title: Cloning, sequencing, and expression of the gene encoding extracellular alpha-amylase from Pyrococcus furiosus and biochemical characterization of the recombinant enzyme.
abstract: The gene encoding the hyperthermophilic extracellular alpha-amylase from Pyrococcus furiosus was cloned by activity screening in Escherichia coli. The gene encoded a single 460-residue polypeptide chain. The polypeptide contained a 26-residue signal peptide, indicating that this Pyrococcus alpha-amylase was an extracellular enzyme. Unlike the P. furiosus intracellular alpha-amylase, this extracellular enzyme showed 45 to 56% similarity and 20 to 35% identity to other amylolytic enzymes of the alpha-amylase family and contained the four consensus regions characteristic of that enzyme family. The recombinant protein was a homodimer with a molecular weight of 100,000, as estimated by gel filtration. Both the dimer and monomer retained starch-degrading activity after extensive denaturation and migration on sodium dodecyl sulfate-polyacrylamide gels. The P. furiosus alpha-amylase was a liquefying enzyme with a specific activity of 3,900 U mg-1 at 98 degrees C. It was optimally active at 100 degrees C and pH 5.5 to 6.0 and did not require Ca2+ for activity or thermostability. With a half-life of 13 h at 98 degrees C, the P. furiosus enzyme was significantly more thermostable than the commercially available Bacillus licheniformis alpha-amylase (Taka-therm).
authors.affiliation: Department of Biochemistry, Michigan State University, East Lansing 48824, USA.
authors.forename: G
authors.initials: G
authors.lastname: Dong
authors.forename: C
authors.initials: C
authors.lastname: Vieille
authors.forename: A
authors.initials: A
authors.lastname: Savchenko
authors.forename: J G
authors.initials: JG
authors.lastname: Zeikus
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000201:enzymology* / Q000235:genetics*; D001407:Bacillus / Q000201:enzymology / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D016384:Consensus Sequence; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016133:Polymerase Chain Reaction; D021382:Protein Sorting Signals / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D000516:alpha-Amylases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D017931:DNA Primers; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D000516:alpha-Amylases