Drug Metabolism in Drug Design and Development Basic Concepts and Practice

S

(μM)

0

5

10

15

20

25

(nmol/min/mg protein)V
70 60 50 40 30 20 10 0

V/S

(ml/min/mg protein)

0 10203040
(pmol/min/mg protein)V
70 60 50 40 30 20 10 0

E2

E1

1

/S

(1/μM)

-20246

0.25 0.20 0.15 0.10 (1/pmol/min/mg protein)0.051/V 0.00 -0.05

E1

E2

(a)

(b)

(c)

FIGURE 13.3

Determination of the potential involvements of multiple enzymes in a biotransformation pathway using the common

biochemical plots. As shown by the plots, (

a) Michaelis–Menten plot; (

b) Eadie–Hofstee plot; and (

c) Lineweaver–Burk plot, at least two

enzymatic components (E1 and E2) are responsible for the substrate’s biotransformation: one high affinity and low capacity, and the other lowaffinity and high capacity. Of the three plots shown, the Eadie–Hofstee plot most apparently demonstrates the biphasic kinetics due to eithermultiple enzymes or possibly the deviations from Michaelis–Menten kinetics, that is, homotropic cooperation.

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