... to wild-type(Table 1). Moreover, when the inhibitors could in principleovercome the barrier of the channel constriction and actdirectly in the active site cavity, as in the case of the C435Smutant, ... C435may occur. The series of thiol-reacting agents used to study access of the substrate to the active site of SHC was also found to be auseful tool for studying the possibility of forming anenzyme–inhibitor ... explanations,such as a direct in uence of the inhibitor on the catalyticprocess, may be ruled out since C435 is not involved in the reaction mechanism as shown by the essentially unchangedactivity of the...