PROPERTIES OF ENZYMES
DR FAUZIA SHAOKAT
70140727

1.ENZYMES ARE PROTEINS
• All enzymes are proteins except a small group
of catalytic RNA molecules.
• Its catalytic activity is destroyed if enzyme is
denatured or dissociated into its subunits.

2.LOCATION WITHIN THE CELL
• Different enzymes are localized in specific
organelles within the cell
• This provides a favourable environment for the
reaction an organization of chemical pathway.
• For Example: enzyme for oxidation of
pyruvate,amino acids,fatty acids and for TCA cycle
are located in mitrochonrial matrix while enzymes
for glycolysis are present in cytosol.

3.ENZYME AFFECT REACTION RATES,NOT
EQUILIBRIUM
• Acting as a catalyst enzymes increases
rate of reaction but do not affect reaction
equilibrium.

4.CATALYSIS
• The reaction rate catalysed by enzyme is
enhanced in the range of 5 to 17.
• This enhancement occurs due to re-
arrangement of covalent bonds.

TWO TYPES OF INTERACTIONS OCCUR BETWEEN ENZYMES
AND SUBSTRATE TO LOWER THE ACTIVATION ENERGY
• 1.COVALENT INTERACTIONS:
• Catalytic functional groups (amino acid chain,metal
ions and co-enzymes) may form a transient
covalent bond with a substrate and activate it for
reaction.
• 2.NON COVALENT INTERACTIONS:
• Much of energy required to lower activation energy
is derived from weak,non covalent interactions.

BINDING ENERGY
• Formation of ES complex is accompanied by
release of small amount of free energy that
stabilizes the interaction.
• Binding energy is a major source of free
energy used by enzymes to lower the
activation energy.

5.CONTRIBUTION OF SPECIFIC CATALYTIC
GROUPS TO CATALYSIS
• Once a substrate is bound to an enzyme,
catalytic functional groups aid in the cleavage
and formation of bonds by following
mechanisms:
• 1.GENERAL ACID BASE CATALYSIS
• 2.COVALENT CATALYSIS
• 3.METAL ION CATALYSIS

6.SPECIFICITY
• Enzymes are very specific as they readily
discriminate between substrate with quite
similar structure.
• Binding energy contributes to specificity of an
enzyme.

• IF an enzymes active site has functional group
arranged optimaly to form a weak interactions with
a paticular substrate the enzyme will not be able to
ineract to the same degree with any other
molecule.
• IF substrate has a hydroxyl group thats forms a
hydrogen bond with a specific Glu residue on an
enzyme any molecule lacking a hydroxyl group at
that particular position will be poorer substrate for
enzyme.

DIFFERENT TYPES OF SPECIFICITY ARE :
• 1.STEREOCHEMICAL:
• D and L amino acids.
• 2.REACTION SPECIFICITY:
• Oxalo acetic acid undergo several reactions but is catalyed by its
own seperate enzyme.
• 3.SUBSTRATE SPECIFICITY:
• 3.1) ABSOLUTE
• 3.2) RELATIVE
• a) GROUP DEPENDENT
• b) BOND SPECIFICITY

7.MODIFICATION OF ENZYMES
• Enzymes are modified covalently by
phosphorylation, glycosylation and other
processes.
• These alterations are involved in the regulation of
enzyme activity so that the rate of product
formation responds to cellular need.

8.PROENZYME
• An inactive precursor of an enzyme is called a
zymogen.
• It is cleaved to form active enzyme.
• Chymotrypsin and trypsin are initially syenthsized
as chymotrypsinogen and trypsinogen.
• Specfic clevage causes confirmational change that
expose the enzyme active site.

9.ISOENZYMES
• Two or more enzymes that catalyse the same reacion but
are encoded by different genes are called isoenzymes.
• For Example: lactate dehydrogenase has five different
isoenzymes.
• Each type contain different ratio of two kinds of
polypeptides.
• The M (for muscle) chain and the H (for heart) chain and
encoded by two different genes.