Metabolism sequence interaction

Metabolic chemistry is characterized by functionality. Each reaction is important because of its participation in a sequence of reactions, and each sequence interacts functionally with other sequences. 

Metabolic sequences must interact in a very wide variety of ways. Two types seem likely to be of special importance to metabolic regulation (1) interaction between R sequences (with positive coupling coefficients) and U sequences (with negative coefficients) of the type illustrated by Fig. 1, and (2) competition between sequences, either for a branch-point metabolite or for ATP. 

Many other multisubstrate examples abound in metabolism. In effect, these situations are managed by realizing that the interaction of the enzyme with its many substrates can be treated as a series of uni- or bisubstrate steps in a multi-step reaction pathway. Thus, the complex mechanism of a multisubstrate reaction is resolved into a sequence of steps, each of which obeys the single- and double-displacement patterns just discussed. 

As we have seen, carcinogenesis is a prolonged multi-stage process which usually occurs over many years. Because of its complexity there are, in principle, many critical steps at which food-related substances or metabolic processes may interact with the sequence of events so as to accelerate, delay or even reverse it. Diet-related anti-carcinogenesis can usefully be classified into ... 

This system displays a two-enzyme kinetic model in which bioconversion is controlled by the interaction between the two reactions and the mass transfer. This situation offers a more realistic model for the conditions occurring in vivo, in which some pathways of intermediary metabolism consist of linear sequences of reactions. These pathways take place in highly organized compartments. 

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