Optimization of extraction and biochemical characterization of soluble and ionically wall-bound peroxidases from Argania spinosa leaves

Peroxidases (POX) play key roles in plant stress responses and metabolism. However, their extraction and functional properties in Argania spinosa leaves remain underexplored. In this study, soluble and ionically wall-bound peroxidases were extracted and assayed using guaiacol and H2O2 as substrates. Active peroxidases were recovered only in the presence of phenol-complexing agents (PVP and PVPP), highlighting the strong inhibitory effect of endogenous polyphenols. The soluble fraction exhibited optimal activity at pH 5.6 and temperatures up to 55 °C. In contrast, the ionically wall-bound fraction was active over a broader pH range (3.4–9.0), with maximal activity at pH 5.0 and 55 °C, and remained stable at elevated temperatures up to 90 °C. Metal ions (Ca2+, Mg2+, and Fe2+) enhanced peroxidase activity, with Fe2+ and Cu2+ abolishing the lag time in guaiacol oxidation. These results underline the remarkable stability of wall-bound peroxidases from A. spinosa leaves and support their potential relevance for industrial and biotechnological applications, as well as for plant stress tolerance mechanisms.