Isolation and a Study of Acidic Deoxyribonuclease from Blood of Acute Myocardial Infarction Patients

The current research was concerned with a biochemical study of acidic deoxyribonuclease DNase II which was isolated from the serum of patients suffering acute myocardial infarction (AMI) as a marker for diagnosis of AMI. The results showed a significant increase in the activity of DNase II enzyme in the serum of the AMI patients with a mean value (268.0+ 6.90) U/L compared to the activity of healthy people (25.7+ 1.60) U/L. The enzyme was isolated from the blood of AMI patients using different biochemical techniques. Two proteinous components had been isolated by gel filtration technique from the precipitate produced by ammonium sulfate. It was found that only the first peak has DNase II activity. The apparent molecular weight of the enzyme using gel filtration was found to be (67000) Dalton. The research was also concerned with finding of optimum conditions for DNase II activity. Maximum activity was obtained using (32) g/ ml of deoxyribonucleic acid as a substrate for the enzyme, in acetate buffer at pH (4.50) and temperature of (40) 0C at a reaction time of (150) second. Using Line Weaver-Burk plot, it was found that maximum velocity Vmax and Michaelis Menten constant Km have the values of (120.5) U/ L and (1.8) g / ml respectively. Finally, the effect of some chemical compounds and nucleotides on the DNase II activity was also studied. It was found that EDTA showed a maximum inhibition with (100%) on the activity of the enzyme at a concentration of (5) mmol, while CuSO4 obtained maximum activation with (157.36%) on the activity of the enzyme at a concentration of (10) mmol in comparison to other chemical compounds, But. -Mercaptoethanol, 5'-dGMP and 5'-dUMP showed activation effect on the activity of the enzyme at a concentration (0.1) mmol with (78.02%, 189% and 201%) respectively. It was found that Isordil showed a competitive inhibition on the activity of the enzyme at a concentration of (0.01) M.