Chapter 13, Problem 10P

Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book.

Quantitative Relationships Between Rale Constants to Calculate K_m, Kinetic Efficiency (k_cat/K_m) and V_max - II Triose phosphate isomerase catalyzes the conversion of glyceraldehyde-3-phosphate to dihydroxy-acetone phosphate.

$\text{Glyceraldehyde}-\text{3}-\text{P}\rightleftharpoons \text{dihydroxyacetone}-\text{P}$The K_m of this enzyme tor its substrate glyceraldehyde-3-phosphate is 1.8 × 10^-5 M. When [glyceraldehydes-3-phosphate] = 30 μM, the rate of the reaction, v, was 82.5 μmol mL^-1 sec^-1.

a. What is V_max for this enzyme?

b. Assuming 3 nanomoles per mL of enzyme was used in this experiment ([E_total]) = 3 nanomol/mL), what is k_cat for this enzyme?

c. What is the catalytic efficiency (k_cat/K_m) for triose phosphate isomerase?

d. Does the value of k_cat/K_m reveal whether triose phosphate isomerase approaches "catalytic perfection"?

e. What determines the ultimate speed limit of an enzyme-catalyzed reaction? That is, what is it that imposes the physical limit on kinetic perfection?