16.7.1 Enzymes
These are key agents of biotransformation process. They are known to catalyze
innumerable different chemical reactions. Therefore, these are named and classified
into six classes accordingly by the Nomenclature Committee of the International
Union of Biochemistry and Molecular Biology (NC-IUBMB) (McDonald et al.
2001).
1. Oxidoreductases: Enzymes catalyzing oxidation-reduction reaction, i.e.
oxygenation of C–H, C–C, C¼C bonds, or overall removal or addition of
hydrogen atom equivalents belong to this category.
2. Transferases: Enzymes catalyzing the transfer of a group from one compound to
another belong to this category. The different groups can be a methyl, aldehydic,
ketonic, acyl, sugar, or phosphoryl.
3. Hydrolases: The enzymes which catalyze hydrolytic cleavage of C–O, C–N, C–C
bonds. Hydrolases catalyze the removal of groups from their substrate to acceptor
water molecules.
4. Lyases: These enzymes catalyze the addition or elimination of small molecules on
C¼C, C¼N, C¼O bonds.
5. Isomerases: These enzymes catalyze structural changes like racemization,
epimerization, a rearrangement in a molecule.
6. Ligases: Ligases are enzymes catalyzing the joining together of two molecules
coupled with the hydrolysis of a diphosphate bond in ATP or a similar
triphosphate.
All the above-mentioned enzymes participate in the defined phases of biotransformation. The physical state of these biological agents whether isolated enzyme
systems or intact whole cells varies depending on the following factors (Doelle et al.
2009):
1. The type of reaction.
2. The requirement of co-factors.
3. The scale at which the biotransformation has to be performed.
16.7.2 Immobilized Enzymes
The enzymes restricted to a polymeric matrices or a carrier material by a physical or
chemical treatment form an immobilized enzyme system. Although there is eventual
loss of activity during immobilization of enzymes, these cell-free enzyme systems
are commonly used in biotransformations, due to the following advantages:
1. The single desired product is mostly the end product as undesirable side reactions
do not occur.
2. The desired products are stable and do not degrade.
352
M. H. Yashavarddhan et al.
These are key agents of biotransformation process. They are known to catalyze
innumerable different chemical reactions. Therefore, these are named and classified
into six classes accordingly by the Nomenclature Committee of the International
Union of Biochemistry and Molecular Biology (NC-IUBMB) (McDonald et al.
2001).
1. Oxidoreductases: Enzymes catalyzing oxidation-reduction reaction, i.e.
oxygenation of C–H, C–C, C¼C bonds, or overall removal or addition of
hydrogen atom equivalents belong to this category.
2. Transferases: Enzymes catalyzing the transfer of a group from one compound to
another belong to this category. The different groups can be a methyl, aldehydic,
ketonic, acyl, sugar, or phosphoryl.
3. Hydrolases: The enzymes which catalyze hydrolytic cleavage of C–O, C–N, C–C
bonds. Hydrolases catalyze the removal of groups from their substrate to acceptor
water molecules.
4. Lyases: These enzymes catalyze the addition or elimination of small molecules on
C¼C, C¼N, C¼O bonds.
5. Isomerases: These enzymes catalyze structural changes like racemization,
epimerization, a rearrangement in a molecule.
6. Ligases: Ligases are enzymes catalyzing the joining together of two molecules
coupled with the hydrolysis of a diphosphate bond in ATP or a similar
triphosphate.
All the above-mentioned enzymes participate in the defined phases of biotransformation. The physical state of these biological agents whether isolated enzyme
systems or intact whole cells varies depending on the following factors (Doelle et al.
2009):
1. The type of reaction.
2. The requirement of co-factors.
3. The scale at which the biotransformation has to be performed.
16.7.2 Immobilized Enzymes
The enzymes restricted to a polymeric matrices or a carrier material by a physical or
chemical treatment form an immobilized enzyme system. Although there is eventual
loss of activity during immobilization of enzymes, these cell-free enzyme systems
are commonly used in biotransformations, due to the following advantages:
1. The single desired product is mostly the end product as undesirable side reactions
do not occur.
2. The desired products are stable and do not degrade.
352
M. H. Yashavarddhan et al.