Sources for structure formation and switches in metabolic pathways

Zonation of function, i.e. localization of metabolic activity in certain regions of histologically uniform tissues, is an often observed phenomenon. Moreover, experiments show that such metabolic patterns are highly dynamical. Since in the pathways of intermediary metabolism no autocatalytic reactions are observed, different types of metabolic regulation are sources of the non-linearities necessary for structure formation. Two models of biochemical reactions frequently encountered in metabolic pathways, namely a bisubstrate kinetics model with substrate inhibition, and an allosteric model with product regulation, are presented. It is shown, that they are well-suited to reproduce the dynamical behavior suggested by experimental findings, like their capability to act as switches, or their ability for spatiotemporal pattern formation in mature tissues.