Hydrogen peroxide content and vanadium-dependent haloperoxidase activity in thalli of six species of Fucales (Phaeophyceae)
2015
Tarakhovskaya, Elena R. | Bilova, Tatiana E. | Maslov, Yuri I.
Patterns of hydrogen peroxide content and vanadium-dependent haloperoxidase (V-HPO) activity were investigated in thalli of six species of Fucales (Fucus vesiculosus, F. serratus, F. edentatus, F. distichus, Ascophyllum nodosum and Pelvetia canaliculata). H₂O₂ levels in all species were similar to those of photosynthesizing tissues of unstressed terrestrial plants. The highest H₂O₂ content (up to 0.7 μM g FW⁻¹) was in F. distichus and Pelvetia. H₂O₂ content in the basal and middle zones of fronds was generally higher than in vegetative apices and receptacles. Similar trends were detected for V-HPO activity with both bromide and iodide. Intrathallus profiles of H₂O₂ content and V-HPO activity may be attributed to the physiological condition of the respective thallus zones, i.e. photosynthetic activity and stage of cell differentiation. Steady-state kinetics showed significant variation of V-HPO parameters between fucoid species, suggesting that they contain different forms of the enzyme. V-HPO from high-intertidal Pelvetia and F. distichus exhibited the highest Kₘ values for both halide and H₂O₂. The enzyme form with the maximum kinetic efficiency occurred in the mid-intertidal fucoids. For all investigated species, the iodination activities were two to four times lower than for bromination. Apparently, V-HPOs contribute significantly to the control of reactive oxygen species accumulation in Fucales. The similarity of the longitudinal profiles of H₂O₂ content and peroxidase activity between Fucales and terrestrial plants suggests a physiological analogy of V-HPO and secretory peroxidases.
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