synthesis of Amino esters, Amino Acids, and transformation into 3,4-disubstituted pyrrolidin-2-ones.

  • direct catalytic asymmetric mannich reactions of malonates and β keto esters
    Chemistry: A European Journal, 2003
    Co-Authors: Mauro Marigo, Anne Kjaersgaard, Karsten Juhl, Nicholas Gathergood, Karl Anker Jorgensen
    Abstract:

    The first catalytic asymmetric direct Mannich reaction of malonates and beta-keto esters has been developed. Malonates react with an activated N-tosyl-Alpha-imino ester catalyzed by chiral tert-butyl-bisoxazoline/Cu(OTf)(2) to give the Mannich adducts in high yields and with up to 96% ee. These reactions create a chiral quaternary carbon center and it is demonstrated that this new direct Mannich reactions provides for example a new synthetic procedure for the formation of optically active beta-carboxylic ester Alpha-Amino Acid derivatives. A series of different beta-keto esters with various ester substituents has been screened as substrates for the catalytic asymmetric direct Mannich reaction and it was found that the best results in terms of yield, diastereo- and enantioselectivity were obtained when tert-butyl esters of beta-keto esters were used as the substrate. The reaction of different beta-keto tert-butyl esters with the N-tosyl-Alpha-imino ester gave the Mannich adducts in high yields, diastereo- and enantioselectivities (up to 95% ee) in the presence of chiral tert-butyl-bisoxazoline/Cu(OTf)(2) as the catalyst. To expand the synthetic utility of this direct Mannich reaction a diastereoselective decarboxylation reaction was developed for the Mannich adducts leading to a new synthetic approach to attractive optically active beta-keto Alpha-Amino Acid derivatives. Based on the stereochemical outcome of the reactions, various approaches of the N-tosyl-Alpha-imino ester to the chiral bisoxazoline/Cu(II)-substrate intermediate are discussed.

Theo Sonke - One of the best experts on this subject based on the ideXlab platform.

  • identification of the catalytic residues of Alpha Amino Acid ester hydrolase from acetobacter turbidans by labeling and site directed mutagenesis
    Journal of Biological Chemistry, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Margot C Jeronimusstratingh, Andries P Bruins, Janmetske Van Der Laan, Theo Sonke, Dick B. Janssen
    Abstract:

    Abstract The α-Amino Acid ester hydrolase fromAcetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing the side chain peptide bond in β-lactam antibiotics. Data base searches revealed that the enzyme contains an active site serine consensus sequence Gly-X-Ser-Tyr-X-Gly that is also found in X-prolyl dipeptidyl Aminopeptidase. The serine hydrolase inhibitorp-nitrophenyl-p′-guanidino-benzoate appeared to be an active site titrant and was used to label the α-Amino Acid ester hydrolase. Electrospray mass spectrometry and tandem mass spectrometry analysis of peptides from a CNBr digest of the labeled protein showed that Ser205, situated in the consensus sequence, becomes covalently modified by reaction with the inhibitor. Extended sequence analysis showed alignment of this Ser205with the catalytic nucleophile of some α/β-hydrolase fold enzymes, which posses a catalytic triad composed of a nucleophile, an Acid, and a base. Based on the alignments, 10 Amino Acids were selected for site-directed mutagenesis (Arg85, Asp86, Tyr143, Ser156, Ser205, Tyr206, Asp338, His370, Asp509, and His610). Mutation of Ser205, Asp338, or His370 to an alanine almost fully inactivated the enzyme, whereas mutation of the other residues did not seriously affect the enzyme activity. Circular dichroism measurements showed that the inactivation was not caused by drastic changes in the tertiary structure. Therefore, we conclude that the catalytic domain of the α-Amino Acid ester hydrolase has an α/β-hydrolase fold structure with a catalytic triad of Ser205, Asp338, and His370. This distinguishes the α-Amino Acid ester hydrolase from the Ntn-hydrolase family of β-lactam antibiotic acylases.

  • cloning sequence analysis and expression in escherichia coli of the gene encoding an Alpha Amino Acid ester hydrolase from acetobacter turbidans
    Applied and Environmental Microbiology, 2002
    Co-Authors: Jolanda J Poldermantijmes, Peter A Jekel, Janmetske Van Der Laan, Theo Sonke, Erik J De Vries, Annet E J Van Merode, Rene Floris, Dick B. Janssen
    Abstract:

    The α-Amino Acid ester hydrolase from Acetobacter turbidans ATCC 9325 is capable of hydrolyzing and synthesizing β-lactam antibiotics, such as cephalexin and ampicillin. N-terminal Amino Acid sequencing of the purified α-Amino Acid ester hydrolase allowed cloning and genetic characterization of the corresponding gene from an A. turbidans genomic library. The gene, designated aehA, encodes a polypeptide with a molecular weight of 72,000. Comparison of the determined N-terminal sequence and the deduced Amino Acid sequence indicated the presence of an N-terminal leader sequence of 40 Amino Acids. The aehA gene was subcloned in the pET9 expression plasmid and expressed in Escherichia coli. The recombinant protein was purified and found to be dimeric with subunits of 70 kDa. A sequence similarity search revealed 26% identity with a glutaryl 7-ACA acylase precursor from Bacillus laterosporus, but no homology was found with other known penicillin or cephalosporin acylases. There was some similarity to serine proteases, including the conservation of the active site motif, GXSYXG. Together with database searches, this suggested that the α-Amino Acid ester hydrolase is a β-lactam antibiotic acylase that belongs to a class of hydrolases that is different from the Ntn hydrolase superfamily to which the well-characterized penicillin acylase from E. coli belongs. The α-Amino Acid ester hydrolase of A. turbidans represents a subclass of this new class of β-lactam antibiotic acylases.