BIOINORGANIC CHEMISTRY A Short Course Second Edition

46 BIOCHEMISTRY FUNDAMENTALS

111

V

K

VV

= m

()+

max []S max

(2.3)

Plotting 1/ V vs. 1/[ S ], one obtains a straight line having a slope of Km / Vmax with
ay - axis intercept of 1/ Vmax and an x - intercept of − 1/ Km as shown in Figure
2.13. Lineweaver – Burk plots of enzyme activity in the presence of an inhibitor
can distinguish the type of inhibitor. Competitive inhibitors have a molecular
structure similar to that of the substrate and will alterKm but not Vmax because
they compete with the substrate for binding at the enzyme ’ s active site but do
not change the enzyme ’ s affi nity for substrate. Noncompetitive inhibitors bear
no structural similarity to the substrate but bind the free enzyme or enzyme –
substrate complex at a site other than the active site. They reduce the enzyme ’ s

Figure 2.12 Graphical representation of the Michaelis – Menten equation for nonal-
losteric enzymes.

Vmax

1/2 Vmax

Km

first order region

zero order region

[S] increases

Initial Reaction Rate

Figure 2.13 Lineweaver – Burk plot for no inhibitor, competitive inhibition, and non-
competitive inhibition.

Km

Vmax

slope =

1

1

1

Vmax

1

Km

• competitive
  inhibitor

1

Km

• no inhibitor
  or
  noncompetitive
  inhibitor

1

Vmax

noncompetitive

inhibitor

no inhibitor

or

competitive

inhibitor

no inhibitor

noncompetitive

inhibition

competitive inhibition

0

V

[S]