Characterization of a recombinant arginine deiminase from Enterococcus faecalis SK32.001 for L-citrulline production

Arginine deiminase is an enzyme used to biosynthesize L-citrulline from L-arginine. The arginine deiminase gene of Enterococcus faecalis SK32.001 was expressed in Escherichia coli with a specific activity of 131.2 U mg(-1). The expressed enzyme was a dimer with a subunit molecular weight of 49.1 kDa. It was stable in a pH range of 5.0-5.5 and in a temperature range of 20 degrees C to 25 degrees C. The optimum pH and temperature of the enzyme were 5.5 and 55 degrees C, respectively. Fe3+ enhanced its enzymatic activity. The chemical modifiers and the three-dimensional structural model of the recombinant enzyme indicated that Lys, Trp and Cys were very important amino acid residues to the enzyme. It's K-m and V-max for L-arginine were 10.1 mM and 378.1 mu mol min(-1) mg(-1), respectively. The bioproductions of L-citrulline with the resting recombinant cells at 30 degrees C and 45 degrees C were 97.4 g L-1 and 96.9 g L-1, respectively.