A stochastic attractor participates in chymotrypsin catalysis. A new facet of enzyme catalysis.

The previously observed discrete levels of vibrational parameters of chymotrypsin and tosyl-chymotrypsin were analyzed by the methods of non-linear dynamics in order to investigate their origin. The fractal dimensionality of the step sequence was determined using the correlation function and the Farey-tree method. These methods yielded the same value and indicated the presence of a "Devil's Staircase", i.e. the existence of a stochastic attractor. The latter was assigned to the substrate-mobilizable conformation. The attractor dimension of the catalytic site in the acylated state was found to be indistinguishable from that of the substrate mobilizable conformation. A "Devil's Staircase" signals the transition from the regular to the stochastic regime. This transition is shared by critical phenomena and may be a prerequisite for catalysis.