Catalytic Properties and Partial Amino Acid Sequence of an Actinomycete Endo-(1→4)-β-D-Xylanase from Chainia Species

An endo-(l→4)-β- D -xylanase from a cellulase-free Chainia strain was substantially purified and subjected to amino acid sequencing. The first forty N-terminal amino acid residues show high homology with endo-xylanases from Bacillus pumilus, B . subtilis, B . circulans, and Schizophylum commune, less homology with endo-xylanases from Aureobasidium sp. and Pseudomonas fluorescens, and slight homology, but including a possible catalytic Asp residue, with catalytic domains of endo-xylanases from Clostridium thermocellum, Cryptococcus albidus, and an alkalophilic Bacillus and with a cellobiohydrolase from Cellulomonas fimi . The enzyme attacks substrates as small as xylotetraose and has xylosyltransferase activity. It is most active at pH 6 and 60°C and most stable between pHs 5 and 7.