STM Article Repository

Aims: In this study, paraoxonase (PON) enzyme was purified from mature seeds of sun flower by using affinity chromatography (Sepharose-4B-L-tyrosine-1-naphthylamine) and the effects of some chemicals were tested on paraoxonase activity as in vitro.
Methodology: Paraoxonase was firstly purified from sun flower (Helianthus annuus). This enzyme was purified as 427-fold. SDS-polyacrylamide electrophoresis of the enzyme indicates a single protein staining band with an apparent Mr of 35 kDa. The kinetic properties of the purified enzyme were determined.
Results: The enzyme exhibits high activity at broad pH (pH 5.0-9.0) and temperature (40 and 70ºC). The purified enzyme remains stable at 4ºC for more than 1 year. Paraoxonase is mostly stable at 40ºC. The activity of the enzyme decreases to 55% at a temperature of 60ºC when the treatment was given for a period of 1h. Optimum pH of the purified enzyme was 7.0 and its optimum temperature was 40ºC. Using paraoxon as a substrate, the enzyme shows maximum activity (Vmax) of 7.84μmol.L.min-1 with its corresponding Km value of 0.317 mM. The activities was strongly inhibited by Hg2+, Fe3+, β-mercaptoethanol, dithioerythritol, SDS and EDTA while Cu2+ slightly activates the enzyme activity. As judged by catalytic efficiencies, paraoxon is the preferred substrate.
Conclusion: The present study shows that PON purified from sun flower (Helianthus annuus) is stable at wide range of pH and temperature and in the presence of some metal ions.