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Teruhiko Beppu - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the Tryptophanase expression in Symbiobacterium thermophilum in a coculture with Geobacillus stearothermophilus
Applied Microbiology and Biotechnology, 2014Co-Authors: Tomo-o Watsuji, Tomoya Yamabe, Satoshi Tamazawa, Hiroka Ikemura, Takanori Ohishi, Tohyo Matsuda, Hatsumi Shiratori-takano, Hideaki Takano, Teruhiko Beppu, Kenji UedaAbstract:The Tryptophanase-positive Symbiobacterium thermophilum is a free-living syntrophic bacterium that grows effectively in a coculture with Geobacillus stearothermophilus. Our studies have shown that S. thermophilum growth depends on the high CO2 and low O2 condition established by the precedent growth of G. stearothermophilus. The use of an anoxic atmosphere containing high CO2 allows S. thermophilum to grow independently of G. stearothermophilus, but the cellular yield is ten times lower than that achieved in the coculture. In this study, we characterized the coculture-dependent expression and activity of Tryptophanase in S. thermophilum. S. thermophilum cells accumulated a marked amount of indole in a coculture with G. stearothermophilus, but not in the bacterium’s pure culture irrespective of the addition of tryptophan. S. thermophilum cells accumulated indole in its pure culture consisting of conditioned medium (medium supplied with culture supernatant of G. stearothermophilus). Proteomic analysis identified the protein specifically produced in the S. thermophilum cells grown in conditioned medium, which was a Tryptophanase encoded by tna2 (STH439). An attempt to isolate the Tryptophanase-inducing component from the culture supernatant of G. stearothermophilus was unsuccessful, but we did discover that the indole accumulation occurs when 10 mM bicarbonate is added to the medium. RT-PCR analysis showed that the addition of bicarbonate stimulated transcription of tna2. The transcriptional start site, identified within the tna2 promoter, was preceded by the −24 and −12 consensus sequences specified by an alternative sigma factor, σ54. The evidence suggests that the transcription of some genes involved in amino acid metabolism is σ54-dependent, and that a bacterial enhancer-binding protein containing a PAS domain controls the transcription under the presence of high levels of bicarbonate.
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Cloning, nucleotide sequence, and overexpression in Escherichia coli of the β-tyrosinase gene from an obligately symbiotic thermophile, Symbiobacterium thermophilum
Applied Microbiology and Biotechnology, 1993Co-Authors: Toshikatsu Hirahara, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum is an obligately symbiotic thermophile that can grow only in coculture with a specific Bacillus strain. The amino acid sequences of fragments obtained by cyanogen bromide decomposition of the thermostable β-tyrosinase (tyrosine phenol-lyase, E.C. 4.1.99.2) from this organism resembled that of the Tryptophanase produced by the same organism. DNA-probing with the Tryptophanase gene as the hybridization probe led to cloning in Escherichia coli of the β-tyrosinase ( tpl ) gene. The nucleotide sequence revealed that the β-tyrosinase of 458 amino acids (relative molecular mass, 52269) showed significant similarity in amino acid sequence to the Tryptophanase over the entire sequence. DNA manipulation of the cloned tpl gene in E. coli led to production of 375 times as much β-tyrosinase as that produced by the original S. thermophilum strain.
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cloning nucleotide sequences and overexpression in escherichia coli of tandem copies of a Tryptophanase gene in an obligately symbiotic thermophile symbiobacterium thermophilum
Applied and Environmental Microbiology, 1992Co-Authors: Toshikatsu Hirahara, S Suzuki, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum, a thermophilic bacterium, is a thermostable Tryptophanase producer that can grow only in coculture with a specific Bacillus strain. Two thermostable Tryptophanase genes, tna-1 and tna-2, that are located close to each other were cloned into Escherichia coli from S. thermophilum by the DNA-probing method. The nucleotide and deduced amino acid sequences indicate that Tna1 and Tna2 share 92% identical amino acids in a total of 453 amino acids. By means of DNA manipulation with E. coli host-vector systems, Tna1 and Tna2 were produced in very large amounts in enzymatically active forms. Comparison of the NH2-terminal amino acid sequences and the enzymatic properties of the Tryptophanases purified from the original S. thermophilum strain and these two Tryptophanases from recombinant E. coli cells suggest that in S. thermophilum, only Tna2 is produced and tna-1 is silent. Notwithstanding the great similarity in amino acid sequence between Tna1 and Tna2, the two enzymes differ markedly in activation energy for catalysis and thermostability.
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purification and properties of thermostable Tryptophanase from an obligately symbiotic thermophile symbiobactevium thermophilum
Agricultural and biological chemistry, 1991Co-Authors: Seibun Suzuki, Sueharu Horinouchi, Toshikatsu Hirahara, Teruhiko BeppuAbstract:A thermostable Tryptophanase was extracted from a thermophilic bacterium, Symbiobacterium thermophilum strain T, which is obligately symbiotic with the thermophilic Bacillus strain S. The enzyme was purified 21-fold to homogeneity with 19% recovery by a series of chromatographies using anion-exchange, hydroxylapatite, hydrophobic interaction, and MonoQ anion-exchange columns. The molecular weight of the purified enzyme was estimated to be approximately 210,000 by gel filtration, while the molecular weight of its subunit was 46,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which indicates that the native enzyme is composed of four homologous subunits. The isoelectric point of the enzyme was 4.9. The Tryptophanase was stable to heating at 65°C for 20 min and the optimum temperature for the enzyme activity for 20 min reaction was 70°C. The optimum PH was 7.0. The NH2-terminal amino acid sequence of this Tryptophanase shows similarity to that of Escherichia coli K-12, despite a great diffe...
Toshikatsu Hirahara - One of the best experts on this subject based on the ideXlab platform.
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Cloning, nucleotide sequence, and overexpression in Escherichia coli of the β-tyrosinase gene from an obligately symbiotic thermophile, Symbiobacterium thermophilum
Applied Microbiology and Biotechnology, 1993Co-Authors: Toshikatsu Hirahara, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum is an obligately symbiotic thermophile that can grow only in coculture with a specific Bacillus strain. The amino acid sequences of fragments obtained by cyanogen bromide decomposition of the thermostable β-tyrosinase (tyrosine phenol-lyase, E.C. 4.1.99.2) from this organism resembled that of the Tryptophanase produced by the same organism. DNA-probing with the Tryptophanase gene as the hybridization probe led to cloning in Escherichia coli of the β-tyrosinase ( tpl ) gene. The nucleotide sequence revealed that the β-tyrosinase of 458 amino acids (relative molecular mass, 52269) showed significant similarity in amino acid sequence to the Tryptophanase over the entire sequence. DNA manipulation of the cloned tpl gene in E. coli led to production of 375 times as much β-tyrosinase as that produced by the original S. thermophilum strain.
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cloning nucleotide sequences and overexpression in escherichia coli of tandem copies of a Tryptophanase gene in an obligately symbiotic thermophile symbiobacterium thermophilum
Applied and Environmental Microbiology, 1992Co-Authors: Toshikatsu Hirahara, S Suzuki, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum, a thermophilic bacterium, is a thermostable Tryptophanase producer that can grow only in coculture with a specific Bacillus strain. Two thermostable Tryptophanase genes, tna-1 and tna-2, that are located close to each other were cloned into Escherichia coli from S. thermophilum by the DNA-probing method. The nucleotide and deduced amino acid sequences indicate that Tna1 and Tna2 share 92% identical amino acids in a total of 453 amino acids. By means of DNA manipulation with E. coli host-vector systems, Tna1 and Tna2 were produced in very large amounts in enzymatically active forms. Comparison of the NH2-terminal amino acid sequences and the enzymatic properties of the Tryptophanases purified from the original S. thermophilum strain and these two Tryptophanases from recombinant E. coli cells suggest that in S. thermophilum, only Tna2 is produced and tna-1 is silent. Notwithstanding the great similarity in amino acid sequence between Tna1 and Tna2, the two enzymes differ markedly in activation energy for catalysis and thermostability.
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purification and properties of thermostable Tryptophanase from an obligately symbiotic thermophile symbiobactevium thermophilum
Agricultural and biological chemistry, 1991Co-Authors: Seibun Suzuki, Sueharu Horinouchi, Toshikatsu Hirahara, Teruhiko BeppuAbstract:A thermostable Tryptophanase was extracted from a thermophilic bacterium, Symbiobacterium thermophilum strain T, which is obligately symbiotic with the thermophilic Bacillus strain S. The enzyme was purified 21-fold to homogeneity with 19% recovery by a series of chromatographies using anion-exchange, hydroxylapatite, hydrophobic interaction, and MonoQ anion-exchange columns. The molecular weight of the purified enzyme was estimated to be approximately 210,000 by gel filtration, while the molecular weight of its subunit was 46,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which indicates that the native enzyme is composed of four homologous subunits. The isoelectric point of the enzyme was 4.9. The Tryptophanase was stable to heating at 65°C for 20 min and the optimum temperature for the enzyme activity for 20 min reaction was 70°C. The optimum PH was 7.0. The NH2-terminal amino acid sequence of this Tryptophanase shows similarity to that of Escherichia coli K-12, despite a great diffe...
Akihiko Shimada - One of the best experts on this subject based on the ideXlab platform.
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Flexible Enantioselectivity of Tryptophanase Attributable to Benzene Ring in Heterocyclic Moiety of D-Tryptophan
Life, 2012Co-Authors: Akihiko Shimada, Haruka OzakiAbstract:The invariance principle of enzyme enantioselectivity must be absolute because it is absolutely essential to the homochiral biological world. Most enzymes are strictly enantioselective, and Tryptophanase is one of the enzymes with extreme absolute enantioselectivity for L-tryptophan. Contrary to conventional knowledge about the principle, Tryptophanase becomes flexible to catalyze D-tryptophan in the presence of diammonium hydrogenphosphate. Since D-amino acids are ordinarily inert or function as inhibitors even though they are bound to the active site, the inhibition behavior of D-tryptophan and several inhibitors involved in this process was examined in terms of kinetics to explain the reason for this flexible enantioselectivity in the presence of diammonium hydrogenphosphate. Diammonium hydrogenphosphate gave Tryptophanase a small conformational change so that D-tryptophan could work as a substrate. As opposed to other D-amino acids, D-tryptophan is a very bulky amino acid with a benzene ring in its heterocyclic moiety, and so we suggest that this structural feature makes the catalysis of D-tryptophan degradation possible, consequently leading to the flexible enantioselectivity. The present results not only help to understand the mechanism of enzyme enantioselectivity, but also shed light on the origin of homochirality.
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reaction pathway of Tryptophanase catalyzed l tryptophan synthesis from d serine
Journal of Chromatography B, 2011Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Abstract Tryptophanase, l -tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While Tryptophanase is not inert to d -serine in the absence of diammonium hydrogenphosphate, it can undergo l -tryptophan synthesis from d -serine along with indole in the presence of it. It has been well known that Tryptophanase synthesizes l -tryptophan from l -serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l -tryptophan synthesis from d -serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d -serine. The salt gives Tryptophanase a small conformational change, which makes it possible to catalyze d -serine. Tryptophanase-bound d -serine produces l -tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality.
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Reaction pathway of Tryptophanase-catalyzed l-tryptophan synthesis from d-serine
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences, 2011Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Tryptophanase, l-tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While Tryptophanase is not inert to d-serine in the absence of diammonium hydrogenphosphate, it can undergo l-tryptophan synthesis from d-serine along with indole in the presence of it. It has been well known that Tryptophanase synthesizes l-tryptophan from l-serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l-tryptophan synthesis from d-serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d-serine. The salt gives Tryptophanase a small conformational change, which makes it possible to catalyze d-serine. Tryptophanase-bound d-serine produces l-tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality. © 2011 Elsevier B.V.
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Tryptophanase catalyzed l tryptophan synthesis from d serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute stereospecificity for optically active stereoisomers, catalyzes the synthesis of L-tryptophan from L-serine and indole through a β-substitution mechanism of the ping-pong type, and has no activity on D-serine. We previously reported that Tryptophanase changed its stereospecificity to degrade D- tryptophan in highly concentrated diammonium hydrogen phosphate, (NH4)2HPO4 solution. The present study provided the same stereospecific change seen in the D- tryptophan degradation reaction also occurs in tryptophan synthesis from D-serine. Tryptophanase became active to D-serine to synthesize L-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. D-serine seems to undergo β-replacement via an enzyme-bonded α-aminoacylate intermediate to yield L-tryptophan.
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Tryptophanase-catalyzed L-tryptophan synthesis from D-serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute stereospecificity for optically active stereoisomers, catalyzes the synthesis of l-tryptophan from l-serine and indole through a beta-substitution mechanism of the ping-pong type, and has no activity on d-serine. We previously reported that Tryptophanase changed its stereospecificity to degrade d-tryptophan in highly concentrated diammonium hydrogen phosphate, (NH(4))(2)HPO(4) solution. The present study provided the same stereospecific change seen in the d-tryptophan degradation reaction also occurs in tryptophan synthesis from d-serine. Tryptophanase became active to d-serine to synthesize l-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. d-serine seems to undergo beta-replacement via an enzyme-bonded alpha-aminoacylate intermediate to yield l-tryptophan.
Sueharu Horinouchi - One of the best experts on this subject based on the ideXlab platform.
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Cloning, nucleotide sequence, and overexpression in Escherichia coli of the β-tyrosinase gene from an obligately symbiotic thermophile, Symbiobacterium thermophilum
Applied Microbiology and Biotechnology, 1993Co-Authors: Toshikatsu Hirahara, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum is an obligately symbiotic thermophile that can grow only in coculture with a specific Bacillus strain. The amino acid sequences of fragments obtained by cyanogen bromide decomposition of the thermostable β-tyrosinase (tyrosine phenol-lyase, E.C. 4.1.99.2) from this organism resembled that of the Tryptophanase produced by the same organism. DNA-probing with the Tryptophanase gene as the hybridization probe led to cloning in Escherichia coli of the β-tyrosinase ( tpl ) gene. The nucleotide sequence revealed that the β-tyrosinase of 458 amino acids (relative molecular mass, 52269) showed significant similarity in amino acid sequence to the Tryptophanase over the entire sequence. DNA manipulation of the cloned tpl gene in E. coli led to production of 375 times as much β-tyrosinase as that produced by the original S. thermophilum strain.
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cloning nucleotide sequences and overexpression in escherichia coli of tandem copies of a Tryptophanase gene in an obligately symbiotic thermophile symbiobacterium thermophilum
Applied and Environmental Microbiology, 1992Co-Authors: Toshikatsu Hirahara, S Suzuki, Sueharu Horinouchi, Teruhiko BeppuAbstract:Symbiobacterium thermophilum, a thermophilic bacterium, is a thermostable Tryptophanase producer that can grow only in coculture with a specific Bacillus strain. Two thermostable Tryptophanase genes, tna-1 and tna-2, that are located close to each other were cloned into Escherichia coli from S. thermophilum by the DNA-probing method. The nucleotide and deduced amino acid sequences indicate that Tna1 and Tna2 share 92% identical amino acids in a total of 453 amino acids. By means of DNA manipulation with E. coli host-vector systems, Tna1 and Tna2 were produced in very large amounts in enzymatically active forms. Comparison of the NH2-terminal amino acid sequences and the enzymatic properties of the Tryptophanases purified from the original S. thermophilum strain and these two Tryptophanases from recombinant E. coli cells suggest that in S. thermophilum, only Tna2 is produced and tna-1 is silent. Notwithstanding the great similarity in amino acid sequence between Tna1 and Tna2, the two enzymes differ markedly in activation energy for catalysis and thermostability.
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purification and properties of thermostable Tryptophanase from an obligately symbiotic thermophile symbiobactevium thermophilum
Agricultural and biological chemistry, 1991Co-Authors: Seibun Suzuki, Sueharu Horinouchi, Toshikatsu Hirahara, Teruhiko BeppuAbstract:A thermostable Tryptophanase was extracted from a thermophilic bacterium, Symbiobacterium thermophilum strain T, which is obligately symbiotic with the thermophilic Bacillus strain S. The enzyme was purified 21-fold to homogeneity with 19% recovery by a series of chromatographies using anion-exchange, hydroxylapatite, hydrophobic interaction, and MonoQ anion-exchange columns. The molecular weight of the purified enzyme was estimated to be approximately 210,000 by gel filtration, while the molecular weight of its subunit was 46,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which indicates that the native enzyme is composed of four homologous subunits. The isoelectric point of the enzyme was 4.9. The Tryptophanase was stable to heating at 65°C for 20 min and the optimum temperature for the enzyme activity for 20 min reaction was 70°C. The optimum PH was 7.0. The NH2-terminal amino acid sequence of this Tryptophanase shows similarity to that of Escherichia coli K-12, despite a great diffe...
Takeshi Saito - One of the best experts on this subject based on the ideXlab platform.
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reaction pathway of Tryptophanase catalyzed l tryptophan synthesis from d serine
Journal of Chromatography B, 2011Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Abstract Tryptophanase, l -tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While Tryptophanase is not inert to d -serine in the absence of diammonium hydrogenphosphate, it can undergo l -tryptophan synthesis from d -serine along with indole in the presence of it. It has been well known that Tryptophanase synthesizes l -tryptophan from l -serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l -tryptophan synthesis from d -serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d -serine. The salt gives Tryptophanase a small conformational change, which makes it possible to catalyze d -serine. Tryptophanase-bound d -serine produces l -tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality.
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Reaction pathway of Tryptophanase-catalyzed l-tryptophan synthesis from d-serine
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences, 2011Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Noriko FujiiAbstract:Tryptophanase, l-tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While Tryptophanase is not inert to d-serine in the absence of diammonium hydrogenphosphate, it can undergo l-tryptophan synthesis from d-serine along with indole in the presence of it. It has been well known that Tryptophanase synthesizes l-tryptophan from l-serine through a β-substitution mechanism of the ping-pong type. However, a metabolic pathway of l-tryptophan synthesis from d-serine has remained unclear. The present study aims to elucidate it. Diammonium hydrogenphosphate plays a role in the emergence of catalytic activity on d-serine. The salt gives Tryptophanase a small conformational change, which makes it possible to catalyze d-serine. Tryptophanase-bound d-serine produces l-tryptophan synthesis by β-replacement reaction via the enzyme-bound aminoacrylate intermediate. Our result will be valuable in studying the origin of homochirality. © 2011 Elsevier B.V.
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Tryptophanase catalyzed l tryptophan synthesis from d serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute stereospecificity for optically active stereoisomers, catalyzes the synthesis of L-tryptophan from L-serine and indole through a β-substitution mechanism of the ping-pong type, and has no activity on D-serine. We previously reported that Tryptophanase changed its stereospecificity to degrade D- tryptophan in highly concentrated diammonium hydrogen phosphate, (NH4)2HPO4 solution. The present study provided the same stereospecific change seen in the D- tryptophan degradation reaction also occurs in tryptophan synthesis from D-serine. Tryptophanase became active to D-serine to synthesize L-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. D-serine seems to undergo β-replacement via an enzyme-bonded α-aminoacylate intermediate to yield L-tryptophan.
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Tryptophanase-catalyzed L-tryptophan synthesis from D-serine in the presence of diammonium hydrogen phosphate
International Journal of Molecular Sciences, 2009Co-Authors: Akihiko Shimada, Haruka Ozaki, Takeshi Saito, Fujii NorikoAbstract:Tryptophanase, an enzyme with extreme absolute stereospecificity for optically active stereoisomers, catalyzes the synthesis of l-tryptophan from l-serine and indole through a beta-substitution mechanism of the ping-pong type, and has no activity on d-serine. We previously reported that Tryptophanase changed its stereospecificity to degrade d-tryptophan in highly concentrated diammonium hydrogen phosphate, (NH(4))(2)HPO(4) solution. The present study provided the same stereospecific change seen in the d-tryptophan degradation reaction also occurs in tryptophan synthesis from d-serine. Tryptophanase became active to d-serine to synthesize l-tryptophan in the presence of diammonium hydrogen phosphate. This reaction has never been reported before. d-serine seems to undergo beta-replacement via an enzyme-bonded alpha-aminoacylate intermediate to yield l-tryptophan.
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Tryptophanase Activity on D-Tryptophan
Progress in Biological Chirality, 2004Co-Authors: Akihiko Shimada, Noriko Fujii, Takeshi SaitoAbstract:Tryptophanase is an enzyme with very strict stereospecificity, cleaving L-tryptophan but not D-tryptophan. The chapter discusses the flexibility of enzyme stereospecificity; also, an attempt is made to change the stereospecificity. The Tryptophanase activity toward D-tryptophan in the presence of ammonium phosphate is also demonstrated. Circular dichroism (CD) and florescence spectroscopy are used to monitor the conformational changes inducing activity toward D-tryptophan in ammonium phosphate solution. Tryptophanase is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the hydrolytic P-elimination of L-tryptophan (L-Trp) to indole and ammonium pyruvate, consisting of four identical 52 kDa monomers. Each monomer contains one molecule of PLP, which forms an aldimine bond with a lysine residue. TPase is one of the enzymes with the highest stereospecificity for optical isomers. It has long been believed that Tryptophanase is absolutely inactive to D-tryptophan (D-Trp). The presence of PLP, DAP, TAP, and high temperatures are key factors in enhancing activity toward D-Trp by inducing subtle, but vital changes to bring TPase in closer contact with D-Trp. TPase activity toward D-Trp reaches 20% of its activity toward L-Trp when TPase reacts with D-Trp under optimal conditions. The reaction system discussed in the chapter is appropriate to further investigate the mechanisms behind TPase stereospecificity. The clarification of this mechanism can help in solving the problems associated with the homochiral origins in early metabolism. The result of this study indicates that TPase stereospecificity may be artificially changed. © 2004 Elsevier Ltd All rights reserved.
