Flux (metabolism)

Flux, or metabolic flux is the rate of turnover of molecules through a metabolic pathway. Flux is regulated by the enzymes involved in a pathway. Within cells, regulation of flux is vital for all metabolic pathways to regulate the pathway's activity under different conditions. Flux is therefore of great interest in metabolic network modelling, where it is analysed via flux balance analysis and metabolic control analysis. In this manner, flux is the movement of matter through metabolic networks that are connected by metabolites and cofactors, and is therefore a way of describing the activity of the metabolic network as a whole using a single characteristic. It is easiest to describe the flux of metabolites through a pathway by considering the reaction steps individually. The flux of the metabolites through each reaction (J) is the rate of the forward reaction (Vf), less that of the reverse reaction (Vr): At equilibrium, there is no flux. Furthermore, it is observed that throughout a steady-state pathway, the flux is determined to varying degrees by all steps in the pathway. The degree of influence is measured by the flux control coefficient. Control of flux through a metabolic pathway requires that The degree to which metabolic steps determine the metabolic flux varies based on the organisms' metabolic needs. The change in flux that occurs due to the above requirement being communicated to the rest of the metabolic pathway in order to maintain a steady-state. Control of flux in a metabolic pathways: The control of flux is a systemic property, that is it depends, to varying degrees, on all interactions in the system. The control of flux is measured by the flux control coefficient In a linear chain of reactions, the flux control coefficient will have values between zero and one. A step with a flux control coefficient of zero means that, that particular step, has no influence over the steady-state flux. A step in a linear chain with a flux control coefficient of one means that that particular step has complete control over the steady-state flux.