Purification and properties of arginase from human liver and erythrocytes

Abstract

Arginase (EC 3.5.3.1) was isolated from human liver and etythrocytes. The purification procedure used acetone precipitation, heat-treatment, (NH4)2SO4 precipitation, DEAE-cellulose chromatography and gel filtration on Sephadex G-200 in the presence of 2-mercaptoethanol. Both enzymes migrated to the anode at pH 8.3 on polyacrylamide-gel electrophoresis. After incubation at pH 8.0 and 37.degree. C the purified anionic liver arginase migrated to the cathode on polyacrylamide-gel electrophoresis. The multiple forms of the enzyme reported in the literature are probably partly artifacts of the purification procedure. The liver arginase showed a MW of 107,000 determined by gel filtration and a sedimentation coefficient of 5.9S. Treatment of the liver enzyme with 0.25% sodium dodecyl sulphate at pH 10 demonstrated an aligomeric structure of the enzyme with a MW of the subunit of 35,000. The kinetic properties determined for the purified liver arginase showed an optimum pH of 9.3 and an optimal MnCl2 concentration of 2 mM. The Km for L-arginine was 10.5 mM and for L-canavanine 50 mM; L-lysine exhibited a competitive type of inhibition with a Ki of 4.4 mM. L-Homoarginine was not a substrate for liver arginase.