Characterization of a Paenibacillus cell-associated xylanase with high activity on aryl-xylosides: a new subclass of family 10 xylanases

• Published in: Applied microbiology and biotechnology 2003-05, Vol.61 (3), p.226-233
• Main Authors: Gallardo, O, Diaz, P, Pastor, F.I.J
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Automation; Bacillaceae - cytology; Bacillaceae - enzymology; Bacillus (Bacteria); Bacillus subtilis; Bacillus subtilis - genetics; Base Sequence; Biodegradation; Biological and medical sciences; Biotechnology; catalytic activity; Cellular biology; Cloning, Molecular; Cluster analysis; E coli; enzyme activity; Enzymes; Extracellular Space; Fundamental and applied biological sciences. Psychology; hydrolysis; Microbiological chemistry; Molecular Sequence Data; nucleotides; open reading frames; Paenibacillus; Peptides; Phylogeny; Physiological aspects; Plasmids; Sequence Alignment; sequence homology; Sequence Homology, Amino Acid; signal peptide; Studies; Substrate Specificity; xylan; Xylan Endo-1,3-beta-Xylosidase; Xylanases; xylooligosaccharides; Xylosidases - chemistry; Xylosidases - genetics; Xylosidases - isolation & purification; Xylosidases - metabolism
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-003-1239-1

The sequence of gene xynB encoding xylanase B from Paenibacillus sp. BP-23 was determined. It revealed an open reading frame of 999 nucleotides encoding a protein of 38,561 Da. The deduced amino acid sequence of xylanase B shows that the N-terminal region of the enzyme lacks the features of a signal peptide. When the xylan-degrading system of Paenibacillus sp. BP-23 was analysed in zymograms, it revealed that xylanase B was not secreted to the extracellular medium but instead remained cell-associated, even in late stationary-phase cultures. When xynB was expressed in a Bacillus subtilis secreting host, it also remained associated with the cells. Sequence homology analysis showed that xylanase B from Paenibacillus sp. BP-23 belongs to family 10 glycosyl hydrolases, exhibiting a distinctive high homology to six xylanases of this family. The homologous enzymes were also found to be devoid of a signal peptide and seem to constitute, together with xylanase B, a separate group of enzymes. They all have two conserved amino acid regions not found in the other family 10 xylanases, and cluster in a separate group after dendrogram analysis. We propose that these enzymes constitute a new subclass of family 10 xylanases, that are cell-associated, and that hydrolyse the xylooligosaccharides resulting from extracellular xylan hydrolysis. Xylanase B shows similar specific activity on aryl-xylosides and xylans. This can be correlated to some, not yet identified, trait of catalytic activity of the enzyme on plant xylan.