A new bi-modular endo-β-1,4-xylanase KRICT PX-3 from whole genome sequence of Paenibacillus terrae HPL-003

A new bi-modular, wide pH spectrum and highly active xylanase KRICT PX3 (JF320814) isolated from Paenibacillus terrae HPL-003 (KCTC11987BP) has been cloned and expressed in Escherichia coli. Purified recombinant xylanase KRICT PX-3 (1,620 bp, 540aa, NCBI accession number ) showed highly active at 55 °C in pH 4.0–11.0, and stability for at least 24 h at 50 °C, and exhibited Km and Vmax of 0.2 mg/mL and 153.8 U/mg on birchwood xylan. Most common ions did not affect the enzyme activity at 1 mM concentration. This enzyme could belong to glycoside hydrolase family 10 because hydrolyzed glucuronoxylan and arabinoxylan substrate to xylobiose, xylotriose, and some traces of xylose as hydrolysis products. Model 3-D structure was composed of two domains, the catalytic domain of a (β/α)8 barrel fold while the small domain probably functions as a xylan binding domain, and the two domains are connected by a flexible linker peptide (PPLAIEKDIPSL). However, sequence alignment between xylan-binding module in this xylanase KRICT PX3 and CBM22 showed 21% of identity and 35% of similarity. This xylanase structure showed a distinctive group of enzyme cluster separately from the rest of GH10 xylanases, and seems to constitute a new type of xylanases.