Enzyme Kinetcis

Question 1

Chymotrypsin

Answer 1

Cleaves peptide bonds of hydrophobic residues
Made in pancreas and activated in duodenum

Question 2

V max

Answer 2

Is the maximum velocity

Question 3

Km michaelis constant

Answer 3

The concentration of substrate at which an enzyme works at half its maximal velocity
It is equal to 1/2v max

Question 4

Low and high km mean

Answer 4

Low km means tight binding of substrate to enzyme
High km means weak binding of susbstrate to enzyme

Question 5

Lineweaver burk plot

Answer 5

Calculates v max where v0 is initial velocity

• Slope = Kₘ/Vmax
• X-intercept = - 1/Kₘ
• Y-intercept = 1/Vmax

Question 6

Competitive inhibition

Answer 6

Increases Kₘ
No effect on v max

Question 7

Non competitive inhibition

Answer 7

No effect on Kₘ
Decreases vmax

Question 8

What does low km mean

Answer 8

High affinity of the enzyme for its substrate

Question 9

Chymotrypsin activity is inhibited by the small molecule indole which binds within the active site of chymotrypsin. What do you think would be the effects of indole upon the parameters KMand Vmaxfor chymotrypsin?

Answer 9

Recall that molecules binding within the active site of an enzyme compete with the substrate for binding to the enzyme. It could therefore be reasonably assumed that indole competes with substrate for binding to chymotrypsin and therefore higher substrate concentrations are needed to obtain a half-maximal velocity. Indole therefore increases KM. In contrast, the maximal velocity (Vmax) will be unaffected.