In biology and biochemistry,
the active site of an enzyme
is a region to which another molecule
or molecules can bind. This molecule is called the substrate.
The shape of the active site allows this particular substrate to fit correctly,
and to be held in place by temporary bonds.
The active site in many enzymes can be inhibited or suppressed by the presence
of another molecule. There are two ways in which this can occur. In competitive
inhibition, the
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active site itself is blocked when a molecule similar in shape to the substrate
bonds to the active site and cannot be processed by the enzyme. In noncompetitive
inhibition, a molecule bonds to the enzyme at another site, the allosteric site,
and this bond causes the enzyme to transform such that the active site is rendered
useless. Often certain metabolic pathways are designed such that after several
stages negative
feedback will cause the inputs of the system to become reduced. There are
two theories of how enzymes work: the lock and key mechanism and an alternative
theory whereby the active site binds and encloses onto the substrate molecule.
Often enzymes bond to their substrate by Van
der Waals forces or hydrogen bonds between the R' groups in the amino acid
monomers.
