Lecture 12 - Enzymatic catalysis Flashcards
Enzymes are good catalysts due to their
specificity of substrate binding and optimal arrangement of catalytic groups
Enzymatic catalytic mechanisms are divided into what six classes?
- Acid-base catalysis
- Covalent catalysis
- Metal ion catalysis
- Electrostatic catalysis
- Proximity and orientation effects
- Preferential binding of the transition state complex
General acid catalysis involves
partial proton transfer from a Brønsted acid
General base catalysis involves
partial proton abstraction from a Brønsted base
RNase A is a digestive enzyme that functions to
hydrolyze RNA to individual nucleotides
RNase A contains what two important residues?
His 12 and His 119
In RNase A, what acts as the general base?
His 12
In RNase A, what acts as the general acid?
His 119
In covalent catalysis, reaction rates are accelerated through
the transient formation of a catalyst-substrate covalent bond
In covalent catalysis, the covalent bond is usually formed by the reaction of a nucleophilic group on the ______ with an electrophilic group on the ______
catalyst; substrate
A good covalent catalyst must combine the properties of
high nucleophilicity and the ability to form a good leaving group
Groups with ________ make good covalent catalysts
highly mobile electrons
Which amino acids make good covalent catalysts?
- Histidine
- Cysteine
- Aspartate
- Serine
Serine proteases are a class of
proteolytic enzymes in which a serine hydroxyl plays an essential role in catalysis
In chymotrypsin, the oxygen of the serine side chain
attacks the carbonyl group of the peptide
