title: Thermodynamics and kinetic properties of halostable endoglucanase from Aspergillus fumigatus ABK9.
abstract: An endoglucanase from Aspergillus fumigatus ABK9 was purified from the culture extract of solid-state fermentation and its some characteristics were evaluated. The molecular weight of the purified enzyme (56.3 kDa) was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, zymogram analysis and confirmed by MALDI-TOF mass spectrometry. The enzyme was active optimally at 50 °C, pH 5.0 and stable over a broad range of pH (4.0-7.0) and NaCl concentration of 0-3.0 M. The pKa1 and pKa2 of the ionizable groups of the active sites were 2.94 and 6.53, respectively. The apparent Km , Vmax , and Kcat values for carboxymethyl cellulose were 6.7 mg ml(-1), 775.4 µmol min(-1) , and 42.84 × 10(4)  s(-1), respectively. Thermostability of the enzyme was evidenced by the high activation energy (91.45 kJ mol(-1)), large enthalpy for activation of denaturation (88.77 kJ mol(-1)), longer half-life (T1/2) (433 min at 50 °C), higher melting temperature (Tm ) (73.5 °C), and Q10 (1.3) values. All the characteristics favors its suitability as halotolerant and thermostable enzyme during bioprocessing of lignocellulosic materials.
authors.affiliation: Department of Microbiology, Vidyasagar University, Midnapore, West Bengal, India.
authors.forename: Arpan
authors.initials: A
authors.lastname: Das
authors.forename: Arijit
authors.initials: A
authors.lastname: Jana
authors.forename: Tanmay
authors.initials: T
authors.lastname: Paul
authors.forename: Suman Kumar
authors.initials: SK
authors.lastname: Halder
authors.forename: Kuntal
authors.initials: K
authors.lastname: Ghosh
authors.forename: Chiranjit
authors.initials: C
authors.lastname: Maity
authors.forename: Pradeep Kumar Das
authors.initials: PK
authors.lastname: Mohapatra
authors.forename: Bikas Ranjan
authors.initials: BR
authors.lastname: Pati
authors.forename: Keshab Chandra
authors.initials: KC
authors.lastname: Mondal
mesh_terms: D001232:Aspergillus fumigatus / Q000201:enzymology*; D002266:Carboxymethylcellulose Sodium / Q000378:metabolism; D002480:Cellulase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D012965:Sodium Chloride / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature
chemical_list: D012965:Sodium Chloride; D002480:Cellulase; D002266:Carboxymethylcellulose Sodium
keywords: Activation energy; Aspergillus fumigatus; Endoglucanase; Enthalpy; Thermostablility