Unique properties of arginase purified from camel liver cytosol

Abstract

Arginase (ARG) is an enzyme involved in urea cycle, where it catalyzes the hydrolysis of L-arginine into L-ornithine and urea. Since there is no information about the isolation and purification of ARG from camel liver, this investigation was designed to purify and characterize ARG from camel liver and compare its molecular and kinetic properties with that reported from other species. Camel liver arginase (CL-ARG) was purified to homogeneity using heat denaturation followed by ammonium sulphate precipitation with a combination of DEAE-cellulose, SP-Sepharose and Sephadex G 100-120 chromatography columns. The specific activity of CL-ARG was increased to 18,485 units/mg proteins with 23.5-fold purification over crude homogenate. It was observed that CL-ARG showed a similarity with other species such as behaviour on DEAE-cellulose column, kinetics of inhibition, necessity for metal ions as cofactor, and alkaline optimum pH. On the contrary, CL-ARG differed in its molecular weight (180 kDa), oligomeric protein structure, slightly neutral-alkaline pI value (7.7), Km value (7.1 mM), optimum pH (9, 10.7), and higher optimum temperature (70 °C). In conclusion, this study investigated the properties of CL-ARG via a simple and reproducible purification procedure and provided valuable information for its production from available source in Egypt for medical and industrial purposes.