Effect of ammonium sulphate on the activities of paraoxonase isoenzymes Q and R

Abstract

Paraoxonase isoenzymes exists in 2 polymorphic forms, Q (glutamine) or R (arginine) at codon 192. The Q isoform has a higher activity for hydrolyze of diazoxon, sarin and soman; whereas the R isoform has a higher activity for hydrolyze of paraoxon and chlorpyrifosoxon. In this study the effect of ammonium sulphate was investigated on the Q and R isoenzymes. For this purpose, ammonium sulphate precipitation was performed before the Q and R isoenzymes. After ammonium sulphate precipitation the specific activity of R isoform is 20.7 mU/mg. However, after ammonium sulphate precipitation the specific activity of Q isoform is 6.6 mU/mg. After dialysis the specific activity of R isoform is 6.3 mU/mg. However, after ammonium sulphate precipitation the specific activity of Q isoform is 4.8 mU/mg. Q isoenzymes activity did not change significantly as a result of these applications. However, the R isoenzyme activity increased before and decreased in post-dialysis. Ammonium sulfate was found to stimulate the R isoenzyme. This enzyme can use at immobilization and chromatographic procedures; a very important activity is high. If the first step, ammonium sulphate precipitation is performed by selecting the R isoenzyme activity rather increased. Then, the high activity of enzyme can be used easily with other purification methods and immobilization studies.