Abstract
In this study, the first xylantic enzyme from the family Marinifilaceae, XynSPP2, was identified from Marinifilaceae bacterium strain SPP2. Amino acid sequence analysis revealed that XynSPP2 is a rare Fn3-fused xylanase, consisting of a signal peptide, a fibronectin type-III domain (Fn3), and a C-terminal catalytic domain belonging to glycoside hydrolase family 10 (GH10). The catalytic domain shared 17–46% identities to those of biochemically characterized GH10 xylanases. Structural analysis revealed that the conserved asparagine and glutamine at the glycone −2/−3 subsite of GH10 xylanases are substituted by a tryptophan and a serine, respectively, in XynSPP2. Full-length XynSPP2 and its Fn3-deleted variant (XynSPP2ΔFn3) were overexpressed in Escherichia coli and purified by Ni-affinity chromatography. The optimum temperature and pH for both recombinant enzymes were 50°C and 6, respectively. The enzymes were stable under alkaline condition and at temperature lower than 50°C. With beechwood xylan as the substrate, XynSPP2 showed 2.8 times the catalytic efficiency of XynSPP2ΔFn3, indicating that the Fn3 module promotes xylanase activity. XynSPP2 was active toward xylooligosaccharides (XOSs) longer than xylotriose. Such a substrate preference can be explained by the unique −2/−3 subsite composition in the enzyme which provides new insight into subsite interaction within the GH10 family. XynSPP2 hydrolyzed beechwood xylan into small XOSs (xylotriose and xylotetraose as major products). No monosaccharide was detected by thin-layer chromatography which may be ascribed to putative transxylosylation activity of XynSPP2. Preferring long XOS substrate and lack of monosaccharide production suggest its potential in probiotic XOS manufacture.
Highlights
Plant material mainly consists of cellulose, hemicellulose, and lignin (Tuck et al, 2012)
The present paper reports the bioinformatic and biochemical characterization of XynSPP2
Marinifilaceae bacterium strain SPP2 is a recently isolated polar microorganism classified into the family Marinifilaceae (Watanabe et al, 2018)
Summary
Plant material mainly consists of cellulose, hemicellulose, and lignin (Tuck et al, 2012). A β1,4-linked xylopyranose polymer, is the most common constituent of hemicellulosic polysaccharide in the biosphere (Linares-Pasten et al, 2018). Intensive research focused on developing different innovative technologies to exploit xylan (Van Dyk and Pletschke, 2012). Enzymatic decomposition is attractive because it is environmentally friendly. Xylan biodegradation is carried out by many. A Novel Endoxylanase With Fn3 Domain hydrolytic enzymes. The enzymes that randomly break down the internal glycosidic bond in the linear xylan main chain are termed endo-β-1,4-xylanases 3.2.1.8, normally referred to as xylanases) (Nguyen et al, 2018) The enzymes that randomly break down the internal glycosidic bond in the linear xylan main chain are termed endo-β-1,4-xylanases (EC. 3.2.1.8, normally referred to as xylanases) (Nguyen et al, 2018)
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