Characterization of recombinant β-fructofuranosidase from Bifidobacterium adolescentis G1

<p>Abstract</p> <p>Background</p> <p>We have previously reported on purification and characterization of β-fructofuranosidase (β-FFase) from <it>Bifidobacterium adolescentis </it>G1. This enzyme showed high activity of hydrolysis on fructo-oligosaccharides with a low degree of polymerization. Recently, genome sequences of <it>B. longum </it>NCC2705 and <it>B. adolescentis </it>ATCC 15703 were determined, and <it>cscA </it>gene in the both genome sequences encoding β-FFase was predicted. Here, cloning of <it>cscA </it>gene encoding putative β-FFase from <it>B. adolescentis </it>G1, its expression in <it>E. coli </it>and properties of the recombinant protein are described.</p> <p>Results</p> <p>Using the information of <it>cscA </it>gene from <it>Bifidobacterium adolescentis </it>ATCC 15703, <it>cscA </it>gene from <it>B. adolescentis </it>G1 was cloned and sequenced. The N-terminal amino acid sequence of purified β-FFase from <it>B. adolescentis </it>G1 was identical to the deduced amino acid sequences of <it>cscA </it>gene from <it>B. adolescentis </it>G1. To confirm the translated product of the <it>cscA </it>gene, the recombinant protein was expressed in <it>Escherichia coli</it>. Molecular mass of the purified recombinant enzyme was estimated to be about 66,000 by SDS-PAGE and 60,300 by MALDI TOF-MS. The optimum pH of the enzyme was 5.7 and the enzyme was stable at pH 5.0-8.6. The thermostability of the enzyme was up to 50°C. The <it>K</it>_m(mM), <it>V</it>_max(μmol/mg of protein/min), <it>k</it>₀(sec^-1) and <it>k</it>₀/<it>K</it>_m(mM^-1sec^-1) for 1-kestose, neokestose, nystose, fructosylnystose, sucrose and inulin were 1.7, 107, 107.5, 63.2, and 1.7, 142, 142.7, 83.9, and 3.9, 152, 152.8, 39.2, and 2.2, 75, 75.4, 34.3, and 38, 79, 79.4, 2.1, and 25.9, 77, 77.4, 3.0, respectively. The hydrolytic activity was strongly inhibited by AgNO₃, SDS, and HgCl₂.</p> <p>Conclusion</p> <p>The recombinant enzyme had similar specificity to the native enzyme, high affinity for 1-kestose, and low affinity for sucrose and inulin, although properties of the recombinant enzyme showed slight difference from those of the native one previously described.</p