Abstract : Arginase enzyme produced and purified from Pseudomonas aeruginosa by four steps, ammonium sulphate, dialysis, ion exchange and gel filtration and purified L-arginase showed the maximum activity at pH 8.0 in the presence of Mn2+ ions and the enzyme activity was increased significantly by the addition of ZnSO4, MgCl2, and MnCl2 ions separately in the enzymatic reaction mixture, and inhibited potently by chemicals such as (CuCl2 and EDTA).