Enzymes, coenzymes and isoenzymes

In this lesson we are going to be discussing Enzymes, their characteristics, classification as well as co-factors and co-enzymes.

1. ENZYMES
BY
OKECHUKWU FRANCIS (M.SC)

2. •OBJECTIVES;
•Definition of enzymes
•Characteristics of enzymes.
•Enzymes and how they work?
•Classification of enzymes
•Mode of actions of enzymes
•Coenzymes
•What are isoenzymes? Examples and roles in functional disorders.

3. ENZYMES arebiologicalcatalystsPRODUCED bybiologicalcells,
theyspeeduptherateofcellularprocessesorreactions.Theyare
wholeinformandcanbeeasilydestroyedbyheat.
Usually,areactionlikeproteinHydrolysis(breakdown)byastrong
acidat100°cwouldtakeatleast24hourstocompletebutinthe
presenceoftheenzyme“Pepsin”intheintestinesuchreactions
wouldtakeamatterofminutes.
Imagineenzymeswasn’tpresentinoursystem,thesereactions
woulddelayforageshencecellswhichrequirethesenutrients
obtainedtosurvivewoulddiebeforethesenutrientsgetstothem.

4. •CHARACTERISTICS OF ENZYMES
•Some general characteristics of enzymes includes;
1. All enzymes are protein in nature except RNA acting as Ribozymes.
2. Enzymes are specific in nature hence they all bind to a particular
substrate.
3. Enzymes remains unchanged at the end of each chemical reactions
hence the formation of the product from a certain substrate doesn’t
affect the nature of an enzymes.

5. HOWENZYMES WORK;
Enzymesfunctionbyreducingtheactivationenergyofareaction
(energyrequiredtokickstartareaction),henceenzymaticprocess
proceedsfasterutilizinglessenergyascomparedtoanon-enzymatic
processwhichwouldhavetotakemoretimeforsuchhighactivation
energytobereached.
Asimplemechanism ofbringing
Bothsubstratesandreaction
Conditionstoaclosercontact
Wasbestexplainedbythelockand
Keymodelasseeninthediagram.
Eachenzymehasaspecific
Substrateitbindsto,resultingina
Productsynthesis.

6. •CLASSIFICATION OF ENZYMES;
•Early enzymes to be isolated and named e.gtrypsin, pepsin and chymotrypsin give no
information about the reaction they catalyzed. This would create ambiguity in the nearest
future hence in 1961 an enzyme commission was set up to develop a proper naming pattern
for enzymes. This commission classified enzymes into 6 main classes according to the type of
reaction they catalyzed.
•The enzymes commission number format EC: a.b.c.dwas also introduced where EC stands
for Enzyme commission, a standards for main-class, b for sub-class, c for sub-sub class and d
for position of the enzyme in the main class.
•Hence an enzyme like lactase dehydrogenase which catalyzes the anaerobic production of
lactic acid from pyruvate would have an enzyme commission number EC:1.1.1.27

7. 1. OXIDOREDUCTASES: ENZYMES
INVOLVED IN OXIDATION-REDUCTION
REACTIONS.
Here gly-3-phosphate is
reduced to 1,3 PGA IN AN
OXIDOREDUCTION REACTION
BY THE ACTION OF GLY-3-
PHOSPHATE DEHYDROGENASE.

8. 2. TRANSFERASES: ENZYMES THAT
CATALYZE THE TRANSFER OF FUNCTIONAL
GROUPS.

9. 3. HYDROLASES: ENZYMES THAT BRING
ABOUT HYDROLYSIS OF VARIOUS
COMPOUNDS.

10. 4. LYASES: ENZYMES SPECIALIZED IN THE
BREAK OR SPLITTING OF BONDS IN A
PROCESS OTHER THAN HYDROLYSIS.
Here fructose 1,6-bisphosphate is broken down to 2 triose
phosphates namely without utilizing water like in hydrolysis.

11. 5. ISOMERASES: ENZYMES INVOLVED IN
ISOMERIZATION REACTIONS.
ENZYME NAME: PHOSPHOR TRIOSE ISOMERASE.

12. 6. LIGASES: ENZYMES CATALYZING THE
SYNTHETIC TWO MOLECULES JOINED
TOGETHER AND ATPIS USED.
pyruvate is carboxylatedin cellular organisms during
gluconeogenesis and other metabolic processes by the enzyme
pyruvate carboxylase in the presence of bicarbonate. ATP is utilized
in this process.

13. COENZYMES/COFACTORS;
•Acofactoris a non-protein chemical compoundormetallic ion
that is required for an enzyme’s activity. Cofactors can be
considered "helper molecules" that assist in
biochemicaltransformations. The rates at which these happen are
characterized byenzyme kinetics.

14. ISOENZYMES;
•These are oligomericforms of more than one type of subunits,
synthesized from different gene s but perform similar functions on
the same substrate which is most often located in different
organelles.
A good example of an isoenzymeis lactate dehydrogenase which
catalyzes the interconversion of pyruvate and lactic acid.