Enzyme Mechanisms

What are proteases?

enzymes that hydrolyze (break) peptide bonds

What do proteases do to the ½ life of proteins?

shorten it to milliseconds

What does the stability of proteins come from?

peptide bond

How does the peptide bond give stability?

partial double bond character lowers electrophilicity of carbonyl carbon

What are two examples of serine proteases?

trypsin and chymotrypsin

What three strategies do serine proteases use to catalyze peptide bond hydrolysis?

Activate a nucleophile, increase carbonyl electrophilicity, and stabilize the tetrahedral intermediate

What do serine proteases require?

an active site serine residue for covalent catalysis

What residues does chymotrypsin cleave after?

Aromatic amino acids (Phe, Tyr, Trp)

What residues does trypsin cleave after?

Lys and Arg

What residues does elastase cleave after?

Small neutral amino acids (Gly, Ala, Val, Ser)

What is Thrombin?

Serine Protease in blood clotting cascade

What is Plasmin?

Serine Protease essential to dissolve blood clots

What is Acetyl-cholinesterase?

Serine esterasee