Mammalian peroxiredoxin class 6 (Prdx6) are bifunctional enzymes. Non-mammalian Prdx6 enzymes display Cys-based peroxidase activity， but to date their putative phospholipase A₂ (PLA₂ activities) has not been experimentally investigated. Initially， we observed that five non-mammalian Prdx6 enzymes (enzymes from (AtPER1)， (TaPER1)， (PaLsfA) and (AfPrx1 and AfPrxC)) present features compatible with PLA₂ activities in mammalian Prdx6 by amino acid sequences alignment and tertiary structure modeling. Employing unilamellar liposomes with tracer amounts of [³H]-1，2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and thin layer chromatography， all the tested non-mammalian Prdx6 enzymes displayed P... More
Mammalian peroxiredoxin class 6 (Prdx6) are bifunctional enzymes. Non-mammalian Prdx6 enzymes display Cys-based peroxidase activity， but to date their putative phospholipase A₂ (PLA₂ activities) has not been experimentally investigated. Initially， we observed that five non-mammalian Prdx6 enzymes (enzymes from (AtPER1)， (TaPER1)， (PaLsfA) and (AfPrx1 and AfPrxC)) present features compatible with PLA₂ activities in mammalian Prdx6 by amino acid sequences alignment and tertiary structure modeling. Employing unilamellar liposomes with tracer amounts of [³H]-1，2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and thin layer chromatography， all the tested non-mammalian Prdx6 enzymes displayed PLA₂ activities， with values ranging from 3.4 to 6.1 nmol/min/mg protein. It was previously shown that Thr177 phosphorylation of human Prdx6 increases its PLA₂ activity， especially at neutral pH. Therefore， we investigated if human Erk2 kinase could also phosphorylate homologous Thr residues in non-mammalian Prdx6 proteins. We observed phosphorylation of the conserved Thr in three out of the five non-mammalian Prdx enzymes by mass spectrometry. In the case of the mitochondrial Prdx6 from (AfPrxC)， we also observed phosphorylation by western blot， and as a consequence， the PLA₂ activity was increased in acidic and neutral conditions by the human Erk2 kinase treatment. The possible physiological meanings of these PLA₂ activities described open new fields for future research.
