Biochemistry

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6. Enzymes and Enzyme Kinetics

Covalent Catalysis

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Covalent Catalysis

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Problem

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?

3
Problem

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

4
Problem

Which catalytic mechanism uses an electrophilic cofactor to stabilize a negative charge on an intermediate?

5
Problem

Which of the following catalytic mechanisms proceeds via noncovalent interactions?

6
Problem

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.