An enzyme is a protein functioning as a biological
catalyst. Enzymes accelerate (often by several orders
of magnitude) chemical reactions in the cell that
would proceed imperceptibly or not at all in their
absence. The enzyme is not permanently modified by
Most enzymes demonstrate great
specificity, reacting with only one or small group
of closely related chemical compounds, thus, sometimes
several enzymes are required for efficient catalytic
function. Some enzymes depend on the presence of Coenzymes
for their function.
For the enzyme to continue to
be effective, its three-dimensional molecular structure
must be maintained. X-ray crystallography is used
to analyze the structure of enzymes.
Over 1000 different
enzymes have been identified, and the exact sequence
of Amino Acids (subunits of protein) has been determined
for many proteins since 1967, when the first such
determination was made.
It is believed that enzymes
function by attaching the substrate molecule to a
specific molecular site, so that electrostatic forces
of nearby atoms sharply reduce the energy needed to
cleave and re-form the appropriate chemical bonds.