title: Purification and characterisation of a salt-stable protease from the halophilic archaeon Halogranum rubrum.
abstract: BACKGROUND
  Because proteases play an important role in the fermentation of fish sauce, the purification and characterisation of an extracellular protease from the halophilic archaeon Halogranum rubrum was investigated.
  
  
  RESULTS
  The molecular mass of the protease was estimated to be approximately 47 kDa based on sodium dodecyl sulfate-polyacrylamide gel electropheresis (SDS-PAGE) and native-PAGE analysis. The optimum conditions for catalytic activity were pH 8.0 and 50°C. The protease showed alkaline stability (pH 7.0-10.0). The protease also exhibited novel catalytic ability over a broad range of salinity (NaCl 0-3 mol L-1). Calcium ion enhanced the proteolytic activity of the enzyme. The Kmand Vmaxvalues of the purified protease for casein were calculated to be 4.89 mg mL-1and 1111.11 U mL-1, respectively. The protease was strongly inhibited by ethylenediamine tetraacetic acid (EDTA) and phenylmethanesulfonyl fluoride (PMSF). Meanwhile, the protease was stable in the presence of Triton X-100, isopropanol, ethanol or dithio-bis-nitrobenzoic (DTNB), but was inhibited by sodium dodecyl sulfate (SDS), dimethyl sulfoxide (DMSO) or methanol. MALDI -TOF/TOF MS analysis revealed that the protease shared some functional traits with protease produced by Halogranum salarium. Furthermore, it exhibited high hydrolytic activity on silver carp myosin protein.
  
  
  CONCLUSIONS
  The protease is an alkaline and salt-tolerant enzyme that hydrolyses silver carp myosin with high efficiency. These excellent characteristics make this protease an attractive candidate for industrial use in low-salt fish sauce fermentation. © 2016 Society of Chemical Industry.
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Ruichang
authors.initials: R
authors.lastname: Gao
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Shi
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Liu
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Mengqin
authors.initials: M
authors.lastname: Zhao
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Henglin
authors.initials: H
authors.lastname: Cui
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yuan
mesh_terms: D000818:Animals; D002347:Carps; D004795:Enzyme Stability; D019605:Euryarchaeota / Q000201:enzymology*; D005396:Fish Products / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008970:Molecular Weight; D009218:Myosins / Q000737:chemistry; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000302:isolation & purification; D012965:Sodium Chloride / Q000737:chemistry
chemical_list: D012965:Sodium Chloride; D010447:Peptide Hydrolases; D009218:Myosins
keywords: Halogranum rubrum; characterisation; myosin hydrolysis; protease; purification; salt-adaption