title: Thermostable beta-galactosidase from the archaebacterium Sulfolobus solfataricus. Purification and properties.
abstract: A thermophilic and thermostable beta-galactosidase activity was purified to homogeneity from crude extracts of the archaebacterium Sulfolobus solfataricus, by a procedure including ion-exchange and affinity chromatography. The homogeneous enzyme had a specific activity of 116.4 units/mg at 75 degrees C with o-nitrophenyl beta-galactopyranoside as substrate. Molecular mass studies demonstrated that the S. solfataricus beta-galactosidase was a tetramer of 240 +/- 8 kDa composed of similar or identical subunits. Comparison of the amino acid composition of beta-galactosidase from S. solfataricus with that from Escherichia coli revealed a lower cysteine content and a lower Arg/Lys ratio in the thermophilic enzyme. A rabbit serum, raised against the homogeneous enzyme did not cross-react with beta-galactosidase from E. coli. The enzyme, characterized for its reaction requirements and kinetic properties, showed a thermostability and thermophilicity notably greater than those reported for beta-galactosidases from other mesophilic and thermophilic sources.
authors.affiliation: Istituto di Biochimica delle Proteine ed Enzimologia, Consiglio Nazionale delle Ricerche, Napoli, Italia.
authors.forename: F M
authors.initials: FM
authors.lastname: Pisani
authors.forename: R
authors.initials: R
authors.lastname: Rella
authors.forename: C A
authors.initials: CA
authors.lastname: Raia
authors.forename: C
authors.initials: C
authors.lastname: Rozzo
authors.forename: R
authors.initials: R
authors.lastname: Nucci
authors.forename: A
authors.initials: A
authors.lastname: Gambacorta
authors.forename: M
authors.initials: M
authors.lastname: De Rosa
authors.forename: M
authors.initials: M
authors.lastname: Rossi
mesh_terms: D000596:Amino Acids / Q000302:isolation & purification; D001105:Archaea / Q000201:enzymology*; D001419:Bacteria / Q000201:enzymology*; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003432:Cross-Linking Reagents; D004586:Electrophoresis / Q000379:methods; D004795:Enzyme Stability; D005696:Galactosidases / Q000302:isolation & purification*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007120:Immunochemistry; D007525:Isoelectric Focusing; D007700:Kinetics; D001616:beta-Galactosidase / Q000302:isolation & purification*
chemical_list: D000596:Amino Acids; D003432:Cross-Linking Reagents; D005696:Galactosidases; D001616:beta-Galactosidase