Structural features of β-(1→4)-d-galactomannans of plant origin as a probe for β-(1→4)-mannanase polymeric substrate specificity

Statistical modeling was applied for describing structural features of β-(1→4)-d-galactomannans. According to the model suggested theoretical ratios of limiting degrees of locust bean, tara gum and guar gum galactomannan conversions by two β-(1→4)-mannanases of different origin (Myceliophthora thermophila and Trichoderma reesei) were calculated. Then the enzymes were tested for enzymatic hydrolysis of three considered galactomannans. Experimentally observed results were compared with theoretically calculated ones. It was shown that T. reesei β-mannanase attacks sequences of four and more unsubstituted mannopyranosyl residues in a row, while M. thermophila β-mannanase is a more specific enzyme and attacks sequences of five and more mannopyranosyl residues in a row. Considered statistical model and approach allows to characterize both galactomannan structures and enzyme requirements for regions of unsubstituted mannose residues for substrate hydrolysis.

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► Statistical model describes the distribution of substituted and unsubstituted galactomannan residues.
► This model interprets substrate specificity and limiting degree of substrate conversion data for two mannanases considered.
► According to this model, it was shown that two mannanases attack different sites in the galactomannan polymeric chain.