On the mechanism of ribonuclease action.

All the suggestions that have been made for the mechanism of action of ribonuclease can be classified into one or another of two classes, depending on the geometry of the displacement in the first step. Studies of related model compounds indicate that one of these two classes should include as a part of the mechanism a pentacoordinate intermediate, which undergoes pseudorotation before product can be formed. It is unlikely that the pseudorotation would be rate-limiting in the reaction of the normal substrate.