Abstract
Plant catalases exhibit spatial and temporal distribution of their activity. Moreover, except from the typical monofunctional catalase, a bifunctional catalase-peroxidase has been reported. The aim of this study was to investigate whether the leaf and root catalases from six different plant species (Lactuca sativa, Cichorium endivia, Apium graveolens, Petroselinum crispum, Lycopersicon esculentum, and Solanum melongena) correspond to the monofunctional or the bifunctional type based on their sensitivity to the inhibitor 3-amino-1,2,4-triazole (3-AT). The leaf catalases from all species seem to be monofunctional since they are very sensitive to 3-AT. On the other hand, the root enzymes from Lactuca sativa, Cichorium endivia, Lycopersicon esculentum, and Solanum melongena seem to be bifunctional catalase-peroxidases, considering that they are relatively insensitive to 3-AT, whereas the catalases from Apium graveolens and Petroselinum crispum display the same monofunctional characteristics as the leaves’ enzymes. The leaf catalase activity is usually higher (Lactuca sativa, Petroselinum crispum, and Solanum melongena) or similar (Cichorium endivia and Apium graveolens) to the root one, except for the enzyme from Lycopersicon esculentum, while in all plant species the leaf protein concentration is significantly higher than the root protein concentration. These results suggest that there are differences between leaf and root catalases—differences that may correspond to their physiological role.
Highlights
A wide range of biotic and abiotic environmental factors induce the generation of ReactiveOxygen Species (ROS) and disturb the redox environment of plant cells leading to oxidative stress [1,2].Hydrogen peroxide (H2 O2 ) is a very common ReactiveOxygen Species (ROS) involved in plant responses, and catalase (CAT) is one of the most important ROS-scavenging enzymes of plants considering that, due to the action of catalases and peroxidases, which decompose this substance, the lifetime of H2 O2 in living tissues is not very long (
We examined the leaf and root CAT activity from different plant species and its sensitivity against 3-AT in order to investigate whether the leaf and root catalases correspond to different types of enzyme
The following plant species were used for this study: Lactuca sativa and Cichorium endivia (Asteraceae), Apium graveolens and Petroselinum crispum (Apiaceae), and Lycopersicon esculentum and Solanum melongena (Solanaceae)
Summary
Catalase was the first discovered and characterized antioxidant enzyme [2] and displays spatial and temporal distribution in plant tissues [4]. The “true” (monofunctional) catalases catalyze a dismutation reaction in which an initial H2 O2 molecule is reduced to H2 O and a second H2 O2 is oxidized to O2 [5]. A second type of the enzyme, mainly found in prokaryotes and some fungi, consists of bifunctional catalase-peroxidases that are structurally distinct proteins and can be distinguished from the monofunctional ones by their relative insensitivity to the inhibitor 3-AT [2]. The bifunctional enzymes, through their peroxidatic activity, can convert H2 O2 to H2 O with the help of a reducing substrate [5]
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