Concept #1: Introduction to Covalent Catalysis
Practice: An enzyme has two key catalytic residues, Glu 35 (pKa= 5.9) and Asp 52 (pKa= 4.5). Which of the following is likely true about the mechanism for this enzyme if the optimum pH = 5.2?
Practice: Which of the following mechanisms is not used by enzymes for catalysis?
a) General Acid-base catalysis.
b) Induced fit of enzyme to transition state.
c) Destabilizing the transition state.
d) Providing complementary electrostatics.
e) Binding of metal ions.
f) Specific Acid-Base Catalysis
g) a & c.
h) c & f
i) b, c & f
Practice: Which catalytic mechanism uses an electrophilic cofactor to stabilize a negative charge on an intermediate?
Practice: Which of the following catalytic mechanisms proceeds via noncovalent interactions?
Practice: Suppose that the covalent catalytic mechanism of an enzyme depends on a single active site amino acid (Cys), whose pKa = 8.3. A mutation in a nearby amino acid residue of the enzyme only slightly alters the microenvironment so that the pKa of the Cys residue increases to 10.3. Would this mutation cause the enzyme-catalyzed reaction rate to increase or decrease? Explain.