title: Physicochemical characteristics of a thermostable gellan lyase from Geobacillus stearothermophilus 98.
abstract: A purified thermostable gellan lyase, produced by a thermophilic bacterium, Geobacillus stearothermophilus 98, was characterized in relation to its physicochemical properties. The gellan lyase was established to have a molecular weight of 216 kDa, defined by capillary gel electrophoresis. Amino acid analysis revealed high quantities of Lys, His, Ala, Val, Ile, Glx, and Pro residues. The circular dichroism revealed 45% beta-structure and practically lack of a-spiral domains. Kinetic studies showed high affinity of the enzyme to gellan as a substrate (Km = 0.21 microM). The thermal denaturation investigated by cicular dichroism showed a highly cooperative transition with a midpoint (Tm) at about 75 degrees C. A single product was identified after enzyme action on gellan. Large exothermic aggregation near Tm was observed by differential scanning calorimetry. Two types of gellan lyase crystals were reproducibly isolated.
authors.affiliation: Department of Extremophilic Bacteria, Institute of Microbiology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 26, Sofia 1113, Bulgaria.
authors.forename: Anna
authors.initials: A
authors.lastname: Derekova
authors.forename: Miroslava
authors.initials: M
authors.lastname: Atanassova
authors.forename: Petya
authors.initials: P
authors.lastname: Christova
authors.forename: Bojidar
authors.initials: B
authors.lastname: Tchorbanov
authors.forename: Alexandra
authors.initials: A
authors.lastname: Shosheva
authors.forename: Rossitsa
authors.initials: R
authors.lastname: Mandeva
authors.forename: Patricia
authors.initials: P
authors.lastname: Rodríguez-Alonso
authors.forename: Jose I
authors.initials: JI
authors.lastname: Garabal
authors.forename: Margarita
authors.initials: M
authors.lastname: Kambourova
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001407:Bacillus / Q000201:enzymology*; D002855:Chromatography, Thin Layer; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D007700:Kinetics; D011133:Polysaccharide-Lyases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D011133:Polysaccharide-Lyases; C091406:gellan lyase