The Tryptophan Synthase .alpha.2.beta.2 Complex: Kinetic Studies with a Mutant Enzyme (.beta. K87T) To Provide Evidence for Allosteric Activation by an Aminoacrylate Intermediate

Biochemistry ◽  
1995 ◽  
Vol 34 (39) ◽  
pp. 12704-12711 ◽  
Author(s):  
Utpal Banik ◽  
De-Min Zhu ◽  
P. Boon Chock ◽  
Edith Wilson Miles
Keyword(s):  
Kinetic Studies ◽  
Mutant Enzyme ◽  
Tryptophan Synthase ◽  
Allosteric Activation ◽  
Beta 2

Erythrocyte glutathione synthetase in 5-oxoprolinuria: Kinetic studies of the mutant enzyme and detection of heterozygotes

1976 ◽  
Vol 73 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Agne Larsson ◽  
Rolf Zetterström ◽  
Herje Hörnell ◽  
Ursula Porath
Keyword(s):  
Kinetic Studies ◽  
Mutant Enzyme ◽  
Glutathione Synthetase

scholarly journals Engineering Improves Enzymatic Synthesis of L-Tryptophan by Tryptophan Synthase from Escherichia coli

2020 ◽  
Vol 8 (4) ◽  
pp. 519
Author(s):  
Lisheng Xu ◽  
Fangkai Han ◽  
Zeng Dong ◽  
Zhaojun Wei
Keyword(s):  
Thermal Stability ◽  
Amino Acid ◽  
Directed Evolution ◽  
Amino Acid Residue ◽  
Rational Design ◽  
Molecular Engineering ◽  
Mutant Enzyme ◽  
Tryptophan Synthase ◽  
Mutant Library ◽  
Thermal Stability Of

To improve the thermostability of tryptophan synthase, the molecular modification of tryptophan synthase was carried out by rational molecular engineering. First, B-FITTER software was used to analyze the temperature factor (B-factor) of each amino acid residue in the crystal structure of tryptophan synthase. A key amino acid residue, G395, which adversely affected the thermal stability of the enzyme, was identified, and then, a mutant library was constructed by site-specific saturation mutation. A mutant (G395S) enzyme with significantly improved thermal stability was screened from the saturated mutant library. Error-prone PCR was used to conduct a directed evolution of the mutant enzyme (G395S). Compared with the parent, the mutant enzyme (G395S /A191T) had a Km of 0.21 mM and a catalytic efficiency kcat/Km of 5.38 mM−1∙s−1, which was 4.8 times higher than that of the wild-type strain. The conditions for L-tryptophan synthesis by the mutated enzyme were a L-serine concentration of 50 mmol/L, a reaction temperature of 40 °C, pH of 8, a reaction time of 12 h, and an L-tryptophan yield of 81%. The thermal stability of the enzyme can be improved by using an appropriate rational design strategy to modify the correct site. The catalytic activity of tryptophan synthase was increased by directed evolution.

scholarly journals Directed evolution of the tryptophan synthase β-subunit for stand-alone function recapitulates allosteric activation

2015 ◽  
Vol 112 (47) ◽  
pp. 14599-14604 ◽  
Author(s):  
Andrew R. Buller ◽  
Sabine Brinkmann-Chen ◽  
David K. Romney ◽  
Michael Herger ◽  
Javier Murciano-Calles ◽  
...  
Keyword(s):  
Directed Evolution ◽  
Pyrococcus Furiosus ◽  
Tryptophan Synthase ◽  
Β Subunit ◽  
Allosteric Activation ◽  
Α Subunit ◽  
X Ray ◽  
Catalytic Activities ◽  
Catalytic Potential ◽  
Protein Partners

Enzymes in heteromeric, allosterically regulated complexes catalyze a rich array of chemical reactions. Separating the subunits of such complexes, however, often severely attenuates their catalytic activities, because they can no longer be activated by their protein partners. We used directed evolution to explore allosteric regulation as a source of latent catalytic potential using the β-subunit of tryptophan synthase from Pyrococcus furiosus (PfTrpB). As part of its native αββα complex, TrpB efficiently produces tryptophan and tryptophan analogs; activity drops considerably when it is used as a stand-alone catalyst without the α-subunit. Kinetic, spectroscopic, and X-ray crystallographic data show that this lost activity can be recovered by mutations that reproduce the effects of complexation with the α-subunit. The engineered PfTrpB is a powerful platform for production of Trp analogs and for further directed evolution to expand substrate and reaction scope.

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