Purification and Characterization of Arginine Kinase from Locust

Abstract

L-Arginine kinase (AK; ATP:L-arginine N-phosphotransferase; EC 2.7.3.3) catalyzes the reversible transphosphorylation between N-phospho-L-arginine (PArg) and ATP thus buffering cellular ATP levels. AK was purified from the leg muscle of the locust Migratoria manilensis by Sephacryl S-200 HR gel filtration chromatography and DEAE Sepharose CL-6B fast flow anion exchange chromatography to an apparent homogeneity with a recovery of 80%. The enzyme behaved as monomeric protein with molecular mass of about 40 kD, and had a pH and temperature optimum of 8.6 and 30 degrees C, respectively, and a pI of about 6.3. The Michaelis constants for synthesis of PArg are 0.936 and 1.290 mM for L-arginine and ATP, respectively and k(cat)/K(m)(Arg) 174. The activity of AK required divalent cations such as Mg(2+) and Mn(2+). In the presence of Cu(2+) and Zn(2+), AK activity was greatly inhibited. The intrinsic protein fluorescence emission maximum at 330 nm using the excitation wavelength at 295 nm suggested that tryptophan residues are below the surface of the protein and not exposed to solvent.