Influence of .alpha.-Subunits on the High-Pressure Stability of Apo and Holo .beta.2-Subunits in the Bienzyme Complex Tryptophan Synthase from Escherichia coli

Biochemistry ◽  
1995 ◽  
Vol 34 (6) ◽  
pp. 1959-1967 ◽  
Author(s):  
Susanne Sindern ◽  
Rudi Van Eldik ◽  
Peter Bartholmes
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Tryptophan Synthase ◽  
Alpha Subunits ◽  
Beta 2 ◽  
Pressure Stability

scholarly journals Factors affecting the stereospecificity and catalytic efficiency of the tryptophan synthase-catalysed exchange of the pro-2R and pro-2S protons of glycine

1995 ◽  
Vol 311 (3) ◽  
pp. 1015-1019 ◽  
Author(s):  
J J Milne ◽  
J P G Malthouse
Keyword(s):  
Exchange Reaction ◽  
Catalytic Efficiency ◽  
Second Order ◽  
Beta Subunits ◽  
Enzyme Complex ◽  
Tryptophan Synthase ◽  
Exchange Reactions ◽  
Factors Affecting ◽  
Alpha Subunits ◽  
Beta 2

13C-NMR has been used to follow the tryptophan synthase (EC 4.2.1.20)-catalysed hydrogen-deuterium exchange of the pro-2R and pro-2S protons of [2-13C]glycine. The first- and second-order rate constants for exchange when the alpha 2 beta 2 enzyme complex is or is not saturated with glycine have been determined at pH 7.0 and 7.8. At pH 7.8 the effects of binding the allosteric effector, DL-alpha-glycerol 3-phosphate, and of removing the alpha-subunits have been examined. The beta-subunits preferentially catalyse the exchange of the pro-2R proton of glycine, but adding alpha-subunits decreases the stereospecificity of the exchange reactions. Likewise, binding of DL-alpha-glycerol 3-phosphate to the alpha 2 beta 2 enzyme complex causes a further decrease in the stereospecificity of this reaction. The stereospecificity of the second-order exchange reaction catalysed by the beta-subunits is 136-fold larger than that of the alpha 2 beta 2 enzyme complex in the presence of DL-alpha-glycerol 3-phosphate, while there is only a 5-fold decrease in the stereospecificity of the first-order exchange reaction under the same conditions. We discuss how these results relate to current theories which attempt to explain how the alpha-subunits and DL-alpha-glycerol 3-phosphate modify the catalytic properties of tryptophan synthase.

L-Serine binds to arginine-148 of the .beta.2 subunit of Escherichia coli tryptophan synthase

Biochemistry ◽  
1983 ◽  
Vol 22 (15) ◽  
pp. 3594-3603 ◽  
Author(s):  
Katsuyuki Tanizawa ◽  
Edith Wilson Miles
Keyword(s):  
Escherichia Coli ◽  
Tryptophan Synthase ◽  
Beta 2

scholarly journals Relative activities and stabilities of mutant Escherichia coli tryptophan synthase alpha subunits.

1991 ◽  
Vol 173 (6) ◽  
pp. 1886-1893 ◽  
Author(s):  
W K Lim ◽  
H J Shin ◽  
D L Milton ◽  
J K Hardman
Keyword(s):  
Escherichia Coli ◽  
Tryptophan Synthase ◽  
Alpha Subunits
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