A model for binary logic in biochemical systems

A model system involving a series of enzyme reactions, some of which display a sigmoid relationship between activity and substrate concentration, is discussed as a possible basis for binary logic in biochemical systems. Under the conditions described, a small change in the concentration of an initial substrate changes the activity of a terminal enzyme from nearly zero to nearly maximal activity, thus approximating a step-function or an on-off switch. Although the mechanistic basis for the sigmoid relationship is not limited to the allosteric model, allosterism is used for purposes of assigning a possible physical meaning to the parameters used in a sample calculation. The possible generation of square wave functions and timed pulses from the model is discussed.