Kinetic Scheme for Thymidylate Synthase fromEscherichia coli:  Determination from Measurements of Ligand Binding, Primary and Secondary Isotope Effects, and Pre-Steady-State Catalysis†

Biochemistry ◽  
1997 ◽  
Vol 36 (14) ◽  
pp. 4212-4222 ◽  
Author(s):  
H. Trent Spencer ◽  
J. Ernest Villafranca ◽  
James R. Appleman
Keyword(s):  
Steady State ◽  
Ligand Binding ◽  
Thymidylate Synthase ◽  
Isotope Effects ◽  
Kinetic Scheme ◽  
Fromescherichia Coli

Down-regulation of thymidylate synthase expression and its steady-state mRNA by oxaliplatin in colon cancer cells

2004 ◽  
Vol 15 (4) ◽  
pp. 371-376 ◽  
Author(s):  
Kun-Huei Yeh ◽  
Ann-Lii Cheng ◽  
Joeu-Pei Wan ◽  
Chien-Shing Lin ◽  
Chih-Chun Liu
Keyword(s):  
Colon Cancer ◽  
Steady State ◽  
Cancer Cells ◽  
Thymidylate Synthase ◽  
Colon Cancer Cells ◽  
Down Regulation

Steady-state kinetics and isotope effects on the mutant catalytic trimer of aspartate transcarbamoylase containing the replacement of histidine 134 by alanine

Biochemistry ◽  
1992 ◽  
Vol 31 (28) ◽  
pp. 6585-6591 ◽  
Author(s):  
Grover L. Waldrop ◽  
Joanne L. Turnbull ◽  
Laura E. Parmentier ◽  
M. H. O'Leary ◽  
W. W. Cleland ◽  
...  
Keyword(s):  
Steady State ◽  
Isotope Effects ◽  
Aspartate Transcarbamoylase ◽  
Steady State Kinetics

THEORY OF THE TRANSIENT PHASE IN AN ENZYME SYSTEM INVOLVING TWO ENZYME-SUBSTRATE COMPLEXES: THE CASE OF THE FORMATION OF PRODUCTS FROM THE FIRST COMPLEX

1959 ◽  
Vol 37 (4) ◽  
pp. 737-743 ◽  
Author(s):  
Ludovic Ouellet ◽  
James A. Stewart
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Active Site ◽  
Substrate Concentration ◽  
Enzyme System ◽  
Kinetic Scheme ◽  
Enzyme Concentration ◽  
Theoretical Treatment ◽  
Transient Phase ◽  
Enzyme Substrate

A theoretical treatment is worked out for the kinetic scheme[Formula: see text]in which the concentration of P1 is followed. The steady-state and transient phase equations are obtained subject to the condition that the substrate concentration is greatly in excess of the enzyme concentration. The conditions under which evidence in favor of this mechanism can be obtained from experimental data are discussed. Under certain conditions, the weight of the enzyme corresponding to one active site can be determined. Methods for the evaluation of the different constants are described.

Ligand Binding Dynamics to the Heme Domain of the Oxygen Sensor Dos fromEscherichia coli

Biochemistry ◽  
2003 ◽  
Vol 42 (21) ◽  
pp. 6527-6535 ◽  
Author(s):  
Ursula Liebl ◽  
Latifa Bouzhir-Sima ◽  
Laurent Kiger ◽  
Michael C. Marden ◽  
Jean-Christophe Lambry ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Oxygen Sensor ◽  
Fromescherichia Coli ◽  
Heme Domain

scholarly journals Stereochemical Course and Steady State Mechanism of the Reaction Catalyzed by the GDP-fucose Synthetase fromEscherichia coli

1999 ◽  
Vol 274 (38) ◽  
pp. 26743-26750 ◽  
Author(s):  
Saurabh Menon ◽  
Mark Stahl ◽  
Ravindra Kumar ◽  
Guang-Yi Xu ◽  
Francis Sullivan
Keyword(s):  
Steady State ◽  
Fromescherichia Coli ◽  
Mechanism Of The Reaction

scholarly journals Tyr-143 facilitates interdomain electron transfer in flavocytochrome b2

1992 ◽  
Vol 285 (1) ◽  
pp. 187-192 ◽  
Author(s):  
C S Miles ◽  
N Rouvière-Fourmy ◽  
F Lederer ◽  
F S Mathews ◽  
G A Reid ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Isotope Effects ◽  
Mutant Enzyme ◽  
Stopped Flow ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Flavocytochrome B2 ◽  
Rate Determining Step ◽  
Kinetic Isotope

The role of Tyr-143 in the catalytic cycle of flavocytochrome b2 (L-lactate:cytochrome c oxidoreductase) has been examined by replacement of this residue with phenylalanine. The electron-transfer steps in wild-type and mutant flavocytochromes b2 have been investigated by using steady-state and stopped-flow kinetic methods. The most significant effect of the Tyr-143----Phe mutation is a change in the rate-determining step in the reduction of the enzyme. For wild-type enzyme the main rate-determining step is proton abstraction at the C-2 position of lactate, as shown by the 2H kinetic-isotope effect. However, for the mutant enzyme it is clear that the slowest step is interdomain electron transfer between the FMN and haem prosthetic groups. In fact, the rate of haem reduction by lactate, as determined by the stopped-flow method, is decreased by more than 20-fold, from 445 +/- 50 s-1 (25 degrees C, pH 7.5) in the wild-type enzyme to 21 +/- 2 s-1 in the mutant enzyme. Decreases in kinetic-isotope effects seen with [2-2H]lactate for mutant enzyme compared with wild-type, both for flavin reduction (from 8.1 +/- 1.4 to 4.3 +/- 0.8) and for haem reduction (from 6.3 +/- 1.2 to 1.6 +/- 0.5) also provide support for a change in the nature of the rate-determining step. Other kinetic parameters determined by stopped-flow methods and with two external electron acceptors (cytochrome c and ferricyanide) under steady-state conditions are all consistent with this mutation having a dramatic effect on interdomain electron transfer. We conclude that Tyr-143, an active-site residue which lies between the flavodehydrogenase and cytochrome domains of flavocytochrome b2, plays a key role in facilitating electron transfer between FMN and haem groups.

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