This document summarizes the chemistry of enzymes, including their classification and chemical composition. It discusses that enzymes are proteins that act as biological catalysts and speed up reactions. Enzymes are classified in multiple ways, including based on their site of action as intracellular endoenzymes or extracellular exoenzymes, and based on the reaction they control using the EC system of six main classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. The document also describes several key enzyme terminology concepts, such as cofactors, coenzymes, prosthetic groups, and substrates.

1. The Chemistry of Enzyme, Classification and
Chemical Composition
Presented by :Birtucan D, Yirga and
November /2019
Bahirdar ,Ethiopia

2. Out Line
• 1.what is Enzyme
1.1 Terminologies
1.2 Chemical Nature of Enzyme
• 2 Classification of Enzyme

3. 1.What are enzymes?
• Are bio- catalyst that speed up biological reaction.
• All are protein except ribozymes(RNA)
• They are specific in their action
• Have active site

4. 1.1 Terminologies
Co-enzyme :non protein organic substance attached to the
protein part.
Prosthetic group :inorganic substance(cofactor) attached to
apoenzyme of protein
Metal -ion activator: K+, Fe++,cu+++,Zn++,Mg++,Ca++
Substrate :reactant in biological reaction bind with enzyme

5. Terminologies
Holoenzyme :Apoenzyme +cofactor
Co factors- non protein molecule which carries out chemical
reactions.
Ribozymes :RNA species that act as enzyme

6. 1.2 Chemical Nature of Enzyme
• Occur in combination with cofactors
• Polypeptide fold amino acids to form active site
• Inactive with out cofactors (co enzyme, prosthetic group or
metal-ion activator)

7. Chemical Nature of Enzyme
It has two parts
 The first part is the substrate
 The second is the reaction with suffix “ase “
 They did not consumed in the process
 Made of chain of amino acid

8. 2.Classification of Enzyme
2.1 Based on site of Action
endoenzyme (intracellular)
 act inside the cell
 Responsible for synthesis of cell
components, production of energy,
metabolism
 E.g. Synthetase , isomerase
Exo enzyme(extracellular)
 act outside the cell
 digestive in their function
 Breakdown complex molecule
 E.g. proteases ,amylases
• 2.2 Based on Nature of
Substrate
• Carbohydrates
• The esterase
• The Photolytic enzyme
• The oxidizing enzyme….

9. 2.3 Classification and Chemical Composition
of Enzyme Based on Reaction They Control
There are six group of enzymes
developed by international union of biochemistry and
molecular biology
 based on the reaction they catalyze(enzyme
commission number)
 EC specify the enzyme catalyzed reaction not the
enzyme.

10. i. EC1 - Oxidoreductase
Catalyzed the transfer of hydrogen or oxygen electrons.
Electron donor/acceptor is required to complete the reaction.
Require adenine dinucleotides (NAD,NADH) & Flavin(FAD,FADH2).
 Catalyze oxidation and reduction reaction
The substrate ,considered as hydrogen donor
reduced substrate oxidized coenzyme oxidized product reduced coenzyme

11. ii. EC2 - Transferase
Catalyze the transfer of a functional group between two
substrates.
The group can be methyl-,acyl- .or phosphate group
AB +CA +BC
E.g. transaminase and kinase

12. iii. EC3 - Hydrolase
 Catalyze Hydrolytic reaction of carbohydrates, esters and
proteins(esterase ,peptidases, lipases)
 There is formation of two products
 AB +H20---AOH +BH
amide  acid + ammonia

13. iv. EC4 - Lyase
Catalyzes the removal of groups from substrates by means of
other than hydrolysis.
There is formation of double bond in the product
Include decarboxylases and aldolases in the removal direction,
and synthases in the addition direction
RCOCOOH  RCOH + CO2

14. v. EC5 - Isomerase
Catalyze the interconversion of Cis-trans isomers(intracellular
arrangement)
Change with in same molecule
ABC ----BCA
Isomerase and mutase

15. vi. EC6 - Ligase
Catalyzes the Synthesis of various new bonds.
Catalyzes the coupling of two compounds with breaking of
pyrophosphate bonds usually ATP.
X +Y +ATPXY +ADP +Pi

16. Thank you!!!