title: Characterization of a cold-adapted and salt-tolerant esterase from a psychrotrophic bacterium Psychrobacter pacificensis.
abstract: An esterase gene, est10, was identified from the genomic library of a deep-sea psychrotrophic bacterium Psychrobacter pacificensis. The esterase exhibited the optimal activity around 25 °C and pH 7.5, and maintained as high as 55.0 % of its maximum activity at 0 °C, indicating its cold adaptation. Est10 was fairly stable under room temperatures, retaining more than 80 % of its original activity after incubation at 40 °C for 2 h. The highest activity was observed against the short-chain substrate p-nitrophenyl butyrate (C4) among the tested p-nitrophenyl esters (C2-C16). It was slightly activated at a low concentration (1 mM) of Zn(2+), Mg(2+), Ba(2+), Ca(2+), Cu(2+), Fe(3+), urea and EDTA, but was inhibited by DTT and totally inactivated by PMSF. Interestingly, increased salinity considerably stimulated Est10 activity (up to 143.2 % of original activity at 2 M NaCl) and stability (up to 126.4 % after incubation with 5 M NaCl for 6.5 h), proving its salt tolerance. 0.05 and 0.1 % Tween 20, Tween 80, Triton X-100 and CHAPS increased the activity and stability of Est10 while SDS, CTAB had the opposite effect. Est10 was quite active after incubation with several 30 % organic solvents (methanol, DMSO, ethanediol) but exhibited little activity with 30 % isopropanol, ethanol, n-butanol and acetonitrile.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
authors.forename: Guojie
authors.initials: G
authors.lastname: Wu
authors.forename: Gaobing
authors.initials: G
authors.lastname: Wu
authors.forename: Tao
authors.initials: T
authors.lastname: Zhan
authors.forename: Zongze
authors.initials: Z
authors.lastname: Shao
authors.forename: Ziduo
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D002087:Butyrates / Q000737:chemistry; D020134:Catalytic Domain; D002413:Cations, Divalent / Q000737:chemistry; D004950:Esterases / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D055550:Protein Stability; D044096:Psychrobacter / Q000201:enzymology*; D055049:Salt Tolerance; D013379:Substrate Specificity; D013696:Temperature; D014508:Urea / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D002087:Butyrates; D002413:Cations, Divalent; C033592:4-nitrophenyl butyrate; D014508:Urea; D004950:Esterases