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.

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.

Metabolic Flux

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).

J=Vf-Vr

At equilibrium, there is no flux. Furthermore, it is observed that throughout a steady state pathway, the flux is usually determined by the rate determining step of the reaction.