1.2 Classification
of Enzyme
The commission of
enzymology decided the nomenclature and the classification of enzymes according
to the direction of international union of Biochemistry (IUB) in 1961. This
makes them group enzymes into six broad groups which include oxido-reductase –
catalyzed oxidation and reduction reaction; Transferases – They catalyse the
transfer of group from one molecule to another molecule. Hydrolases – They
catalyse the hydrolysis of substance by addition of water molecule across the
test for normal of deficiency of the blood samples collected.
Bond Lyase – Also
catalyse the addition or removal of group from the substrate without
hydrolysis.
Isomerases – catalyse the
conversion of a compound into an isomer, and thus Ligases – They catalyse
Linking together of molecules coupled with the breaking of pyrophosphate bond
in ATP.
International Classification of an enzyme
|
Number
|
Classes
|
Types of reaction catalysed
|
|
1
2
3
4
5
6
|
Isomerases
Ligases
Lyases
Oxidoreductase
Transferases
Hydrolases
|
Transfer of groups
within molecules to yield isomeric form.
Formation fo C – C, C –
S, C – O and C – N bonds by condensation reactions coupled to ATP cleavage.
Addition of groups to
double bonds or formation of double bonds by removal of groups.
Transfer of electrons
(hydrides ion or H)
Group transfer
reactions
Hydrolysis reaction
(transfer of functional groups to
water).
|
Adapted from Lehninger
(Fourth Edition)
1.3 Glucose-6-Phosphate
Dehydrogenase Enzyme
G-6-PD belongs to the
group of oxido-reductases because it catalyses the removal of hydrogen (H) from
substrate by oxidation
SH2 Enzyme S + 2H
Oxidase
Another example where
G-6-PD exhibit an absolute specificity for substrate is where it removed two
electrons and two protons from glucose-6-phosphate to yield phosphoglucose acid
Lactone
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