title: Cloning, expression and biochemical characterisation of a unique thermostable pullulan-hydrolysing enzyme from the hyperthermophilic archaeon Thermococcus aggregans.
abstract: The gene for a new type of pullulan hydrolase from the hyperthermophilic archaeon Thermococcus aggregans was cloned and expressed in Escherichia coli. The 2181-bp open reading frame encodes a protein of 727 amino acids. A hypothetical membrane linker region was found to be cleaved during processing in E. coli. The recombinant enzyme was purified 70-fold by heat treatment, affinity and anion exchange chromatography. Optimal activity was detected at 95 degrees C at a broad pH range from 3.5 to 8.5 with an optimum at pH 6.5. More than 35% of enzymatic activity was detected even at 120 degrees C. The enzyme was stable at 90 degrees C for several hours and exhibited a half-life of 2.5 h at 100 degrees C. Unlike all pullulan-hydrolysing enzymes described to date, the enzyme is able to attack alpha-1,6- as well as alpha-1,4-glycosidic linkages in pullulan leading to the formation of a mixture of maltotriose, panose, maltose and glucose. The enzyme is also able to degrade starch, amylose and amylopectin forming maltotriose and maltose as main products.
authors.affiliation: Institute of Technical Microbiology, Technical University Hamburg-Harburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Niehaus
authors.forename: A
authors.initials: A
authors.lastname: Peters
authors.forename: T
authors.initials: T
authors.lastname: Groudieva
authors.forename: G
authors.initials: G
authors.lastname: Antranikian
mesh_terms: D000595:Amino Acid Sequence; D001482:Base Composition; D001483:Base Sequence; D003001:Cloning, Molecular; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013213:Starch / Q000378:metabolism; D013696:Temperature; D019712:Thermococcus / Q000201:enzymology* / Q000235:genetics
chemical_list: D019641:DNA, Archaeal; D011994:Recombinant Proteins; D013213:Starch; D006026:Glycoside Hydrolases; C100181:pullulanase