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

Abstract

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 (1,620bp, 540aa, NCBI accession number JF320814) showed highly active at 55°C in pH 4.0–11.0, and stability for at least 24h at 50°C, and exhibited Km and Vmax of 0.2mg/mL and 153.8U/mg on birchwood xylan. Most common ions did not affect the enzyme activity at 1mM 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.