Reactions for the bistable enzyme-catalysed system proposed by Tyson and Novak.22
X1 represents active Cdh/Apc, X2 inactive Cdh/Apc, X3 inactivating enzymes, X4 activating enzymes, X5 active Cdh/Apc-inactivating-enzyme complexes, X6 inactive Cdh/Apc-activating-enzyme complexes, and X7 the number of CycB-CDK complexes. The first two reactions correspond to enzyme-catalysed inactivation and activation of Cdh/APC. The third reaction corresponds to the dynamics of CycB activity: synthesis at a constant rate, k7, and degradation by natural decay and active Cdh/Apc-induced inactivation.