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Biochemical and ecological characterization of two peroxidase isoenzymes from the mangrove, Rhizophora mangle
Author(s) -
PEARSE IAN S.,
HEATH KATY D.,
CHEESEMAN JOHN M.
Publication year - 2005
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2005.01307.x
Subject(s) - rhizophora mangle , peroxidase , caffeic acid , rutin , botany , gallic acid , coniferyl alcohol , chlorogenic acid , quercetin , biology , chemistry , mangrove , biochemistry , lignin , antioxidant , enzyme , ecology
This study examines phenolic peroxidase (POX) in Rhizophora mangle L. leaves in order to assess its role in phenolic manipulation and H 2 O 2 scavenging. Sun‐exposed and understorey leaves experiencing varying degrees of nutrient stress were analysed from an oligotrophic cay off the coast of Belize. POX activity was unaffected by growth environment, but increased throughout leaf development and persisted through senescence and after abscission. Histochemical analyses indicated POX activity throughout leaf tissues, especially in the apoplast. Phenolics were similarly broadly distributed. Two isoenzymes of POX were partially characterized with pIs of 4.1 and 6.3 and masses of 65.5 and 54.3 kDa, respectively. The larger, more acidic isoenzyme showed especially high heat stability, showing no reduced activity after 24 h at 60 °C. Rhizophora mangle POX oxidized quercetin preferentially, and, to a lesser extent, coniferyl alcohol, caffeic acid, chlorogenic acid, and p ‐coumaric acid. It did not oxidize ascorbate, but ascorbate could act as a secondary electron donor in the presence of a phenolic substrate and H 2 O 2 . However, because quercetin and other aglycones were not present in R. mangle leaves, and because POX showed no activity with the most abundant leaf flavonoid, rutin, it was concluded that detoxification of H 2 O 2 is secondary to the other roles of POX in manipulation of phenolics.