title: Thermodynamic properties of the β-glucosidase from Thermotoga maritima extend the upper limit of thermophilicity.
abstract: Enzymes from thermophilic organisms are believed to be strong candidates for industrial applications due to their ability to withstand temperature-induced enzyme inactivation. The present study demonstrated molecular cloning, over-expression, purification and characterization of β-glucosidase from Thermotoga maritima. The bglA gene with a capacity to encode a 51 kDa enzyme was heterologously expressed in E. coli M15. The enzyme was produced @130 mgL(-1) in LB media and @440 mgL(-1) in Dubos salt medium accounting 40-47 % of total cellular soluble proteins when lactose was used as an inducer. The enzyme showed a peak activity between pH and temperature range of 5.0-7.0 and 80-100 °C, respectively. The activity was fairly stable up to 140 °C. The turnover rate (kcat) of the enzyme was 187.1±20 s(-1), whereas the Km and Vmax values were 0.56 mM and 238±2.4 IU mg(-1) protein, respectively. The enzyme was shown to have half-life of 136, 71 and 12.6 h at 80, 90 and 100 °C, respectively. Thermodynamics parameters including melting temperature (130 °C), activation energy for inactivation (36.92 kJmole(-1)), enthalpy (33.73 kJmole(-1)), Gibb's free energy (127.96 kJmole(-1)) and entropy (-246.46 Jmole(-1)K(-1)) have shown that the enzyme have enhanced hydrophobic interactions to prevent its thermal unfolding. These features endorse the industrial applications of the enzyme.
authors.forename: Muhammad A
authors.initials: MA
authors.lastname: Mehmood
authors.forename: Izzah
authors.initials: I
authors.lastname: Shahid
authors.forename: Khadim
authors.initials: K
authors.lastname: Hussain
authors.forename: Farooq
authors.initials: F
authors.lastname: Latif
authors.affiliation: National Institute for Biotechnology & Genetic Engineering, Faisalabad-38000, Pakistan. mibrahimrajoka47@gmail.com.
authors.forename: Muhammad I
authors.initials: MI
authors.lastname: Rajoka
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D020124:Thermotoga maritima / Q000201:enzymology* / Q000235:genetics; D001617:beta-Glucosidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D001617:beta-Glucosidase