The three mechanisms of enzyme inhibition
that I have talked about so far
competitive inhibition, non-competitive
inhibition and uncompetitive inhibition
are fundamentally different from the one
I am getting ready to talk about here.
In each of those cases, the binding of the
inhibitor to the enzyme was a reversible process.
The inhibitor could go on. But the inhibitor could also
come off and these are very common inhibition mechanisms.
The mechanism I am getting ready to
describe here called suicide inhibition
is different completely from them.
In suicide inhibition, what happens is
the inhibitor that binds with
the enzyme does so irreversibly.
And it does it irreversibly; because, the inhibitor makes
a covalent bond with the enzyme at the active site.
The enzyme can't shake and the inhibitor loose
and as a consequence the enzyme
is completely put out of action.
Now example of a reaction
like this occurring is that
of the action of penicillin
which we used to kill bacteria.
Penicillin works; because, what it does is it inhibits
the bacterium's ability to make cell walls.
Well cell walls are pretty important for cells;
because, without a wall you don't have a cell.
The way that this works, is penicillin
mimics the normal substrate
that the enzyme that makes the cell walls
uses, that's the pentaglycine chain.
Because penicillin resembles it and the enzyme
binds to it, like it would bind to the normal substrate,
but penicillin makes the covalent bond.
So when suicide inhibition, the enzyme is completely
destroyed and never gets a chance to come back into its thing.
Well in this series of lectures
what I have talked about
are different types of inhibition. A reversible
set of inhibitions that included: the competitive,
non-competitive and uncompetitive.
And now suicide inhibition that is
an irreversible enzyme inhibition.
Our understanding of enzyme inhibition is
important for anyone interested in understanding
the mechanism by which drugs work
or designing drugs themselves.