Purification, Characterization, and Gene Sequencing of a Catalase from an Alkali- and Halo-tolerant Bacterium, Halomonas sp. SK1

Abstract

An alkali- and halo-tolerant bacterium with high catalase activity was isolated and identified as a new species of the genus Halomonas. Its catalase (HktA) was simply purified by two steps of liquid chromatography. A 71.4% yield of the catalase was obtained with 97% purity on SDS-PAGE. The specific activity of HktA (57,900 U/mg protein) was two times higher than that of bovine liver catalase. The purified enzyme is inhibited by KCN, NH₂OH, NaN₃, and 3-amino-1,2,4-triazole, active at pH 5.0-11.0, thermo-sensitive, and KCl- tolerant. HktA is suggested to be a typical catalase, a homotetrameric protein containing heme groups in the active sites. The nucleotide sequence of the catalase gene (hktA) comprises 1,530 bp, encoding a protein of 509 amino acid residues. The deduced amino acid sequence of the hktA shares 99% identity with that of Vibrio rumoiensis S-1^T.

• alkali-tolerant
• catalase
• Halomonas
• halotolerant