ABSTRACT
Enzymes are catalysts, which speed the rate of a reaction
without being altered themselves. Typically, enzymes are
proteins, although enzymatic activity by nucleic acids has
been observed. Enzymes are employed in a wide range of
processing steps in agricultural, food, environmental, and
biotechnological industries. Examples range from the use
of amylase to cleave starch into simple sugars to the use of
restriction endonucleases to cleave DNA. The most
remarkable properties of enzymes are their high catalytic
power, their specificity (each enzyme catalyzes only one
type of reaction), and their high degree of regulation. Their
catalytic power can be tremendous, with some enzymes
reported to increase the rate of a reaction by as much as
ASSAYS OF ENZYMATIC ACTIVITY
An enzyme is most easily characterized by observation of
the rate with which it catalyzes a specific chemical reac-
tion. For stoichiometric conversion of substrate to pro-
duct, the reaction rate can be determined by either
monitoring the loss of substrate being consumed in the
reaction or following the formation of product. The latter
is preferred as it involves the increase of a signal from
zero, rather than a decrease of a substrate concentration
from a high value.[2]
Continuous assays in which product concentrations are
frequently sampled provide an ideal approach for quantify-
ing the rate at which an enzymatic reaction proceeds, also
called the kinetics. These methods can be automated to
provide substantial information in a short period of time.
Direct, continuous assays often involve non-destructive
methods such as spectroscopic measurement of alterations
