Biology (enzyme)

Enzyme is the key

You should know that enzyme will remain unchanged after the catalytic reaction.

When you use the key to unlock, what will not change at the end? The answer is

clear- The key remains unchanged. Therefore, enzyme is the 'key' in the

hypothesis

key

since enzyme will not change the shape after the reaction

Enzymes are very specific, and it was suggested by Emil Fischer in 1894 that this was because both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.[23] This is often referred to as "the lock and key" model. However, while this model explains enzyme specificity, it fails to explain the stabilization of the transition state that enzymes achieve.


In 1958 Daniel Koshland suggested a modification to the lock and key model: since enzymes are rather flexible structures, the active site is continually reshaped by interactions with the substrate as the substrate interacts with the enzyme.[24] As a result, the substrate does not simply bind to a rigid active site, the amino acid side chains which make up the active site are moulded into the precise positions that enable the enzyme to perform its catalytic function. In some cases, such as glycosidases, the substrate molecule also changes shape slightly as it enters the active site.[25] The active site continues to change until the substrate is completely bound, at which point the final shape and charge is determined.[26

http://en.wikipedia.org/wiki/Image:Induced_fit_diagram.svg