Synthetic heterodisaccharides composed of glucose and xylose were tested as inducers of cellulose- and xylan-degrading enzymes in , and the inducing abilities were compared with those of sophorose and xylobiose or their positional isomers. Measurement of secreted and cell-associated enzyme activities revealed that the heterodisaccharides induced the synthesis of the cellulolytic and xylanolytic enzymes, 2--β-d-glucopyranosyl d-xylose (Glcβ1-2Xyl) being the most powerful inducer. Sophorose and 2--β-d-xylopyranosyl d-xylose (Xy1/β1-2Xy1), or their positional isomers, selectively induced the synthesis of cellulases and β-xylanases, respectively. An analysis of the extracellular enzymes (which were separated by isoelectric focusing followed by detection using chromogenic and fluorogenic substrates) showed that Glcβ1-2Xyl initiated the synthesis of specific endo-1,4-β-glucanases and specific endo-1,4-β-xylanases identical to those produced separately in response to sophorose or Xy1β1-2Xy1. Glcβ1-2Xy1 also induced specific endo-1,4-β-glucanases that hydrolysed 4-methylumbelliferyl β-lactoside at the agluconic bond. The results strengthen the concept of separate regulatory control of the synthesis of cellulases and β-xylanases. The results also suggest that mixed disaccharides, composed of glucose and xylose moieties, which may occur in nature, could play an important role in regulating the synthesis of wood-degrading enzymes.


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