Brown rot fungi rapidly degrade hemicellulose, which is recognized as a key decomposition process during the early stages of wood decay. Brown rot fungi possess multiple genes encoding hemicellulose-degrading enzymes, suggesting that enzymatic hydrolysis plays an important role in this process. Hemicellulases produced by these fungi often contain an additional domain classified as carbohydrate-binding module family 1 (CBM1), which can adsorb to cellulose. However, it remains unclear how the presence of CBM1 in hemicellulases influences their degradation activity. In this study, we focused on the xylanase GtGH10C from Gloeophyllum trabeum, a model brown rot fungus that possesses a CBM1 domain. Recombinant enzymes, GtGH10C and its CBM1-deficient mutant (GtGH10dCBM1), were produced, and their decomposition properties were investigated. In addition to purified xylan substrates, enzymatic activity was also evaluated using biomass substrates. Since the hemicellulose component differs depending on tree species, wood flour from both softwood and hardwood were used. As a result, no clear negative effects of CBM1 deficiency were observed when using purified xylan substrates. In hardwood flour, the absence of CBM1 clearly reduced enzymatic activity. In contrast, in softwood flour, CBM1 deficiency led to reduced activity at low enzyme concentrations, but at higher concentrations, the GtGH10dCBM1 exhibited greater activity.

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