Isolation of Agrobacterium sp. Strain KNK712 That Produces N-Carbamyl-D-Amino Acid Amidohydrolase, Cloning of the Gene for this Enzyme, and Properties of the Enzyme

Abstract

  Agrobacterium sp. strain KNK712, which produced N-carbamyl-D-amino acid amidohydrolase (DCase) was isolated from soil. The bacterium had D-specific hydantoinase activity also. Both enzymes are suitable for use in the production of D-amino acids. The DCase gene from Agrobacterium sp. strain KNK712 was cloned into Escherichia coli. The cloned DNA fragment contained one open reading frame, predicted to encode a peptide of 304 amino acids, with a calculated molecular weight of 34,285. The DCase gene was overexpressed under the control of the lac promoter, and DCase accounted for 50% of the soluble protein in the cells.
  The enzyme was purified and some properties were investigated. Both the optimum pH and the pH that gave greatest stability were about pH 7.0. The optimum temperature was 65°C, and the enzyme was stable at 55°C. The enzyme had strict specificity toward N-carbamyl-D-amino acids, and was inhibited by thiol reagents, Cu²⁺, Hg²⁺, Ag⁺, and ammonia.