Page 209 - The Manga Guide to Biochemistry

In this case, the inhibitor doesn’t block the substrate—it takes the enzymes out of the
game. Km is unaffected because it depends on substrate concentration. Instead, the maxi-
mum reaction rate will steadily decrease as the amount of inhibitor increases. The same
thing would happen if the enzyme concentration decreased.

This means that when a non-competitive inhibitor is added, the slope of the straight
line will again be greater on a Lineweaver-Burk reciprocal plot, as shown below. But unlike
competitive inhibition, the intersection with the y-axis will change, while the inters­ ection
with the x-axis will stay the same.

y If the slope Non-competitive
increases and
1 inhibition
Vmax changes

1
Vmax

-1 x
Km

Since inhibitors significantly affect enzyme reactions, they are often used in research
for elucidating enzyme structures or reaction mechanisms. They are also used in cancer
research by applying small amounts to inhibit enzymes that benefit the cancer cells.

Enzymes Are the Keys to Chemical Reactions 195