Purification of holstein bull semen paraoxonase 1 (pon1) by hydrophobic interaction chromatography and investigation of its inhibition kinetics by heavy metals
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In this study, paraoxonase 1 (PON1; EC 184.108.40.206) was purified from bull semen, and some characteristics of the enzyme were investigated. In vitro inhibition effect of some heavy metals, including Cu2+, Mn2+, Cd2+, Zn2+, Ni2+, and Pb2+, on the activity of the purified enzyme was also investigated. The purification of bull semen PON1 procedure was composed of two steps: ammonium sulfate precipitation and Sepharose-4B-l-tyrosine-1-naphthylamine hydrophobic interaction chromatography. The enzyme, having a specific activity of 288 EU/mg proteins, was purified 22.67-fold with a yield of 89 %. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the purified enzyme showed the presence of a single band with an apparent MW of 66 kDa. The V (max) and K (M) values for the paraoxon substrate were determined as 100 EU and 8.0 x 10(-5) M, respectively. The inhibitory effects of different heavy metals on PON1 activity were determined by using the paraoxon as a substrate. The results showed that all the metals, except for Cd2+, inhibited the PON1 enzyme activity in a concentration-dependent fashion. IC50 values of Cu2+, Mn2+, Zn2+, Ni2+, and Pb2+ were found as 2.59 x 10(-3), 1.17 x 10(-3), 42.74 x 10(-3), 99.10 x 10(-3), 48.80 x 10(-3) mM, respectively. Conversely, Cd2+ increased the bull semen PON1 enzyme activity. The present study has demonstrated that Cu2+, Mn2+, Zn2+, Ni2+, and Pb2+ are serious toxic metals, which are able to increase the risk of oxidative stress development and a subsequent decrease of semen quality.