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Proline is a quencher of singlet oxygen and superoxide both in in vitro systems and isolated thylakoids
Author(s) -
Rehman Ateeq Ur,
Bashir Faiza,
Ayaydin Ferhan,
Kóta Zoltán,
Páli Tibor,
Vass Imre
Publication year - 2021
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.13265
Subject(s) - singlet oxygen , superoxide , thylakoid , reactive oxygen species , chemistry , photochemistry , proline , oxygen , hydrogen peroxide , paraquat , quenching (fluorescence) , hydroxyl radical , radical , spin trapping , electron paramagnetic resonance , biophysics , biochemistry , fluorescence , chloroplast , organic chemistry , nuclear magnetic resonance , biology , amino acid , physics , quantum mechanics , gene , enzyme
Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6‐tetramethyl‐4‐piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro. By comparing the effects of chemical scavengers and physical quenchers, we concluded that proline eliminates singlet oxygen via a physical mechanism, with a bimolecular quenching rate of ca. 1.5–4 10 6 M −1 s −1 . Our data also show that proline can eliminate superoxide in vitro in a process that is likely to proceed via an electron transfer reaction. We could also show that proline does quench both singlet oxygen and superoxide produced in isolated thylakoids. The scavenging efficiency of proline is relatively small on a molar basis, but considering its presence in high amounts in plant cells under stress conditions it may provide a physiologically relevant contribution to ROS scavenging, supplementing other nonenzymatic ROS scavengers of plant cells.