Kinetic asymmetry as a key source of functional diversity in biochemical networks

From the analysis of the dynamic properties of various symmetric and asymme tric kinetic schemes, the present report demonstrates that all kinetic sche mes, which can be hypothetically divided into two equal halves about an axi s of mirror symmetry, are endowed with structural metastability under mass- closed conditions. In mass-closed symmetric schemes, absolute symmetry in r eaction conditions in two halves is essential for the occurrence of ordered dynamic behaviour. Even an infinitesimal deviation from the symmetry relat ions instantaneously drives such systems from limit-cycles to turbulence. R eaction schemes with no axes of symmetry may exhibit a large variety of com plex, structurally stable temporal order for wide ranges of values of syste m parameters and variables. Kinetic asymmetry, therefore, may confer to bio chemical networks the functional diversity as well as stability against env ironmental perturbations. (C) 1999 Elsevier Science B.V. All rights reserve d.