3. Enzymes are classified by the reactions they catalyze 3.1 Trivial names are usually given to enzymes. 3.1.1 Many enzymes have been named by adding the suffix“-ase” to the name of their substrate or to a word or phrase describing their activity(type of reaction). 3.2 Enzymes are categorized into six major classes by international agreement 3.2.1 The six major classes include Oxidoreductases: catalyzing oxidation-reduction reactions Transferases: catalyzing the transfer of a molecular group from one molecule to another
3. Enzymes are classified by the reactions they catalyze 3.1 Trivial names are usually given to enzymes. 3.1.1 Many enzymes have been named by adding the suffix “-ase” to the name of their substrate or to a word or phrase describing their activity (type of reaction). 3.2 Enzymes are categorized into six major classes by international agreement. 3.2.1 The six major classes include Oxidoreductases: catalyzing oxidation-reduction reactions. Transferases: catalyzing the transfer of a molecular group from one molecule to another
3.2.1(contd) Hydrolases: catalyzing the cleavage by the introduction of water. bases: catalyzing reactions involving removal of a group to form a double bond or addition of groups to double bonds. (eg.2) somerase: catalyzing reactions nvolving intramolecular rearrangements Ligases: catalyzing reactions joining together two molecules
3.2.1 (cont’d) Hydrolases: catalyzing the cleavage by the introduction of water. Lyases: catalyzing reactions involving removal of a group to form a double bond or addition of groups to double bonds. (e.g.?). Isomerases: catalyzing reactions involving intramolecular rearrangements. Ligases: catalyzing reactions joining together two molecules
3.3 Each enzyme is given a systematic name which identifies the reaction catalyzed(e.g, hexokinase is named as ATP glucose phosphotransferase). 3.4 Each enzyme is assigned a four-digit number with the first digit denoting the class it belongs, the other three further clarifications on the reaction catalyzed
3.3 Each enzyme is given a systematic name which identifies the reaction catalyzed (e.g., hexokinase is named as ATP:glucose phosphotrasferase). 3.4 Each enzyme is assigned a four-digit number with the first digit denoting the class it belongs, the other three further clarifications on the reaction catalyzed
table 8-3 International classification of enzymes No Class Type of reaction catalyzed Oxidoreductases Transfer of electrons(hydride ions or H atoms) Transferases 123456 Group-transfer reactions Hydrolases Hydrolysis reactions(transfer of functiona groups to water) Addition of groups to double bonds, or formation of double bonds by removal of groups Isomerases Transfer of groups within molecules to yield isomeric forms Ligases Formation of C-C, C-S, C-0, and C-N bonds by condensation reactions coupled to ATP cleavage Most enzymes catalyze the transfer of electrons, atoms, or functional groups. They are therefore classified, given code numbers, and assigned names according to the type of transfer reaction. the group donor, and the group acceptor
4. Enzymes, like all other catalysts, does not affect reaction equilibria, only accelerate reactions. 4.1 Equilibrium constant(Kea) eg )of a reaction is related to the free energy difference between the ground states of the substrates and products(△G°) △G°=- STInK q Enzyme catalysis does not affect△G°, thus not eq
4. Enzymes, like all other catalysts, does not affect reaction equilibria, only accelerate reactions. 4.1 Equilibrium constant (Keq’) of a reaction is related to the free energy difference between the ground states of the substrates and products (Go’) Go’ = -RTlnKeq ’ Enzyme catalysis does not affect Go’, thus not Keq’