Mathematical analysis of metabolic networks

Although its important reaction sequences and cycles have been known for more than 25 years, we are still far from a satisfactory theory of intermediary metabolism. The empirical material is overwhelming and increases every year, but the development of a general conception is still in its infancy, although the conceptual progress of recent years has been considerable (for reviews, see [l-3] ). In our opinion, however, the emphasis is too much on static concepts which view the intermediary network as if it were a stock of spare parts, energy and material reserves to be used and filled up by appropriate enzymic reactions. The5 principal bias is towards optimization and control of this supply whereas the dynamic aspects are obviously neglected. There are preferences which testify to this tendency, for example the predominance of the feedback concept, or, in more general terms, of restrictive and repressive control at the metabolic and epigenetic level as a device to meet material demands and to prevent, or to cope with, sudden affluence. Activation and induction are likewise understood to have the same purpose. Indeed, the very concept of ‘con-