Lect 3 : Enzymes

Question 1

Enzymes Group I

What do oxidoreductases do? What are the 4 kinds of oxidoreductases?

They

Answer 1

They catalyse redox reactions.
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1. Dehydrogenases : hydride, H^- transfer
2. Oxidases : e^- transfer to molecular oxygen
3. Oxygenases : oxygen transfer from molecular oxygen O₂ to compound
4. Peroxidases : e^- transfer to peroxide, H₂O₂

Question 2

Enzymes Group II

What do transferases do?

Answer 2

They catalyse the transfer of an atom or a group of atoms between 2 molecules.

A + BX –> B + AX

Question 3

Enzymes Group III

What do hydrolases do? Give examples of hydrolases.

Answer 3

Make use of water to hydrolyse chemical bonds.
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A + H₂O –> B + C
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Examples : lipases, proteases, glycosidases

Question 4

Enzymes Group IV

What do lyases do?

Answer 4

Lyases are involved in elimination reactions where a group of atom is removed from substrate (e.g. aldolase, decarboxylase)

**Note: **
- not redox
- no water involved
- Usually generates C=C or a ring

Question 5

Enzymes Group V

What do isomerases do? Give examples?

Answer 5

They catalyse molecular isomerisations
- e.g. epimerase (rmb the -OH group in sugar point up or down, α and β), racemases

Question 6

Enzymes Group VI

What do ligases do?

Answer 6

Catayse te formation of a covalent bond by joining 2 molecules together, coupled with the hydrolysis of ATP (need energy to covalently bond molecules tgt)