enzyme

1. Enzymology
Cihan University - Erbil
College of Health Technology
Department of Medical Biochemical Analysis
Lec. 1
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2.  At the end of the nineteenth century, a debate was raging as to whether the
process of ethanol formation required the presence of intact yeast cells.
 In 1897, Eduard Büchner, discovered that fermentation was producing ethanol and
bubbles of carbon dioxide. Büchner had shown that fermentation did not require
the presence of intact cells.
 It was soon found, however, that fermentation was very
different from the types of reactions carried out by
organic chemists.
 Fermentation required the presence of a unique set of
catalysts that had no counterpart in the nonliving
world. These catalysts were called enzymes (after the
Greek for “in yeast”).
Introduction
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3.  Enzymes are the mediators of metabolism, responsible for virtually every reaction
that occurs in a cell.
 Without enzymes, metabolic reactions would proceed so slowly as to be
imperceptible.
 The first evidence that enzymes are proteins was obtained in 1926 by James
Sumner of Cornell University, when he crystallized the enzyme urease from jack
beans and determined its composition.
 Eventually, it became evident that certain biological reactions are catalyzed by RNA
molecules. For the sake of clarity, the term enzyme is still generally reserved for
protein catalysts, while the term ribozyme is used for RNA catalysts.
Introduction
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4.  The Properties of Enzymes
o As is true of all catalysts, enzymes exhibit the following properties:
(1) They are required only in small amounts;
(2) They are not altered irreversibly during the course of the reaction, and therefore
each enzyme molecule can participate repeatedly in individual reactions.
(3) They have no effect on the thermodynamics of the reaction.
 This last point is particularly important. Enzymes do not supply energy for a chemical
reaction and therefore do not determine whether a reaction is thermodynamically
favorable or unfavorable.
 Similarly, enzymes do not determine the ratio of products to reactants at equilibrium.
These are inherent properties of the reacting chemicals.
 As catalysts, enzymes can only accelerate the rate at which a favorable chemical
reaction proceeds.
Introduction
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5.  Enzymes are critical for every aspect of cellular life:
 Cell shape and motility
 Surface receptor
 Cell cycle
 Metabolism
 Transcription
 Hormone release
 Muscle contraction
 Protein synthesis
Importance of enzymes
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6.  The study of enzymes has immense practical importance. In some
diseases, especially inheritable genetic disorders, there may be a
deficiency or even a total absence of one or more enzymes.
 For other disease conditions, excessive activity of an enzyme may be the
cause.
 Measurements of the activities of enzymes in blood plasma,
erythrocytes, or tissue samples are important in diagnosing certain
illnesses.
 Lactate dehydrogenase (LDH) is normally not found in high levels in
blood, as it is produced in cells
 – Increased levels of LDH in the blood indicate
myocardial infarction (MI) (Heart attack)
Medical Uses of Enzymes
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7.  Many drugs exert their biological effects through interactions with enzymes.
• There is no direct test to measure urea in the blood
– Urease converts urea into ammonia, which is easily measured
& is used as urea indicator
• Blood Urea Nitrogen (BUN) is used to measure kidney function
– High urea levels in the blood indicate kidney malfunction
– Tissue plasminogen activator (TPA) activates the enzyme plasminogen that
dissolves blood clots
• Used in the treatment of MI (myocardial infarction).
Medical Uses of Enzymes
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8.  The ability to detect and to quantify the activity of specific enzymes in
blood, other tissue fluids, or cell extracts provides information that
complements the physician’s ability to diagnose and predict the prognosis
of many diseases.
 Further medical applications include changes in the quantity or in the
catalytic activity of key enzymes that can result from genetic defects,
nutritional deficits, tissue damage, toxins, or infection by viral or bacterial
pathogens (eg, Vibrio cholerae).
 Medical scientists address imbalances in enzyme activity by using
pharmacologic agents to inhibit specific enzymes and are investigating
gene therapy as a means to remedy deficits in enzyme level or function
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Medical Uses of Enzymes

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11.  Enzymes are important practical tools, not only in medicine but in the
chemical industry, food processing, and agriculture.
 Proteases and amylases augment the capacity of detergents to remove dirt
and stains, and enzymes play important roles in producing or enhancing the
nutrient value of food products for both humans and animals.
 The protease rennin, for example, is utilized in the production of cheeses
while lactase is employed to remove lactose from milk for the benefit of
lactose-intolerant persons deficient in this hydrolytic enzyme.
 Finally, stereospecific enzyme catalysts can be of particular value in the
biosynthesis of complex drugs or antibiotics.
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12.  Enzymes act like a functional biocatalyst that only cause catalysis of distinct
substrates into particular products and allow the reaction to occur at an
increased rate without being consumed.
 Thus, the enzyme’s primary function is to accelerate the reaction rate.
 Enzymes neither affect the nature of products formed nor undergo any
changes by the reaction catalyzed.
 Only the active site of an enzyme goes through certain conformational changes
during the substrate binding
General Properties of Enzyme
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13.  Enzymes are biomolecules that are highly specific.
 All metabolic processes in our body need enzymes to catalyze reaction at a faster
rate.
 Enzymes are naturally produced by living cells, unlike catalysts
 Enzymes are larger than substrates.
 Enzymes reside within the protoplasm as hydrophilic colloids.
 Enzymes are present in all body cells, and each function in a specific reaction.
 Enzymes catalyze all essential reactions (oxidation, reduction, hydrolysis,
esterification, synthesis, molecular interconversion) that supply the energy and/or
chemical changes necessary for vital activates (muscle contraction, nerve conduction,
respiration, digestion, growth, reproduction, maintain of the body temperature).
General Properties of Enzyme
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14. General Properties of Enzyme
The general properties of enzyme include the following characteristics:
•Enzymes initiate and accelerate the reaction.
•The activity of an enzyme is pH-specific.
•Enzymes can catalyze reactions in a forward and reverse manner, but do not decide the
direction of the biochemical pathway.
•An enzyme possesses a specialized region (active site), to which substrate specifically
interacts to form desired products.
•Under high heat, temperature and varying pH, an enzyme becomes unstable.
•Enzymes are proteinaceous possessing properties characteristic to proteins.
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15. General Properties of Enzyme
 A small amount of enzyme is required to bring catalysis of substrates.
 Some enzymes are regulatory in function.
 Its primary function is to minimize the activation energy.
 The enzymes remain unaltered during and after the product formation, or
they can be reconsumed.
 An enzyme may possess an allosteric site besides an active site, to which
cofactors or regulators interact.
 Enzymes are soluble in water and NaCl
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16. Enzymes as Biocatalysts
 Reasons that why enzymes are regarded as “Biocatalysts” are as follows:
 Like catalysts, enzymes speed up the reaction rate by reducing the transition time
between the substrate and product.
 As catalysts, enzymes also regulate reaction-specificity, in which only specific
substrate adhere to an enzyme’s active site to bring product formation.
 Similar to the function of catalysts, enzymes only take part in the biochemical
reaction without being consumed or altering the equilibrium state.
 Like catalysts, enzymes influence or initiate the biochemical reaction by lowering
the activation energy and increase the transition energy of substrate into product.
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17. Physical Properties of Enzyme
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18.  Biocatalyst Nature
 Enzymes serve as a biocatalyst, and the reasons we have discussed earlier
in this lecture.
Physical Properties of Enzyme
 Enzyme Activity
 The mechanism of enzyme action strongly depends upon the factors like
temperature, pH, and concentration of enzyme and substrate.
 A higher concentration of enzyme will result in faster enzymatic activity,
as more substrates will interact with the enzyme’s active site to bring
product formation.
 Once the reaction velocity reaches a maximum value, there would not be
any changes in the enzymatic reaction even after the addition of enzyme
and substrate.
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19.  Colloidal Nature
 Enzymes behave as colloids due to their large size or high molecular weight. As a
result, the enzymes have a little or no tendency to dialyze or cross the semi-
permeable membrane.
)A colloid is a mixture in which one substance consisting of microscopically dispersed
insoluble particles is suspended throughout another substance(.
 Enzyme Precipitation
 Acidic and alkaline solution can cause enzyme precipitation, as the enzymes
are amphoteric (possess amino and carboxylic acid group towards the end of the
chain). Ethanol and a high concentration of inorganic salts like ammonium
sulphate facilitate enzyme precipitation.
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Physical Properties of Enzyme

20.  Molecular Weight
 Enzymes are large protein biomolecules possessing a polypeptide chain of various
amino acid sequence. Nearly 200 to 300 peptide bonds hold the amino acids together.
Therefore, enzymes have a high molecular weight.
 Enzyme Solubility
 Enzymes are soluble in water, NaCl, diluted glycerol and alcohol.
 Enzyme Denaturation
 High heat (above 40 degrees Celsius) and alternations in the pH (too low and too
high), heavy metals, and high salt concentration etc., denatures the enzyme by
breaking the intra and inter-molecular noncovalent bonds. It distorts the enzyme’s
shape and active site and finally results in the loss of enzyme activity 20
Physical Properties of Enzyme