Specificity is the term used to define the selectivity of enzymes
for their substrates. The selective qualities of an enzyme are collectively recognized as its specificity.
Other texts have synonymised enzyme selectivity with substrate specificity:
The non-covalent forces through which substrates and other molecules bind to enzymes are similar in character to the forces
that dictate the conformations of the proteins themselves : Both involve van der Waals, electrostatic, hydrogen
bonding, and hydrophobic interactions.
Molecules that differ in shape or functional group distribution
from the substrate cannot productively bind to the
enzyme; that is, they cannot form enzyme–substrate complexes
that lead to the formation of products.
The extraordinary ability of an enzyme to catalyse only one particular reaction is a quality known as specificity.
Specificity means an enzyme acts only on a specific substance,
its substrate, invariably transforming it into a specific product. That is, an enzyme
binds only certain compounds, and then, only a specific reaction ensues.
Some enzymes show absolute specificity, catalyzing the transformation of only one
specific substrate to yield a unique product. Other enzymes carry out a particular
reaction but act on a class of compounds. For example, hexokinase (ATP-hexose-6-
phosphotransferase) will carry out the ATP-dependent phosphorylation of a number
of hexoses at the 6-position, including glucose.
Pioneering enzyme specificity studies at the turn of the 20th century
by the great organic chemist Emil Fischer led to the notion of an
enzyme resembling a “lock” and its particular substrate the “key.”
The specificity of an enzyme (the lock) for its substrate (the key) arises from their geometrically complementary shapes. This was later
modified to a more accurate induced fit hypothesis given the high
flexibility, conformationally dynamic properties of enzyme molecules.
- Voet and Voet Biochemistry 4th ed: Introduction to Enzymes
- Biochemistry Grisham & Garret How Can Enzymes Be So Specific?