Enzyme Residues Flashcards
What is the catalytic triad in chymotrypsin?
Ser195
His57
Asp102 (stabilises +ve His57)
How is the chymotrypsin oxyanion hole formed?
After π-chymotrypsin is cleaved into 3 chains, Ile16 N-terminus on the A chain pairs to Asp194 on the C chain. Res193 and 195 are reoriented to form the side chain
How do aspartyl proteases work?
Deprotonated Asp positions water to attack the scissile bond.
The protonated Asp polarises the carbonyl group of the protein so it is more susceptible to attack
What are the RNas active site residues?
His12
His119
Lys41
What are cysteine protease active site residues?
Cys/His pair
What are the mandelate racemase active site residues?
Lys166 and His297
What features are in the β-keto ACP reducase active site?
Tyr and Lys
Rossman fold and S…YxxxK motif
What are the residues in chymotrypsin specificity pocket?
G266
S189
G216
What are the residues in trypsin specificity pocket?
G266
D189
G216
What are the residues in elastase specificity pocket?
V226
T216
Explain one metal ion mechanisms
Mg2+ takes OH off water
The adjacent phosphate is replaced by a phosphorothioate
Explain two metal ion mechanisms
The Mg2+s stabilize the 2- charge on pentavalent phosphorus
MgI deprotonates a water molecule and helps position the nucleophilic ion generated
MgII interacts with the leaving anion and positions a water molecule for proton donation
What is 3CLpro?
Sars-CoV2 protease which is a cysteine protease that cleaves after Gln
What does aspirin acetylate?
Crucial Ser in the cyclooxygenase component of prostaglandin H2 synthase
How does fluorinating compounds alter the pKa of surrounding groups?
pKa increases
