STEADY-STATE DEPARTURE IN ENZYME REACTIONS

1961 ◽  
Vol 39 (12) ◽  
pp. 2502-2507
Author(s):  
Hyung Kyu Shin ◽  
J. Calvin Giddings
Keyword(s):  
Steady State ◽  
Enzyme Reaction ◽  
Steady State Concentration ◽  
Simple Criterion ◽  
Enzyme Reactions ◽  
State Approximation ◽  
Steady State Approximation ◽  
State Concentration ◽  
General Method

A method is described for calculating the departure from steady-state conditions in enzyme reactions. This provides an immediate and simple criterion for the validity of the steady-state approximation. Several variations of the general method, differing in the degree of simplicity and in the treatment of initial transients, are formulated and discussed. These methods are applied to the general case of an enzyme reaction following the Michaelis–Menten mechanism. Specific applications are made using the data of Chance and Gutfreund. While in these specific cases the steady-state concentration of intermediate is reasonably accurate, the extent of reaction may easily vary from that calculated by means of the steady state.

Theory and practical application of coupled enzyme reactions: one and two auxiliary enzymes

1984 ◽  
Vol 62 (10) ◽  
pp. 945-955 ◽  
Author(s):  
S. P. J. Brooks ◽  
T. Espinola ◽  
C. H. Suelter
Keyword(s):  
Steady State ◽  
Enzyme System ◽  
Enzyme Reaction ◽  
Mathematical Treatment ◽  
Steady State Concentration ◽  
Practical Application ◽  
Enzyme Reactions ◽  
Time Required ◽  
The Cost ◽  
State Concentration

An extended and practical set of equations which describe coupled enzyme reactions is presented. The mathematical treatment relies on two assumptions: (a) the rate of the primary enzyme reaction is constant and (b) the reverse reactions are negligible. The treatment leads to the development of new equations which relate the time required for the concentration of a reaction intermediate to reach a defined fraction of its steady-state concentration to the kinetic parameters of the enzymes when mutarotation of one of the intermediates does not occur. The new equations reduce to those previously derived when the steady-state concentration of the intermediate is small compared with its Km value. A method for minimizing the cost of the two auxiliary enzyme system is also provided.

The total quasi-steady-state approximation for complex enzyme reactions

2008 ◽  
Vol 79 (4) ◽  
pp. 1010-1019 ◽  
Author(s):  
Morten Gram Pedersen ◽  
Alberto M. Bersani ◽  
Enrico Bersani ◽  
Giuliana Cortese
Keyword(s):  
Steady State ◽  
Quasi Steady State ◽  
Enzyme Reactions ◽  
State Approximation ◽  
Steady State Approximation

scholarly journals Studies on the differential equations of enzyme kinetics. I. bimolecular scheme: simplified model

1987 ◽  
Vol 10 (4) ◽  
pp. 797-804
Author(s):  
Claude Marmasse ◽  
Joseph Wiener
Keyword(s):  
Steady State ◽  
Differential Equations ◽  
Enzyme Kinetics ◽  
Differential System ◽  
Integral Curve ◽  
Simplified Model ◽  
State Approximation ◽  
Steady State Approximation ◽  
Rapid Equilibrium ◽  
General Method

The main properties of the solution of the differential system of the model are obtained by qualitative integration. The integral curve is compared with the solutions given by the two classical approximations to the problem: it is shown that the steady-state approximation is to be preferred to the rapid equilibrium theory as a general method and the conditions under which they will furnish accurate results are discussed.

scholarly journals The Total Quasi-Steady-State Approximation for Fully Competitive Enzyme Reactions

2006 ◽  
Vol 69 (1) ◽  
pp. 433-457 ◽  
Author(s):  
Morten Gram Pedersena ◽  
Alberto M. Bersanib ◽  
Enrico Bersanic
Keyword(s):  
Steady State ◽  
Quasi Steady State ◽  
Enzyme Reactions ◽  
State Approximation ◽  
Steady State Approximation

The Quasi-Steady-State Approximation: Numerical Validation

1998 ◽  
Vol 75 (9) ◽  
pp. 1158 ◽  
Author(s):  
Richard A. B. Bond ◽  
Bice S. Martincigh ◽  
Janusz R. Mika ◽  
Reuben H. Simoyi
Keyword(s):  
Steady State ◽  
Quasi Steady State ◽  
Numerical Validation ◽  
State Approximation ◽  
Steady State Approximation

Divergent effects of intravenous GSH and cysteine on renal and hepatic GSH

1992 ◽  
Vol 263 (2) ◽  
pp. R348-R352 ◽  
Author(s):  
S. Aebi ◽  
B. H. Lauterburg
Keyword(s):  
Steady State ◽  
De Novo ◽  
Feedback Inhibition ◽  
Therapeutic Use ◽  
Steady State Concentration ◽  
De Novo Synthesis ◽  
State Concentration ◽  
Cellular Thiol

There is a growing interest in the therapeutic use of sulfhydryls. To assess the effect of glutathione (GSH) and cysteine on the cellular thiol status, thiols were administered intravenously to rats in doses ranging from 1.67 to 8.35 mmol/kg with and without pretreatment with 4 mmol/kg buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis. One hour after administration of 1.67 mmol/kg GSH, the concentration of GSH rose from 5.2 +/- 1.0 to 8.4 +/- 0.9 mumol/g and from 2.5 +/- 0.5 to 3.7 +/- 0.7 mumol/g in liver and kidneys, respectively. After 8.35 mmol/kg, hepatic GSH did not increase further, but renal GSH rose to 6.7 +/- 1.8 mumol/g. Infusion of cysteine increased hepatic GSH to the same extent as intravenous GSH, but renal GSH did not increase after 1.67 mmol/kg and even significantly decreased to 0.6 +/- 0.2 mumol/g after 8.35 mmol/kg. In the presence of BSO, GSH resulted in a significant increase in renal but not hepatic GSH, suggesting that the kidneys take up intact GSH and indicating that the increment in hepatic GSH was due to de novo synthesis. The present data show that hepatic GSH can be markedly increased in vivo by increasing the supply of cysteine. Measurements of hepatic cysteine indicate that up to a concentration of approximately 0.5 mumol/g cysteine is a key determinant of hepatic GSH, such that the physiological steady-state concentration of GSH in the liver appears to be mainly determined by the availability of cysteine. At higher concentrations GSH does not increase further, possibly due to feedback inhibition of GSH synthesis or increased efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

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