Industrial Biotransformations

v ˆ V max
‰SŠ
KM 1‡ ‰PŠ
KI ‡‰SŠ
5.2 Biocatalyst Kinetics
Non-competitive inhibitors bind only to the ES complex, leading to ESI complexes. The
binding of the inhibitor, which does not need to resemble the substrate, can be assumed
to cause a structural distortion, rendering the enzyme less active [Eq. (25)].
v ˆ V max
‰SŠ
KM ‡ 1‡ ‰IŠ
KI ‰SŠ
The linearization leads to Eq. (26):
1
v i
ˆ K M
V max
1
‰SŠ ‡
1‡ I
K I
V max
A special case of non-competitive inhibition is the substrate surplus inhibition, in which an
ESS complex is formed. Using the substrate concentration as the inhibitor concentration
in Eq. (25) gives Eq. (27):
v ˆ V max
‰SŠ
K M ‡‰SŠ‡ ‰SŠ2
K I
Non-competitive inhibitors can bind to the ES complex and to the free enzyme molecule.
It is therefore also referred to as mixed inhibition. The corresponding equation is Eq. (28):
v ˆ V max
1‡ ‰IŠ
K I
‰SŠ
…K M ‡‰SŠ†
The Lineweaver–Burk form is given in Eq. (29):
1
ˆ
1‡ I
2
6
4
KI 3
KM 7
5
1
‰SŠ ‡
1‡ I
KI v i
V max
V max
The inhibition schemes and equations are summarized in Table 5.1.
(24)
(25)
(26)
(27)
(28)
(29)
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