The active enzymes are important members of the cellular defense system protecting the cell from oxidative damage [1, 2]. high homology with those of known catalases from other bacteria. The catalase showed high alkali stability and thermostability. 1. Introduction Catalases (hydrogen peroxide: Dutasteride (Avodart) hydrogen peroxide oxidoreductase, EC 188.8.131.52) involve disproportionation of hydrogen peroxide to water and oxygen effectively, widely distributed in nature and found in bacterial, plant, and animal cells. The active enzymes are important members of the cellular defense system protecting the cell from oxidative damage [1, 2]. Cellular metabolism of molecular oxygen results in reactive oxygen species (ROS), such as superoxide anion radical (O2 ??), hydroxyl radical (OH?), and hydrogen peroxide (H2O2)  in all aerobically produced microorganisms. ROS are highly harmful to cells for they are implicated in damage to many biological macromolecules including proteins, DNA, and membrane lipids . Specific enzyme systems are used to eliminate ROS. Toxic O2 ?? is usually dismutated to H2O2 by superoxide dismutase, and accumulation of toxic H2O2 is usually prevented by catalase [2, 4]. Catalases include three families: monofunctional catalases, bifunctional catalases-peroxidases, and Mn catalases. Monofunctional catalases and bifunctional catalases are heme catalases, made up of iron-protoporphyrin IX as prosthetic group in their active sites, whereas Mn catalases are nonheme catalases. Catalases catalyze decomposed H2O2 to water and oxygen, whereas peroxidases are characterized by the oxidation of various organic compounds. Monofunctional catalases, made up of four subunits, are composed Dutasteride (Avodart) of two Trp53 classes based on the Dutasteride (Avodart) size of the subunits: small-subunit catalases ( 60?kDa) and large-subunit catalases ( 75?kDa) . In recent years, the use of H2O2 has grown rapidly for sterilization or bleaching processes in some medical, food, and textile operations. The removal of superabundant H2O2 that persists in products or surroundings by catalases is usually drawing attention as a substitute for chlorate compounds, which are toxicant and polluting. For this purpose, it is very necessary to produce an economical, highly active, and highly stable catalase. The applied research of catalases promotes the research of purification and biochemical properties of themselves [6C8]. In the previous research, we had screened out a marine strain with high catalase activity. The strain was recognized and designated asAcinetobacter Acinetobactersp. YS0810 (YS0810CAT). Here, we have explained the characterization of YS0810CAT, including molecular excess weight, absorption spectra, N-terminal sequence, alkali stability, and thermostability. The results of this study for YS0810CAT lay the foundation for its theoretical research and application in the medical and industrial fields. 2. Materials and Methods 2.1. Bacterial Strains and Cultivation The strainAcinetobactersp. YS0810 was isolated from Qingdao coastal, in China. The strain YS0810 was routinely cultivated aerobically in medium [2% (w/v) peptone, 0.2% (w/v) meat extract, 0.2% (w/v) NH4Cl, 0.2% (w/v) KH2PO4, 0.15% (w/v) KH2PO4] at 220?rpm on a rotary shaker at 28C for 24?h. 2.2. Materials Acrylamide, methylene-bis-acrylamide, N,N,N,N-tetramethylethylenediamine, and ammonium persulfate for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were purchased from Bio-Rad. Blue dextran, thyroglobulin, bovine catalase, bovine serum albumin, and lysozyme were purchased from Sigma. HiPrep DEAE FF 16/10 column, Superdex 200 10/300 GL column, and Resource Q column were purchased from General Electrics. All other chemicals were of the best purity available. 2.3. Protein Determination and Enzyme Assays for Catalase Activity Protein concentrations were decided using Bradford method , with bovine serum albumin as the standard. Protein purity was assayed by SDSCPAGE . Enzyme assays for catalase activity were measured on SHIMADZU UV-2550 spectrophotometer equipped with a Peltier-type cell heat controller. Assays were performed at 25C in 50?mM.