FACTORS AFFECTING ENZYME ACTIVITY

The factors affecting enzyme activity include temperature, pH, substrate concentration, enzyme
concentration, and the presence of inhibitors or activators. Enzymes are biological catalysts that
accelerate chemical reactions in living organisms. Enzymes are made up of proteins that are highly
specific and crucial for physiological processes.

Understanding these factors is essential for optimizing enzyme function and maintaining biological
processes in balance. In this article, you will factors affecting enzyme activity notes.

Enzymes Meaning and Definition

Enzyme Definition: Enzymes are protein molecules that functions as biological catalysts and helps
accelerate chemical reactions essential for life.

Most enzymes are made up of proteins except ribozymes. All metabolic pathway processes are
catalysed by intracellular enzymes. They play a crucial role in various bodily functions
including digestion and metabolism. Enzymes function by lowering the activation energy required for
a reaction to occur, allowing it to happen more quickly and efficiently. Enzymes degrade substrates
into simpler molecules known as products. Each enzyme is highly specific, recognizing and binding to
a particular substrate molecule to catalyze a specific reaction.

What are the Factors Affecting Enzyme Activity?

The reaction conditions have a significant impact on enzyme activity. Enzymes functions effectively
under the optimal conditions. Enzyme activity can be influenced by various factors such as
temperature, pH, enzyme concentration, substrate concentration, inhibitor, or accumulation of end
products. These factors can alter the shape and structure of the enzyme, affecting its ability to bind to
the substrate and catalyze the reaction efficiently. These factors are discussed below:
FACTORS AFFECTING ENZYME ACTIVITY

EFFECT OF TEMPERATURE ON ENZYME ACTIVITY

• Changing air temperature can have a significant impact on the metabolism of living organisms
due to the effect of temperature on enzyme activity

• Enzymes have a specific optimum temperature

o This is the temperature at which they catalyse a reaction at the maximum rate
• Lower temperatures either prevent reactions from proceeding or slow them down
o Molecules move relatively slowly as they have less kinetic energy
o Less kinetic energy results in a lower frequency of successful
collisions between substrate molecules and the active sites of the enzymes which
leads to less frequent enzyme-substrate complex formation
o Substrates and enzymes also collide with less energy, making it less likely for bonds to
be formed or broken
• Higher temperatures cause reactions to speed up
o Molecules move more quickly as they have more kinetic energy
o Increased kinetic energy results in a higher frequency of successful collisions between
substrate molecules and the active sites of the enzymes which leads to more
frequent enzyme-substrate complex formation
o Substrates and enzymes also collide with more energy, making it more likely for bonds
to be formed or broken
Denaturation

• If temperatures continue to increase past a certain point, the rate at which an enzyme
catalyses a reaction drops sharply as the enzymes begin to denature
o The increased kinetic energy and vibration of an enzyme puts a strain on its bonds,
eventually causing the weaker hydrogen and ionic bonds that hold the enzyme
molecule in its precise shape to start to break
o The breaking of bonds causes the tertiary structure of the enzyme to change
o The active site is permanently damaged and its shape is no longer complementary to
the substrate, preventing the substrate from binding
o Denaturation has occurred if the substrate can no longer bind
FACTORS AFFECTING ENZYME ACTIVITY
At high temperatures enzymes can denature

The rate of an enzyme catalysed reaction is affected by temperature. Note that 35 C is not the
optimum temperature for all enzyme-controlled reactions.

The optimal temperature of an enzyme is the specific temperature at which it exhibits peak activity.
This temperature varies among enzymes and is influenced by the environment in which the enzyme
operates.

General Optimal Temperature Ranges:

• Human Enzymes: Typically, human enzymes function most efficiently around 37°C (98.6°F),
which corresponds to normal body temperature.
• Plant Enzymes: Optimal temperatures for plant enzymes generally fall between 20°C and 30°C
(68°F to 86°F).
• Microbial Enzymes: Microorganisms exhibit a wide range of optimal temperatures:
o Mesophilic Microbes: Enzymes from these organisms have optimal temperatures
between 20°C and 45°C (68°F to 113°F).
o Thermophilic Microbes: Enzymes from heat-loving organisms can have optimal
temperatures as high as 70°C (158°F) or more.
Source of the Enzyme: Enzymes have evolved to function best at the temperature’s characteristic of
their native environments. For instance, enzymes from thermophilic organisms are adapted to high
temperatures, whereas those from mesophilic organisms, like humans, are optimized for moderate
temperatures.

Conclusion:

Understanding the optimal temperature of an enzyme is crucial for applications in biotechnology,

medicine, and research, as operating outside this temperature can lead to reduced efficiency or
denaturation of the enzyme.
FACTORS AFFECTING ENZYME ACTIVITY
EFFECT OF ENZYME CONCENTRATION ON ENZYME ACTIVITY
• Enzyme concentration directly affects enzyme activity by influencing the number of enzyme
molecules available to catalyze reactions.

• Increasing enzyme concentration leads to more active sites available for substrate binding,
thereby increasing the rate of reaction.

• This occurs because higher enzyme concentrations result in more collisions between enzymes
and substrates, leading to more successful enzyme-substrate complexes being formed.

• However, once all substrate molecules are bound to enzymes, further increases in enzyme
concentration will not significantly affect the reaction rate, as the active sites become
saturated.

• Conversely, decreasing enzyme concentration leads to fewer active sites available for substrate
binding, resulting in a slower rate of reaction.

Effect of Enzymes Concentration on Enzyme Activity

Effect of Substrate Concentration on Enzyme Activity

• Substrate concentration directly influences enzyme activity by affecting the rate of enzyme-
substrate complex formation.

• Initially, as substrate concentration increases, the rate of reaction also increases because more
substrate molecules are available to bind with enzyme active sites.

• This occurs until all enzyme active sites are saturated with substrate, leading to maximum
reaction velocity (Vmax).
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• At this point, further increases in substrate concentration do not increase the reaction rate
because all enzyme active sites are already engaged.

• Conversely, when substrate concentration decreases, fewer substrate molecules are available
to bind with enzyme active sites, resulting in a slower rate of reaction.

EFFECT OF PH VALUE ON ENZYME ACTIVITY

The pH scale is used to measure the acidity or alkalinity of a sample and describes how many hydrogen
ions or hydroxides are present in the sample. The change of pH will lead to the ionization of amino
FACTORS AFFECTING ENZYME ACTIVITY
acids atoms and molecules, change the shape and structure of proteins, thus damaging the function
of proteins. Enzymes are also proteins, which are also affected by changes in pH. Very high or very low
pH will lead to the complete loss of the activity of most enzymes. The pH value at which the enzyme
is most active is called the optimal pH value.

pH Effects Enzyme Activity

The structure of the enzyme has a great influence on the activity of the enzyme. In other words,
changes in the structure of the enzyme affect the rate of chemical reactions.

When the pH value of the reaction medium changes, the shape and structure of the enzyme will
change. For example, pH can affect the ionization state of acidic or basic amino acids.

There are carboxyl functional groups on the side chain of acidic amino acids. There are amine-
containing functional groups in the side chain of basic amino acids.

If the ionized state of amino acids in the protein is changed, the ionic bonds that maintain the three-
dimensional shape of the protein will change. This may lead to changes in protein function or
inactivation of enzymes.

pH Effects Substrates

PH not only affects the activity of the enzyme, but also affects the charge and shape of the substrate,
so that the substrate cannot bind to the active site, or cannot be catalyzed to form a product.

In a narrow range of pH, the structural and morphological changes of enzymes and substrates may be
reversible. However, if the level of pH changes significantly, the enzyme and substrate may be
denatured. In this case, the enzyme and the substrate do not recognize each other, so there will be no
reaction.

Optimal pH

All enzymes have an ideal pH value, which is called optimal pH. Under the optimum pH conditions,
each enzyme showed the maximum activity. For example, the optimum pH of an enzyme that works
in the acidic environment of the human stomach is lower than that of an enzyme that works in a
neutral environment of human blood.
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When the pH value deviates from the ideal conditions, the activity of the enzyme slows down and then
stops. The enzyme has an active site at the substrate binding site, and the shape of the active site will
change with the change of pH value.

Depending on the extreme extent of the enzyme and pH changes, these changes may permanently
"destroy" the enzyme, or once the conditions return to the desired range of the enzyme, the enzyme
will return to normal.

INHIBITORS
Inhibitors are compounds that cause enzymes to lose activity, either by slowing or stopping the
chemical reaction. Some inhibitors cause temporary loss of activity, while others cause permanent loss
of activity.

Competitive inhibitors: these inhibitors are similar in structure to that of the substrate. It competes
for the same active site as that of the substrate.

The inhibitors bind the active site and stop the substrate in binding. Thus, the enzyme activity is
declined due to the non-formation of enzyme substrate complex.

The inhibitor is not acted on by the enzyme but does prevent the substrate from approaching the
active site.

The degree to which a competitive inhibitor interferes with an enzyme’s activity depends on the
relative concentrations of the substrate and the inhibitor.

If the inhibitor is present in relatively large quantities, it will initially block most of the active sites.
Increasing the substrate concentration promotes displacement of the inhibitor from the active site.
Competitive inhibition can be completely reversed by adding substrate so that it reaches a much higher
concentration than that of the inhibitor.

Non-competitive inhibitors: These inhibitors bind at the different site of the enzyme and reduce the
activity of the enzyme.

The attachment of the non-competitive inhibitor to the allosteric site results in a shift in three-
dimensional structure that alters the shape of the active site so that the substrate will no longer fit in
the active site properly.
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A noncompetitive inhibitor can combine with either the free enzyme or the enzyme-substrate complex
because its binding site on the enzyme is distinct from the active site.

Because the inhibitor does not structurally resemble the substrate, the addition of excess substrate
does not reverse the inhibitory effect. Even if the substrate binds to the enzyme, the enzyme is no
longer fit to catalyse the reaction as the inhibitor causes some changes in the enzyme. Thus, the
function of enzymes is made ineffective.

INHIBITION OF BIOCHEMICAL PATHWAYS

Feedback inhibition: Another way a metabolic pathway can be controlled is by feedback inhibition.
This is when the end product in a metabolic pathway binds to an enzyme at the start of the pathway.
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This process stops the metabolic pathway and so prevents further synthesis of the end product until
the end product concentration decreases. The higher the concentration of end product, the quicker
the metabolic pathway stops.

COENZYMES
Coenzymes are organic molecules that help enzymes perform their functions. They are often derived
from vitamins and are essential for many biochemical reactions.

A coenzyme is a molecule required by a particular enzyme to carry out the catalysis of a chemical
reaction. Many are derived from vitamins, particularly those that are phosphorylated derivatives of
water-soluble vitamins. Coenzymes participate in catalysis when they bind to the active site of the
enzyme (called apoenzyme) and subsequently form the active enzyme (called holoenzyme). Although
coenzymes activate enzymes they are not considered as substrates of the reaction. The main function
of the coenzyme is to act as an intermediate carrier of transferred electrons or functional groups in a
reaction.