Effect of channeling on reaction cascades with competing reactions.

(a) Product formation velocity of the nonchanneled system, vnon, decreases as the degradation or consumption rate of intermediates, kdeg, increases. (b) Reaction velocity of the nonchanneled system falls off for increasing ‘degree of reversibility’ of the first reaction in the cascade, . In this case the reaction is in lieu of Eq (1a). In both plots vnon is compared to the velocity of the channeled system, vch. The concentrations of enzymes and enzyme-enzyme complexes are equal in both systems on both panels, i.e. [Ei] = [E1] = [E2] = [E12]; in panel (b) the ratio vnon/vch is independent of [Ei]. Substrate concentration [S] = 90 nM, the degree of diffusion control is γ1 = γch = 1 (see Eq (10)), and the rate constants are the same as in Fig 1. Thin dotted line denotes vch = vnon.