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what common strategies do enzymes employ to catalyze specific reactions?
- 1. Covalent catalysis
- 2. general acid base catalysis
- 3. Metal ion catalysis
- 4. Catalysis by approximation and orientation
what is covalent catalysis
in covalent catalysis, the active site contains a reactive group, usually a powerful nucleophile that becomes temporarily covalently modified in the course of catalysis. The proteolytic enyme chymotrypsin provides an excellent example of this mechanism
what is general acid-base catalysis
in general acid-base catalysis, a molecule other than water plays the role of a proton donor or acceptor. Chymotrypsin uses a histidine residue as a base catalyst to enhance the nucleophilic power of the serine
what is metal ion catalysis
metal ions can function catalytically in several ways. For instance, a metal ion may serve as an electrophilic catalyst, stabilizing a negative charge on a reaction intermediate. Alternatively, a metal ion may generate a nucleophile by increasing hte acidity of a nearby moleculem such s water. Finally, a metal ion may bind to the substrate increasing the number of interactions with the enzyme and thus the binding energy. Metal ions are required cofactors for many of the nezymes that we will encounter in our study of biochemistry
what is catalysis by approximation and orientation?
many reactions include two distinct substrates. in such cases, the reaction rate may be considerably enhanced by bringing the two substrates into proximity and in the proper oritentation on a signle binding surface of an enzyme
what are the three types of reversible inhibition?
competitive, non-competitive, and uncompetitive
How does suicide inhibition work?
a suicide inhibitor is a chemically modified substrate. The inhibitor binds to the enzyme as a substrate and is initially processed by the normal catalytic mechanism. The mechanism of catalysis then generates a chemically reactive intermediate that inactivates the enzyme through covalent modification.
What does penicillin and aspirin have in common?
they are both irreversible inhibitors