Important Factors That
Influence Enzyme Activity
Creator : Lyubomir Penelov
Enzymes are essential for almost all the
chemical reactions that take place inside
living cells. However, the activities of the
enzymes can be enhanced or inhibited by
a number of factors. In this article, we are
talking about all those factors that affect
enzyme activity.
Enzyme Activity Explained
 An enzyme can increase the speed of a chemical reaction manifold.
You will be surprised to know that studies have found that it can
make a chemical reaction 10 billion times faster. The chemical
substances that are present at the start of a biochemical process is
termed as substrates which undergo chemical change(s) to form
one or more end products. Basically, the active site of the enzymes
forms a temporary bond with the substrate. During this time, an
enzyme lowers the activation energy of the participant molecules
which in turn speeds up the reaction. After the reaction is over, the
newly formed product leaves the surface of the enzyme and the
enzyme gets back its original shape. Thus, you can say it
participates in the reaction without undergoing any physical or
chemical change. Therefore, the same enzyme is used again and
again for the specific process.
Human glyoxalase I. Two zinc ions that are needed for the enzyme
to catalyze its reaction are shown as purple spheres, and
an enzyme inhibitor called S-hexylglutathione is shown as a spacefilling model, filling the two active sites
Factors
Influencing
Enzyme
Activity
Change in Temperature
 All enzymes need a favorable temperature to work properly. The
rate of a biochemical reaction increases with rise in temperature.
This is because the heat enhances the kinetic energy of the
participant molecules which results in more number of collisions
between them. On the other hand, it is mostly found that in low
temperature conditions, the reaction becomes slow as there is less
contact between the substrate and the enzyme. However, extreme
temperatures are not good for the enzymes. Under the influence of
very high temperature, the enzyme molecule tends to get distorted,
due to which the rate of reaction decreases. In other words, a
denatured enzyme fails to carry out its normal functions. In the
human body, the optimum temperature at which most enzymes
become highly active lies in the range of 95 °F to 104 °F (35 °C to
40 °C). There are some enzymes that prefer a lower temperature
than this.
Change in pH Value
 The efficiency of an enzyme is largely influenced by the pH value of
its surroundings. This is because the charge of its component amino
acids changes with the change in the pH value. Each enzyme
becomes active at a certain pH level. In general, most enzymes
remain stable and work well in the pH range of 6 and 8. However,
there are some specific enzymes which work well only in acidic or
basic surroundings. The favorable pH value for a specific enzyme
actually depends on the biological system in which it is working.
When the pH value becomes very high or too low, then the basic
structure of the enzyme undergoes change(s). As a result, the active
site of the enzyme fails to bind well with the substrate properly and
the activity of the enzyme gets badly affected. The enzyme may
even stop functioning completely.
Substrate Concentration
 Substrate concentration plays a major role in various
enzyme activities. This is obviously because higher
concentration of substrate means more number of
substrate molecules are involved with the enzyme
activity. Whereas, a low concentration of substrate
means less number of molecules will get attached to the
enzymes. This in turn reduces the enzyme activity. When
the rate of an enzymatic reaction is maximum and the
enzyme is at its most active state, an increase in the
concentration of substrate will not make any difference in
the enzyme activity. In this condition, the substrate is
continuously replaced by new ones at the active site of
the enzyme and there is no scope to add those extra
molecules there.
Enzyme Concentration
 In any enzymatic reaction, the quantity of substrate molecules
involved is more as compared to the number of enzymes. A rise in
enzyme concentration will enhance the enzymatic activity for the
simple reason that more enzymes are participating in the reaction.
The rate of the reaction is directly proportional to the quantity of
enzymes available for it. However, that does not mean that a
constant rise in concentration of enzymes will lead to a steady rise
in the rate of reaction. Rather, a very high concentration of enzymes
where all the substrate molecules are already used up does not
have any impact on the reaction rate. To be precise, once the rate of
reaction has attained stability, an increase in the quantity of
enzymes does not affect the rate of reaction anymore.
Inhibitors
 As the name suggests, inhibitors are those substances
that have a tendency to prevent activities of the
enzymes. Enzyme inhibitors interfere with the enzyme
functions in two different ways. Based on this, they are
divided into two categories: competitive inhibitors and
noncompetitive inhibitors. A competitive inhibitor has a
structure which is the same as that of a substrate
molecule, and so it gets attached to the activated center
of the enzyme easily and restricts the bond formation of
enzyme-substrate complex. A noncompetitive inhibitor is
the one which brings about change(s) in the shape of the
enzymes by reacting with its active site. In this condition,
the substrate molecule cannot bind itself to the enzyme
and thus, the subsequent activities are blocked.
Allosteric Factors
 There are some enzymes which have one active site and
one or more regulatory sites and are known as allosteric
enzymes. A molecule that binds with the regulatory sites
are referred to as allosteric factor. When this molecule in
the cellular environment forms a weak noncovalent bond
at the regulatory site, the shape of the enzyme and its
activation center get modified. This change usually
decreases the enzyme activity as it inhibits the formation
of a new enzyme-substrate complex. However, there are
some allosteric activators that promote the affinity
between the enzyme and the substrate and influence
enzymatic behavior positively.
I hope you enjoyed my article.
Have a good day students