Lock-and-key model

a model used to suggest the mode of operation of an enzyme in which the substrate fits into the active site of the protein like a key into a lock

Description
Advanced understanding of the activation and action of many enzymes (and antibody-antigen interactions) shows the lock-and-key model of substrate recognition to be only one of several applicable (and not mutually exclusive) models, with models of induced fit and conformational selection in the interaction between enzyme and substrate often more closely resembling experimental observation.