Book contents
- Frontmatter
- Contents
- Preface
- Part One Basic steady state enzyme kinetics
- 1 Derivation of a rate equation
- 2 A closer look at the basic assumptions
- 3 Enzyme inhibition
- 4 Reversible enzyme-catalyzed reactions
- Part Two Enzyme reaction sequence
- Part Three Non-hyperbolic enzyme kinetics
- Part Four Control of multi-enzyme systems
- Part Five Solutions To problems
- Author index
- Subject index
4 - Reversible enzyme-catalyzed reactions
Published online by Cambridge University Press: 23 November 2009
- Frontmatter
- Contents
- Preface
- Part One Basic steady state enzyme kinetics
- 1 Derivation of a rate equation
- 2 A closer look at the basic assumptions
- 3 Enzyme inhibition
- 4 Reversible enzyme-catalyzed reactions
- Part Two Enzyme reaction sequence
- Part Three Non-hyperbolic enzyme kinetics
- Part Four Control of multi-enzyme systems
- Part Five Solutions To problems
- Author index
- Subject index
Summary
The derivation of eq. (1.18), a rate equation for an enzyme-catalyzed reaction, was possible because a number of assumptions were stipulated. These assumptions were expressed in eqs. (1.12) through (1.15). The first three of these assumptions are mandatory, and they have been discussed in some detail in chapters 1 and 2. The fourth assumption, namely (P) = 0, was imposed as a matter of convenience, and it is not an absolute requirement. The thrust of the present chapter will be to investigate the kinetic behavior of an enzyme-catalyzed reaction when the restriction (P) has been removed.
Derivation of a rate equation by matrix inversion
A model for such a reaction is shown in Figure 4.1. There is a logical problem with the sequence shown in Figure 4.1. As the reaction proceeds from left to right, the enzyme combines with the substrate to form an enzyme-substrate complex which can either dissociate to enzyme plus substrate or be converted to enzyme plus product. However, when the reaction proceeds from right to left, the model shows that the enzyme combines with the product to form an enzyme-substrate complex instantaneously. Figure 4.2 presents a sequence which seems more logical. Whether or not the reaction sequences shown in Figure 4.1 and Figure 4.2 are distinct on the basis of steady state kinetics, the latter sequence is more acceptable logically. Yet, the question still arises, “Might the reaction sequence involve even more intermediate binary complexes?” If so, would this affect the steady state behavior of the enzyme? One way to approach this problem is to derive the steady state rate equation for the reaction sequence in Figure 4.2, and then set the product concentration equal to zero and see how that equation compares to eq. (1.21), which was obtained for the reaction sequence in Figure 1.1.
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- Chapter
- Information
- Enzyme KineticsFrom Diastase to Multi-enzyme Systems, pp. 44 - 56Publisher: Cambridge University PressPrint publication year: 1994
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