A thermophilic and thermostable beta-galactosidase activity was purified to homogeneity from crude extracts of the archaebacterium Sulpholobus solfataricus, by a procedure including ion-exchange and affinity chromatography. The homogeneous enzyme had a specific activity of 116.4 units/mg at 75 °C with o-nitrophenyl P-galactopyranoside as substrate. Molecular mass studies demonstrated that the S. solfataricus beta-galactosidase was a tetramer of 240 Ifr S 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 crossreact 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.
Thermostable beta-galactosidase from the archaebacterium Sulfolobus solfataricus. Purification and properties.
FM Pisani;R Rella;C Raia;C Rozzo;R Nucci;A Gambacorta;M Rossi
1990
Abstract
A thermophilic and thermostable beta-galactosidase activity was purified to homogeneity from crude extracts of the archaebacterium Sulpholobus solfataricus, by a procedure including ion-exchange and affinity chromatography. The homogeneous enzyme had a specific activity of 116.4 units/mg at 75 °C with o-nitrophenyl P-galactopyranoside as substrate. Molecular mass studies demonstrated that the S. solfataricus beta-galactosidase was a tetramer of 240 Ifr S 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 crossreact 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.