Enzymes

Question 1

Reaction and Example of: Oxidoreductases

Answer 1

Catalyse redox reaction
Or
Transfer of electrons

AH + B → A + BH(reduced)
A + O → AO(oxidised)
Or
A- + B → A + B-

Examples:
- catalase
- cytochrome oxidase
- lactate dehydrogenase
- peroxydases
- alcohol dehydrogenase

Question 2

Reaction and Example of: Transferases

Answer 2

Catalyse transfer of a molecular group such as: an amino group, acetyl group, or phosphate group from one molecule to another
Or
Transfer of C-, N- or P- containing groups

AB + C → A + BC

Examples:
- acetate kinase
- alanine aminotransferase
- aspartate transaminase
- hexokinase
- creatine kinase

Question 3

Reaction and Example of: Hydrolases

Answer 3

Catalyse bond cleavage by the introduction of water
Or
Bond cleavage by addition of water

AB + H2O → AOH + BH

Examples:
- lipase
- alpha-amylase
- peptidases
- sucrases
- urease
- alkaline phosphatase
- trypsin
- invertase
- urease
- alkaline phosphatase

Question 4

Reaction and Example of: Lysases

Answer 4

Catalyse non-hydrolytic addition or removal of groups from substrates. C-C, C-N, C-O or C-S bonds may be cleaved
Or
Cleavage of C-C, C-S and C-N bonds often to form a double bond

RCOCOOH → RCOH + CO2
Or
[X-A-B-Y] → [A=B+X-Y]

Examples:
- oxalate decarboxylase
- isocitrate lyase
- pyruvate decarboxylase

Question 5

Reaction and Example of: Isomerases

Answer 5

Catalyse reactions involving rearrangements of atoms within a molecule
Or
Formation of optical or geometric isomers

AB → BA

Examples:
- glucose-6-phosphate isomerase
- alanine racemase
- maleate isomerase

Question 6

Reaction and Example of: Ligases/Synthases

Answer 6

Catalyse reactions joining together two molecules, most often by synthesis of new C-O, C-S, C-N or C-C bonds with simultaneous breakdown of ATP
Or
Hydrolysis of high energy phosphates to form new bonds

X + Y + ATP → XY + ADP + Pi
Or
A + B → AB

Examples:
- acetyl-CoA synthetase
- DNA ligase
- pyruvate carboxylase