The Key–Lock Theory and the Induced Fit Theory

As a glove changes shape when a hand slips into it , so an enzyme changes its conformation on binding a ligand. This theory of induced fit extends the lock‐and‐key principle that Emil Fischer proposed exactly 100 years ago. The new theory proposed by D. E. Koshland, Jr. in 1958 allows one to explain regulation and cooperative effects, and adds some new specificity principles as well.