AUTHOR=Crooks Casey , Bechle Nathan J. , St John Franz J. 

TITLE=A New Subfamily of Glycoside Hydrolase Family 30 with Strict Xylobiohydrolase Function

JOURNAL=Frontiers in Molecular Biosciences

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/molecular-biosciences/articles/10.3389/fmolb.2021.714238

DOI=10.3389/fmolb.2021.714238

ISSN=2296-889X

ABSTRACT=<p>The <italic>Acetivibrio</italic><italic>clariflavus</italic> (basonym: <italic>Clostridium clariflavum</italic>) glycoside hydrolase family 30 cellulosomal protein encoded by the Clocl_1795 gene was highly represented during growth on cellulosic substrates. In this report, the recombinantly expressed protein has been characterized and shown to be a non-reducing terminal (NRT)-specific xylobiohydrolase (<italic>Ac</italic>Xbh30A). Biochemical function, optimal biophysical parameters, and phylogeny were investigated. The findings indicate that <italic>Ac</italic>Xbh30A strictly cleaves xylobiose from the NRT up until an α-1,2-linked glucuronic acid (GA)-decorated xylose if the number of xyloses is even or otherwise a single xylose will remain resulting in a penultimate GA-substituted xylose. Unlike recently reported xylobiohydrolases, <italic>Ac</italic>Xbh30A has no other detectable hydrolysis products under our optimized reaction conditions. Sequence analysis indicates that <italic>Ac</italic>Xbh30A represents a new GH30 subfamily. This new xylobiohydrolase may be useful for commercial production of industrial quantities of xylobiose.</p>