Question

The KM value of chymotrypsin is 29.1 x 10-3 M with the peptide GYA as a substrate. The initial rate measured at a substrate concentration of 0.05 M was 2.5 x 10-3 M. Calculate the initial rates at 0.01 M and 0,1 M. How would you expect KM to change as the temperature of the system increases?

Answer 1

. Step 1: Calculate Vmax using MM equation from the available data.

Michaelis- Menten Equation max I Km IS Where, Vmax = Maximum rate of catalysis at saturating [S] VoRate of catalysis at specified [S] Km= MM Constant [S] = substrate concetration Eqn 1 Given, Vo0.0025 M/s Km = 0.0291 M S0.05 M Putting the values in equation1 Vo (Km[S]) msws-Loom 0.0025 M/s 0.0291+ 0.05 M 0MM Vmax 0.05 M Hence, Vmax3.96E-03 M/s

# Step 2: Use Vmax from above step to calculate Vo values-

Michaelis- Menten Equation Vmax [S] -Eqn 1 Km [S] Where, Vmax Maximum rate of catalysis at saturating [S] VoRate of catalysis at specified [S] KmMM Constant SSubstrate concetration Vo -Eqn 1 Given, Vmax 0.0037 M/s Km0.0291 M S0.01 M Putting the values in equation 1 Or, vo- 0.0037 M/s 0.0100 M 0.0391 M Vo 9.44E-04 mM/s

Michaelis- Menten Equation Vmax [S] KmS] Where, Vmax = Maximum rate of catalysis at saturating [S] VoRate of catalysis at specified [S] Given, Vmax = 0.0037 M/S Km0.0291 M Km= MM Constant IS0.10 M [S]Substrate concetration Putting the values in equation1 Or, 0.0037 M/s 0.1000 M 0.1291 M Vo= Or, Vo2.86E-03 mM/s

Km decrease with increase in temperature till the attainment of optimum temperature because increase in temperature increases collision frequency among the enzyme and substrate molecules.