Characterization of a Paenibacillus cell-associated xylanase with high activity on aryl-xylosides: a new subclass of family 10 xylanases.
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.
Gallardo
O
O
Department of Microbiology, Faculty of Biology, University of Barcelona, Avinguda Diagonal 645, 08028, Barcelona, Spain.
Diaz
P
P
Pastor
F I J
FI
D000595:Amino Acid Sequence; D001406:Bacillaceae / Q000166:cytology* / Q000201:enzymology*; D001412:Bacillus subtilis / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D005110:Extracellular Space; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase