scholarly journals Steady-state and presteady-state kinetics of the H+/hexose cotransporter (STP1) from Arabidopsis thaliana expressed in Xenopus oocytes.

1994 ◽  
Vol 269 (32) ◽  
pp. 20417-20424
Author(s):  
K.J. Boorer ◽  
D.D. Loo ◽  
E.M. Wright
Keyword(s):  
Arabidopsis Thaliana ◽  
Steady State ◽  
Xenopus Oocytes ◽  
Kinetics Of ◽  
Presteady State Kinetics

Presteady-state kinetics of Bacillus 1,3–1,4-β-glucanase: binding and hydrolysis of a 4-methylumbelliferyl trisaccharide substrate

2001 ◽  
Vol 357 (1) ◽  
pp. 195-202
Author(s):  
Mireia ABEL ◽  
Antoni PLANAS ◽  
Ulla CHRISTENSEN
Keyword(s):  
Steady State ◽  
Rate Constant ◽  
Product Formation ◽  
Lag Phase ◽  
Wild Type ◽  
Induced Fit ◽  
Enzyme Substrate ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Presteady State Kinetics

In the present study the first stopped-flow experiments performed on Bacillus 1,3–1,4-β-glucanases are reported. The presteady-state kinetics of the binding of 4-methylumbelliferyl 3-O-β-cellobiosyl-β-d-glucoside to the inactive mutant E134A, and the wild-type-catalysed hydrolysis of the same substrate, were studied by measuring changes in the fluorescence of bound substrate or 4-methylumbelliferone produced. The presteady-state traces all showed an initial lag phase followed by a fast monoexponential phase leading to equilibration (for binding to E134A) or to steady state product formation (for the wild-type reaction). The lag phase, with a rate constant of the order of 100s−1, was independent of the substrate concentration; apparently an induced-fit mechanism governs the formation of enzyme–substrate complexes. The concentration dependencies of the observed rate constant of the second presteady-state phase were analysed according to a number of reaction models. For the reaction of the wild-type enzyme, it is shown that the fast product formation observed before steady state is not due to a rate-determining deglycosylation step. A model that can explain the observed results involves, in addition to the induced fit, a conformational change of the productive ES complex into a form that binds a second substrate molecule in a non-productive mode.

Kinetics of Rubisco Activation as Determined from Gas-exchange Measurements in Antisense Plants of Arabidopsis thaliana Containing Reduced Levels of Rubisco Activase

1997 ◽  
Vol 24 (6) ◽  
pp. 811 ◽  
Author(s):  
Keith A. Mott ◽  
Gordon W. Snyder ◽  
Ian E. Woodrow
Keyword(s):  
Arabidopsis Thaliana ◽  
Steady State ◽  
Gas Exchange ◽  
Rubisco Activase ◽  
Activation Rate ◽  
Time Courses ◽  
Activation Rates ◽  
Kinetics Of ◽  
Rubisco Activation ◽  
Intercellular Co2

The kinetics of the increase in photosynthesis rate following an increase in PFD were determined in wildtype Arabidopsis thaliana plants and in two antisense plants that contained reduced levels of Rubisco activase. Experiments were conducted over a range of intercellular CO2 mole fractions (ci). The rate at which photosynthesis approached steady-state following an increase in PFD was similar for wildtype and transformed plants at low values of ci. At higher values of ci, however, wildtype plants approached steady state more rapidly than did the antisense plants. Photosynthesis time courses were used to calculate Rubisco activation rates for the three types of plants, and Rubisco activation rate was found to be proportional to activase content at a ci of 280 µmol mol-1. These data are discussed in the context of proposed mechanisms for Rubisco activase in the activation of Rubisco.

scholarly journals Temperature Dependence of Steady-State and Presteady-State Kinetics of a Type IIb Na+/Pi Cotransporter

2007 ◽  
Vol 215 (2-3) ◽  
pp. 81-92 ◽  
Author(s):  
Andrea Bacconi ◽  
Silvia Ravera ◽  
Leila V. Virkki ◽  
Heini Murer ◽  
Ian C. Forster
Keyword(s):  
Steady State ◽  
Temperature Dependence ◽  
Kinetics Of ◽  
Presteady State Kinetics

Kinetic analysis of mechanism of intestinal Na+-dependent sugar transport

1985 ◽  
Vol 248 (5) ◽  
pp. C498-C509 ◽  
Author(s):  
D. Restrepo ◽  
G. A. Kimmich
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Sugar Transport ◽  
Enzyme Kinetic ◽  
Steady State Distribution ◽  
State Distribution ◽  
Least Squares Fit ◽  
Coupling Stoichiometry ◽  
Rate Limiting ◽  
Kinetics Of

Zero-trans kinetics of Na+-sugar cotransport were investigated. Sugar influx was measured at various sodium and sugar concentrations in K+-loaded cells treated with rotenone and valinomycin. Sugar influx follows Michaelis-Menten kinetics as a function of sugar concentration but not as a function of Na+ concentration. Nine models with 1:1 or 2:1 sodium:sugar stoichiometry were considered. The flux equations for these models were solved assuming steady-state distribution of carrier forms and that translocation across the membrane is rate limiting. Classical enzyme kinetic methods and a least-squares fit of flux equations to the experimental data were used to assess the fit of the different models. Four models can be discarded on this basis. Of the remaining models, we discard two on the basis of the trans sodium dependence and the coupling stoichiometry [G. A. Kimmich and J. Randles, Am. J. Physiol. 247 (Cell Physiol. 16): C74-C82, 1984]. The remaining models are terter ordered mechanisms with sodium debinding first at the trans side. If transfer across the membrane is rate limiting, the binding order can be determined to be sodium:sugar:sodium.

Sign in / Sign up

Export Citation Format

Share Document