A novel peroxidase from Ziziphus jujuba fruit: purification, thermodynamics and biochemical characterization properties
Mustafa Zeyadi, Yaaser Q. Almulaiky
Abstract
Abstract In this study, peroxidase from Ziziphus jujuba was purified using ion exchange, and gel filtration chromatography resulting in an 18.9-fold enhancement of activity with a recovery of 20%. The molecular weight of Z. jujuba peroxidase was 56 kDa, as estimated by Sephacryl S-200. The purity was evaluated by SDS, which showed a single prominent band. The optimal activity of the peroxidase was achieved at pH 7.5 and 50 °C. Z. jujuba peroxidase showed catalytic efficiency (Kcat/Km) values of 25 and 43 for guaiacol and H 2 O 2 , respectively. It was completely inactivated when incubated with β-mercaptoethanol for 15 min. Hg 2+ , Zn 2+ , Cd 2+ , and NaN3 (5 mM) were effective peroxidase inhibitors, whereas Cu 2+ and Ca 2+ enhanced the peroxidase activity. The activation energy (Ea) for substrate hydrolysis was 43.89 kJ mol −1 , while the Z value and temperature quotient (Q 10 ) were found to be 17.3 °C and 2, respectively. The half-life of the peroxidase was between 117.46 and 14.15 min. For denaturation of the peroxidase, the activation energy for irreversible inactivation Ea*(d) was 120.9 kJmol −1 . Thermodynamic experiments suggested a non-spontaneous (∆G*d > 0) and endothermic reaction phase. Other thermodynamic parameters of the irreversible inactivation of the purified enzyme, such as ∆H* and ∆S*, were also studied. Based on these results, the purified peroxidase has a potential role in some industrial applications.