Lock and key theory was given by Emil Fischer. The main reason behind the introduction of this theory was to let people make aware of the function of the enzymes. Like the key fits in to the lock so same is the case with the enzymes as well. In the enzymes case the enzymes fits in the substrate and then the functioning and its mechanism begins.
The model along with the theory was given in 1894. The model had been a successful one and hence it began to be taught in schools as well. In many schools and even for the biologist students this topic became an interesting and a beneficial one. The enzymes and substrate model is also known as the lock and key model as well.
Later on this model began to be of less importance for people as it was not much accurate and then the model named as induced fit model came in to being and then this model was replaced by that one. The reaction between the enzymes and its other half named as substrate can be speed up due to an increase in temperature.
Through the increase in temperature the enzymes function properly and then as a result they began to produce the by product effectively and efficiently. In this model the enzymes plays the role of lock and the role of key is played by substrate. At the end of the reaction enzymes stays the same and hence it can be used at any time and can also be used for a longer time period.
As enzymes can be used again so same is the case with the lock too. The enzymes is the only best suitable structure for substrate as it is well specified with the lock and key functioning, so hence as a result this means that enzymes catalyse the substrate.