Many early workers noted that enzymatic activity was associated with proteins, but several scientists (such as Nobel laureate Richard Willstätter) argued that proteins were merely carriers for the true enzymes and that proteins per se were incapable of catalysis.
Mange tidligere forskere havde bemærket, at enzymatisk aktivitet var associeret med proteiner, men flere videnskabsmænd (blandt andre Nobelpristager Richard Willstätter) argumenterede for, at proteiner blot var bærere af de virkelige enzymer, og at proteiner per se var uduelige som katalysatorer.