Due to the fact that – in contrast to monooxygenases – no external nicotinamide
cofactor is required in the peroxidase cycles, peroxidases are highly attractive for
preparative biotransformations. A number of synthetically useful reactions can be
achieved (Scheme 2.172) [1463–1465]. Depending on the enzyme–substrate combination, the replacement of hydrogen peroxide by tert-butyl hydroperoxide may be
beneficial.
Oxidative Coupling
This reaction is commonly denoted as the ‘classical’ peroxidase activity, since it
was the first type of peroxidase-reaction discovered.
It is mainly restricted to heme peroxidases and it involves the one-electron
oxidation of phenols (e.g., guaiacol, resorcinol) and anilines (e.g., aniline, oHis
Fe 3+
SubO
Sub
+ H 2 O
Sub •
SubH
Compound II
Compound I
•
+
H 2 O
H 2 O 2
N
N
N
N
His
Fe
4+
N
N
N
N
O
His
Fe 4+
N
N
N
N
OH
- e
- e
peroxygenase-path
Sub •
SubH
peroxidase-path
Scheme 2.171 Catalytic cycles of heme-dependent peroxidases
SubO + H 2 O
Sub + H 2 O 2
Sub—Sub
2 Sub • + 2 H 2 O
2 SubH + H 2 O 2
Oxygen transfer (peroxygenase-path)
Oxidative halogenation (peroxidase-path)
Oxidative coupling (peroxidase-path)
SubH + H 2 O 2 + Hal
- + H
+
Sub-Hal + 2 H 2 O
Scheme 2.172 Synthetically useful peroxidase and peroxygenase reactions
200
2 Biocatalytic Applications