Extraction and purification of bovine pancreatic Deoxyribonuclease I

Abstract

Samples of bovine pancreatic and calf thymus glands were collected from local slaughterers to extract deoxyribonuclease I enzyme (DNase I) and DNA respectively. Crude extract was prepared by using cooled distilled water and 0.25 N sulfuric acid .This study show that the best condition for the crude extract activity was 17 U/ml and 1 hr. Incubated period reaction with its substrate.The bovine pancreatic DNase I was purified by several steps of precipitation using ammonium sulphate to 529.4 times, with an enzymes yield 6.35%. Enzyme characterization studies indicate that: it is active at 2.7 U/ml, and 50 µg /ml DNA after 30 min of reaction time, the enzyme activity was higher at pH 6.5 and it showed stability at pH 9. The maximum enzyme activity was reported at 50 °C The results obtained from the role of metal ions (Mg+2, Mn+2) on enzyme activity indicate that these ions stimulated the enzyme activity while the Ca+2 and Cu+2 had lower stimulating activity on the enzyme but Ag+1 and Hg+2 showed inhibitory effect on enzyme activity. In addition the enzyme activity was inhibited by using denaturing Sodium dodecyl sulphate (SDS), chelating agents Ethylene diamine tetra acetic acid (EDTA), and reducing agents (2-Merceptoethanol and Urea) , and maintained it's activity when incubated with Phenyl Methyl Sulphonyl Floride (PMSF) .