Biomolecules-Enzymes | UK-Sir-Notes | Biomolecule-4
ENZYMES:
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| Enzyme Substrate |
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Definition:
Ø Enzyme
is also called as bio catalyst.
Ø Anselme
Payen (1833)- discovered enzyme.
Ø Buchner
(1897)- isolated 1st enzyme
from yeast reaction- called as Zymase.
Ø Louise
Pasteur (1860)-coined the term ferments
Ø Kuhne
(1878)-coined the term enzyme.
Ø Several
thousand number of enzymes present with in a body.
Ø All
enzymes are protein biocatalyst.
Ø Enzymes
are those which can catalyze the biological reactions inside body or cell with
out any change of them.
Ø If
present outside cell- exoenzyme (digestive juice)
Ø If
present inside cell- endoenzyme (enzymes of glycolysis)
Ø Act
on the substance called as substrate.
CHEMICAL NATURE:
Ø Almost
enzymes are Globular proteins.
Ø They
may be of 2 types:
Ø Simple
enzymes: totally made by protein, active site formed by own A.A.
(Ex- Pepsin, urease etc)
Ø Conjugated
Enzymes: made by two part,
Protein part (apoenzyme) +
non protein part (cofactor) = Holoenzyme (active form)
Cofactor may be – Coenzyme
and prosthetic group.
Coenzyme- separable
organic co factor (coenzyme A, ATP, NADP+)
Prosthetic Group- tightly
attached (Heme group, FMN, FAD etc)
There is also presence of
some metal activaters (Inorganic cofactors)-Fe 2+ for catalase, Cl-
for Salivery Amylase.
 |
| Complete enzyme |
Active
Site:
Ø Part
of enzyme which perform the function- named as active site.
Ø Active
spot may be – one or several.
They have Specific charge,
size and shape to hold substrate.
NOMENCLATURE AND CLASSIFICATION:
Ø Common
Suffix – ase (few exception)
Ø Mostly
name given after-
Type
of Substrate: Sucrase, lipase, Nuclease etc
Type
of Reaction: dehydrogenase, oxidase etc
Classification by International Union Of Biochemistry (IUB) 1961: 6 categories.
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| Enzyme Classification |
ACTIVATION Energy:
Ø It
is the amount of energy need to over come the energy barrier for start of the
reaction.
Ø 
Every reaction can’t start
itself- due to mutual repulsion, hydrogen bonding, small reactant site etc.
Ø Activation energy is always external.
 |
| Activation energy |
MODE OF ENZYME ACTION:
There
are 2 hypothesis:
1.
Lock and Key Hypothesis:
Ø By
Emil Fischer (1894)
Ø Substrate
and enzyme have specific geometrical shape like one lock and key.
Ø Every
lock have specific key, like wise every Enzyme have specific substrate.
 |
| Lock and key hypohesis |
2. Induce Fit Theory:
Ø By
Koshland (1959)
Ø Active
sites are not fixed, rather they can change their configuration.(conformational
change)
Ø
Active site contain two
groups- buttressing (support the substrate) and catalytic group (weakens the
bonds of reactant)
 |
| Induce fit theory |
PROPERTIES OF ENZYMES:
Ø All
enzymes are proteins, mostly globular protein, few are Ribozyme.
Ø Most
of the enzymes are colloidal in nature.
Ø They
increase the rate of chemical reaction.
Ø Enzymes
are highly specific- for substrate.
Ø They
are also Heat sensitive- Optimal temp is 15-350 (after 550 denatures)
Ø They
are Specific to pH.
Ø Theymay
perform chain ractions.
TYPE OF ENZYMES:
Proenzymes or Zymogen:
Ø These
are Precursor of enzyme – in inactive form
Ø Become
reactive or activate at specific pH.
Ø Ex
- Pepsinogen convert to Pepsin in gastric juice
Allosteric Enzyme:
Ø That
enzyme which contain different allosteric sites for different modulators or
effectors.
Ø Like-
activator , inhibitors
Isoenzymes or Isozymes:
Ø Isozymes
are number of variants of a specifc enzyme.
Ø They
can perform the same substrate activity,
same function and can give same product.
Ø More
then 100 enzymes have isozymes.
Ø Ex-Lactic
dehydrogenase have 5 isozymes
Enzyme Function Velocity:
 |
| Km |
 |
| Equation |
Inhibition Of Enzyme action:
 |
| Inhibition |
 |
| Inhibition type |
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| Type of Inhibition 4 |
Want to Know about Amino acids, Proteins:
Want to Know about Carbohydrates :
https://uksirnotes.blogspot.com/2021/09/Biomolecules-Carbohydrates-uksir.html
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