Exam 2: Chp 14 Flashcards
What are 3 catalytic strategies of enzymes?
1) Covalent
2) Acid-Base
3) Metal ion
How is covalent catalysis performed?
Enzyme forms covalent bond to substrate during reaction
What properties are required for covalent catalysis?
An AA in the active site must be a good nucleophile and good LG later to regenerate the enzyme
What is specific acid/base catalysis?
H+ or OH- diffuses in solution
What is general acid/base catalysis?
H+ or OH- created in transition state via another molecule or group
What is a metalloenzyme?
An enzyme closely associated with a metal ion
How do metal ions facilitate catalysis?
Positively charged electrophiles that stabilize e- density or formal negative charges
What are two examples of a serine protease?
Trypsin and chymotrypsin
What is the function of a protease?
to cleave a peptide bond
What is the function of an esterase?
to cleave an ester bond
What is highly conserved between serine proteases and esterases?
A catalytic triad of Ser, His, and Asp
What can be replaced with what in the catalytic triad of serine proteases and estrerases?
Asp with Glu
Why is His included in the catalytic triad of serine proteases and estrerases?
Have a good pKa for acid base rxns
Why is Ser included in the catalytic triad of serine proteases and estrerases
is a 1° alcohol and functions as nucleophile in reaction
What is the fast step of a chymotrypsin cleavage?
The serine performs nucleophilic attack on substrate’s carbonyl carbon
What is the slow step of a chymotrypsin cleavage?
hydrolysis to release the rest of substrate
How does aspartic protease cleave peptide bonds?
Using 2 aspartic acid residues to cleave between 2 hydrophobic AAs
What is the structure of an aspartic protease?
2 domains that are similar to form a symmetrical protein
Do serine proteases and esterases form a covalent intermediate?
Yes
Do aspartic acid proteases form a covalent intermediate?
No
What kind of catalysis do aspartic proteases employ?
general acid/base catalysis
What kind of protease is HIV protease?
An aspartic protease
Why chorismate mutase unique in the reaction it catalyzes?
The reaction will still occur, just very slow
Why does chromate mutase catalyze formation of prephenate from chorismate?
stabilizes near attack conformation
