[BaileyRadcliffe]

Does any one out there know about enzyme activity?. like the lock and key theory along with the induced - fit theory? :confused:

[medgen]

Um, yes -- but it is quite complicated. I'll try to sum it up this way -- lock and key theory suggested that enzymes worked by producing a binding pocket that had a 3D shape that perfectly fit its substrate. The substrate would bind, all the functional groups required for the reaction would line up perfectly, and voilà -- reaction speeds up.

This has been superseded by the induced fit theory, which has been supported in many ways (the most interesting, IMO, being the antibodies that were raised against transition state analogs -- but that is way too much for here). Induced fit says that the enzyme active site is not optimized for the substrate, but really its transition state. This is the highest energy state for the substrate during the reaction. Basically, the enzyme conformation is slightly stressed when it binds the substrate, and sterically 'pulls' it into its transition state, thereby reducing the free energy level at this point, and speeding up the reaction.

Hope that helps