title: Purification and characterization of a highly thermostable esterase from the actinobacterium Geodermatophilus obscurus strain G20.
abstract: Intracellular thermostable esterase produced by the extremophilic Geodermatophilus obscurus G20 was purified to homogeneity by a heat treatment, followed by an anion-exchange chromatography, and then characterized. The molecular weight of the purified enzyme determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was shown to be approximatively 55 kDa. The enzyme showed an optimal activity between pH 8.0 and 9.0 and was stable in the pH range 7.0-10.0. Moreover, it is highly thermostable, with a residual activity greater than 90% after incubation at 80 °C for more than 10 h. The enzyme showed preference for esters of p -nitrophenol with short chain fatty acid. When the p -nitrophenyl acetate (C2) was used as substrate, the Michaelis-Menten constant (K(m) ) and maximum velocity for the reaction (V(max) ) of esterase were 400 μM and 2500 U/mg protein, respectively. The effect of phenylmethanesulphonyl fluoride (PMSF), a serine-specific inhibitor, on the enzyme activity suggested that the thermostable esterase belong to the serine hydrolase group. Because of its high thermostability, activity at alkaline pH, tolerance to methanol and various metal ions and specificity for short chain fatty acids, this enzyme showed high potential for use in biocatalysis. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
authors.affiliation: Laboratoire Microorganismes et Biomolécules Actives, Campus Universitaire, Tunis, Tunisia. atef.jaouani@issbat.rnu.tn
authors.forename: Atef
authors.initials: A
authors.lastname: Jaouani
authors.forename: Mohamed
authors.initials: M
authors.lastname: Neifar
authors.forename: Adnen
authors.initials: A
authors.lastname: Hamza
authors.forename: Semia
authors.initials: S
authors.lastname: Chaabouni
authors.forename: Maria Jesus
authors.initials: MJ
authors.lastname: Martinez
authors.forename: Maher
authors.initials: M
authors.lastname: Gtari
mesh_terms: D039903:Actinobacteria / Q000201:enzymology*; D055162:Biocatalysis; D004795:Enzyme Stability; D004950:Esterases / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008670:Metals / Q000737:chemistry; D008970:Molecular Weight; D012997:Solvents / Q000737:chemistry; D013696:Temperature
chemical_list: D007477:Ions; D008670:Metals; D012997:Solvents; D004950:Esterases