This document categorizes enzymes into six main classes based on their catalytic activity: 1) Oxidoreductases catalyze redox reactions such as dehydrogenation and oxidation. 2) Transferases transfer atomic groups between molecules, like transaminases transferring amino groups. 3) Hydrolases catalyze hydrolysis reactions by adding water, as seen in maltase breaking maltose into glucose. 4) Lyases break chemical bonds without water, such as decarboxylases removing carboxyl groups. 5) Isomerases catalyze conversion between isomers by moving atomic groups. 6) Ligases catalyze bond formation using ATP, for example DNA ligase in DNA synthesis.

1. 1. Oxidoreductases
• are involved in redox reactions
• Eg.
Dehydrogenase (removal of hydrogen)
Oxidase (add oxygen to hydrogen ,forming water)

2. 2. Transferases
• They transfer a group of atoms
form one molecule to another
• General equation :
A-X + B ↔ BX + A
• Eg. :
transaminase (transfer amino
group from one molecule to
another)
phosphotransferase ( transfer
of phosphate group)

3. 3. Hydrolases
• catalyze hydrolysis of substrate by addition of
water
• General equation :A-X + H2
O ↔ X-OH + HA
• Eg. :
maltase ( maltose broken to 2 glucose)
lipase (lipid broken to fatty acid and glycerol)

4. 4. Lyases
• breaks chemical bonds without adding water
• General equation : A-B → A=B + X-Y
• Eg.,
decarboxylases ( remove carboxyl group from
respiratory substrates to release carbon
dioxide)

5. 5. Isomerases
• catalyzes conversion of one isomer to
another by transferring a group of atoms from
one molecule to another

6. 6. Ligases
• catalyzes the synthesis of new chemical bonds,
using ATP
• Eg.,
DNA ligase is involved in DNA synthesis

7. 6. Ligases
• catalyzes the synthesis of new chemical bonds,
using ATP
• Eg.,
DNA ligase is involved in DNA synthesis