Sequential enzyme reactions in metabolism and analysis

The development of kinetic schemes for sequences of enzyme reactions contributes to the resolution of two problems. The first of these, the more complex one, concerns the study of the control of metabolic pathways and has been of major interest to biochemists for some time. Two related approaches to the problem have been developed for the interpretation of the behaviour of large assemblies of coupled enzyme reactions. Models can be made which contain the differential equations for the progress of the reactions for all the enzymes of a system. The numerical solutions of this set of equations can be compared with the experimental data for the concentrations of intermediates and their rates of change. Iterative improvements of the model can then be made. Alternatively, if data are only available for a 

The last enzyme serves to remove diphosphoglycerate from an unfavourable equilibrimn. 

Both the above reaction sequences can be monitored by the change in absorbence or fluorescence during the interconversion of NAD and NADH. More recently Webb (1992) developed another continuous spec- 

Other methods for the determination of product dissociation come within the topics of the next section, where the importance of using several approaches to each problem is emphasized. 

A typical example of the use of coupled enzymes for assays of a metabolite concentration is the determination of glucose by the use of the couple hexokinase and glucose-6-phosphate dehydrogenase  

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