A novel bacterial GH30 xylobiohydrolase from Hungateiclostridium clariflavum
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BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS
A novel bacterial GH30 xylobiohydrolase from Hungateiclostridium clariflavum Katarína Šuchová 1
&
Vladimír Puchart 1 & Peter Biely 1
Received: 15 August 2020 / Revised: 23 October 2020 / Accepted: 12 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Typical bacterial GH30 xylanases are glucuronoxylanases requiring 4-O-methylglucuronic acid (MeGlcA) substitution of a xylan main chain for their action. They do not exhibit a significant activity on neutral xylooligosaccharides, arabinoxylan (AraX), or rhodymenan (Rho). In this work, the biochemical characterization of the bacterial Clocl_1795 xylanase from Hungateiclostridium (Clostridium) clariflavum DSM 19732 (HcXyn30A) is presented. Amino acid sequence analysis of HcXyn30A revealed that the enzyme does not contain amino acids known to be responsible for MeGlcA coordination in the 2b subsite of glucuronoxylanases. This suggested that the catalytic properties of HcXyn30A may differ from those of glucuronoxylanases. HcXyn30A shows similar specific activity on glucuronoxylan (GX) and Rho, while the specific activity on AraX is about 1000 times lower. HcXyn30A releases Xyl2 as the main product from the non-reducing end of different polymeric and oligomeric substrates. Catalytic properties of HcXyn30A resemble the properties of the fungal GH30 xylobiohydrolase from Acremonium alcalophilum, AaXyn30A. HcXyn30A is the first representative of a prokaryotic xylobiohydrolase. Its unique specificity broadens the catalytic diversity of bacterial GH30 xylanases. Key points • Bacterial GH30 xylobiohydrolase from H. clariflavum (HcXyn30A) has been characterized. • HcXyn30A releases xylobiose from the non-reducing end of different substrates. • HcXyn30A is the first representative of bacterial xylobiohydrolase. Keywords Xylanase . Xylobiohydrolase . Xylobiose . Hungateiclostridium clariflavum . Glycoside hydrolase family 30
Introduction Conversion of plant biomass into soluble sugars that can be fermented to various useful chemicals is of a high interest. The release of monomeric saccharides from complex polysaccharides bound in the plant matrix is, however, a difficult task. Concerted action of several different enzymes is needed. Some of the anaerobic bacteria produce a highly efficient multienzyme machinery called cellulosome. Hungateiclostridium (formerly Clostridium) clariflavum is one of a few thermophilic cellulosome-producing bacterial species. It was isolated from
* Katarína Šuchová [email protected] 1
Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38 Bratislava, Slovakia
an anaerobic sludge of a methanogenic bioreactor (Shiratori et al. 2009) and was shown to grow on cellulose and cellobiose. In 2012 the genome sequence of DSM 19732 strain was published and found to encode 72 putative glycoside hydrolases (GHs) belonging to 27 GH families (Izquierdo et al. 2012). Another H. clariflavum strain isolated from a compost is the strain 4-2a(Sizova et al
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