as all enzymes within the plant peroxidase superfamily, and in
the parallel peroxidase-cyclooxygenase superfamily
[56], which was previously named as mammalian hemecontaining
peroxidase family. Very recently, a third
heme-containing, so called dye-peroxidase (DyP) enzyme
family was recognised with abundant putative
and cloned genes from fungi and bacteria [57]. Novel
nomenclature and grouping is established in the PeroxiBase
database (http://peroxibase.toulouse.inra.fr/)
[58]. PeroxiBase includes also non-heme peroxidases,
and interlinks with nucleotide sequence and protein
structure accessions in other databases.
For all heme peroxidases, H2O2 or organic peroxides
act as the primary catalyst (oxidant), and two electrons
are derived from substrate molecules in order to gradually
reduce the enzyme (via Compound I and Compound
II intermediates) back to the resting stage with
concomitant release of two water molecules [54] (see
Scheme 1). The reactions catalysed by plant peroxidase
superfamily enzymes generally yield organic radicals
(A