The Processing of High-Molecular-Weight Xylanase (XynE, 110kDa) from Aeromonas caviae ME-1 to 60-kDa Xylanase (XynE_60) in Escherichia coli and Purification and Characterization of XynE_60(ENZYMOLOGY, PROTEIN ENGINEERING, AND ENZYME TECHNOLOGY)

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A xylanase gene (xynE) encoding XynE (110kDa) was cloned from a λ phage genomic library of Aeromonas caviae ME-1 which is a multiple-xylanase-producing bacterium. Upon nucleotide sequence analysis, we found that xynE comprises 2823 bp and encodes a protein of 941 amino acid residues (104,153 Da), which was similar to endo-β-1, 4-xylanases which are categorized to glycosyl hydrolase family 10. An Escherichia coli transformant that harbored pXED30 carrying xynE produced 110-, 84-, 72-, and 66-kDa xylanases in the cell-free extract, and 72-and 66-kDa xylanases in the culture supernatant. We pruified the 66-kDa xylanase to electrophoretic homogeneity from a culture supernatant by a series of column chromatographies. The calculated molecular mass of the purified xylanase determined by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was 60,154.50 Da, and the xylanase was designated XynE_60. Analysis of the N-terminal 10 amino acid residues and the determined molecular mass of XynE_60 revealed that XynE_60 is a product processed at the Gly_26-Gly_27 and Thr_565-Ala_566 sites of XynE by proteolytic cleavage. XynE_60 showed optimal activity at 55℃ and pH8.0, and was stable below 45℃ and at pH7.0-8.5. The K_m and V_max of XynE_60 were calculated to be 8.1 mg/ml and 6897 nkat/mg, respectively.
社団法人日本生物工学会の論文
2003-01-25