Characterization of NfGHX : a founding member of a new glycoside hydrolase family from the anaerobic fungus Neocallimastix frontalis

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Uddin, Muhammed Salah
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta : University of Lethbridge, Dept. of Biological Sciences
The discovery and characterization of enzymes that catalyze new reactions, and increase the rate or efficiency of bioconversion are promising lines of biotechnological research. In this regard the rumen anaerobic fungi represent an underexploited source of novel carbohydrate active enzymes that are active on recalcitrant plant cell wall polysaccharides. In this study, four rumen fungal genes (Nf2152, Nf2215, Nf2523 and Pr2455) were identified as functional CAZymes that represent founding members of a new GH family, referred to here as ‘GHX’. Two members of GHX, Nf2152 and Nf2523, were functionally characterized, and it was discovered that they have two different activities. Nf2152 releases a single product (β-1,2-arabinobiose) from sugar beet arabinan (SBA), and β-1,2-arabinobiose and a galactoarabinose with an unknown linkage from rye arabinoxylan (RAX). Nf2523 exclusively produces galactoarabinose from RAX. To the best of my knowledge, this represents the first reported galactoarabinobiosidase. Both β-1,2-arabinobiose and galactoarabinose are not conventional structures within SBA and RAX, and in fact are more likely released from the glycan side chains of arabinogalactan proteins (AGPs) that co-purify with the polysaccharides. In this regard, the GHXs studied here represent valuable tools for sequencing diverse AGP glycans and assisting in their bioconversion for industrial applications, such as animal production.
arabinose , enzyme discovery , galactose , glycoside hydrolase , rumen fungi