ABSTRACT
Industrial bio-technologists are generally, but not entirely, of the view that flux through a given pathway is usually limited by one step. Such a step is termed the rate-limiting step or the bottleneck with the enzyme catalyzing such a step being referred to as the “pacemaker.” The flux control coefficient is a parameter that describes in quantitative terms the relative contribution of a particular enzyme to flux control in a given pathway. It is not an intrinsic property of the enzyme per se but rather a system property and so is subject to change as the environment changes. Another consequence of the highly branched and intricate nature of cellular metabolism is that the central pathways provide biosynthetic precursors and energy for other pathways. So, as biosynthetic precursors are made, some are fed directly into the biosynthetic routes, which in turn diminish flux through the central metabolic pathways.
