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The conventional enzyme-substrate interaction scheme invokes Fischer’s lock and key type affinity or Koshland’s induced fit theory. That is, a substrate is identified by the enzyme by virtue of a topographical complementation, and thereafter, the enzyme-substrate complex undergoes a "transition-state," leading to products. [7]
The side-chain theory (German, Seitenkettentheorie) is a theory proposed by Paul Ehrlich (1854–1915) to explain the immune response in living cells. Ehrlich theorized from very early in his career that chemical structure could be used to explain why the immune response occurred in reaction to infection .
Daniel Koshland's theory of enzyme-substrate binding is that the active site and the binding portion of the substrate are not exactly complementary. [10] The induced fit model is a development of the lock-and-key model and assumes that an active site is flexible and changes shape until the substrate is completely bound.
Enzyme kinetics is the investigation of how enzymes bind substrates and turn them into products. [67] The rate data used in kinetic analyses are commonly obtained from enzyme assays. In 1913 Leonor Michaelis and Maud Leonora Menten proposed a quantitative theory of enzyme kinetics, which is referred to as Michaelis–Menten kinetics. [68]
As shown on the right, enzymes with a substituted-enzyme mechanism can exist in two states, E and a chemically modified form of the enzyme E*; this modified enzyme is known as an intermediate. In such mechanisms, substrate A binds, changes the enzyme to E* by, for example, transferring a chemical group to the active site, and is then released.
Using the "lock and key model" of enzyme binding, a drug (key) must be of roughly the proper dimensions to fit the enzyme's binding site (lock). [28] Using the appropriately sized molecular scaffold, drugs must also interact with the enzyme non-covalently in order to maximize binding affinity binding constant and reduce the ability of the drug ...
An illustration to show (a) Alberty-Hammes-Eigen model, and (b) Chou's model, where E denotes the enzyme whose active site is colored in red, while the substrate S in blue. The theory of diffusion-controlled reaction was originally utilized by R.A. Alberty, Gordon Hammes, and Manfred Eigen to estimate the upper limit of enzyme-substrate reaction.
A decade before Michaelis and Menten, Victor Henri found that enzyme reactions could be explained by assuming a binding interaction between the enzyme and the substrate. [11] His work was taken up by Michaelis and Menten, who investigated the kinetics of invertase, an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose. [12]