(a) At what substrate concentration would an enzyme with a kcat of 30.0 s −1 and a Km of XXXXXXXXXXM operate at one-quarter of its maximum rate? (b) Determine the fraction of Vmax that would be...

(a) At what substrate concentration would an enzyme with a kcat of 30.0
s
−1 and a Km of 0.0050 M operate at one-quarter of its maximum rate?
(b) Determine the fraction of Vmax
that would be obtained at the following substratecon centrations [S]: ½Km, 2Km, and 10Km.
(c) An enzyme that catalyzes the reaction X ⇌ Y is isolated from two bacterial species.
The enzymes have the same Vmax but different Km values for the substrate X. Enzyme A has a Km of 2.0 μM, and enzyme B has a Km of 0.5 μM. The plot below shows the kinetics of reactions carried out with the same concentration of each enzyme and with [X] = 1 μM. Which curve corresponds to which enzyme?