The study of the rates of enzyme-catalyzed reactions.
Rates of reaction are usually measured by using
the purified enzyme in vitro with the substrate and
then observing the formation of the product or disappearance
of the substrate.
As the concentration of the substrate
is increased the rate of reaction increases proportionally
up to a certain point, after which any further increase
in substrate concentration no longer increases the
reaction rate. At this point, all active sites of
the enzyme are saturated with substrate; any further
increase in the rate of reaction will occur only if
more enzyme is added.
Reaction rates are also affected
by the presence of inhibitors, temperature and pH.