INDUCTION OF CELLULOSE-DEGRADING AND XYLAN-DEGRADING ENZYME-SYSTEMS IN ASPERGILLUS-TERREUS BY HOMODISACCHARIDES AND HETERODISACCHARIDES COMPOSED OF GLUCOSE AND XYLOSE

Synthetic heterodisaccharides composed of glucose and xylose were tested as inducers of cellulose- and xylandegrading enzymes in Aspergillus terreus, 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-O-beta-D-glucopyranosyl D-xylose (Glc-beta-1-2Xyl) being the most powerful inducer. Sophorose and 2-O-beta-D-xylopyranosyl D-xylose (Xyl-beta-1-2Xyl), or their positional isomers, selectively induced the synthesis of cellulases and beta-xylanases, respectively. An analysis of the extracellular enzymes (which were separated by isoelectric focusing followed by detection using chromogenic and fluorogenic substrates) showed that Glc-beta-1-2Xyl initiated the synthesis of specific endo-1,4-beta-glucanases and specific endo-1,4-beta-xylanases identical to those produced separately in response to sophorose or endo-1,4-beta-glucanases that hydrolysed 4-methylumbelliferyl beta-lactoside at the agluconic bond. The results strengthen the concept of separate regulatory control of the synthesis of cellulases and beta-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.