Purification and Properties of an Extracellular Endo-1,4-β-Glucanase from Suspension-Cultured Poplar Cells

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An endo-1,4-β-glucanase (EC 3.2.1.4) was purified to apparent homogeneity from the culture medium of poplar (Populus alba L.) cells by sequential anion-exchange, hydrophobic, and gel-filtration chromatography. The preparation of extracellular β-glucanase was homogeneous on SDS-polyacrylamide gel electrophoresis (PAGE) and native PAGE. The molecular weight, as determined by SDS-PAGE was 50,000, whereas that determined by gel filtration was 40,000. The isoelectric point (pI) was 5.5. The purified enzyme catalyzed the endohydrolysis of carboxymethylcellulose with a pH optimum of 6.0 and a K_m of 1.0 mg ml^<-1>. The enzyme specifically cleaved the 1,4-β-glucosyl linkages of carboxymethylcellulose, swollen cellulose, lichenan and xyloglucan, although the last was hydrolyzed more slowly than the other tested substrates. The activity of the endo-1,4-β-glucanase increased up to the early stage of the mid-logarithmic phase of growth and then decreased rapidly, suggesting that the β-glucanase is induced before cell development.
日本植物生理学会の論文