Endo-1,5-α-L-arabinanase from a Subseafloor Bacillus subtilis: Purification, Characterization and Nucleotide Sequence of Its Gene

抄録

Four arabinan-degrading enzymes are produced by Bacillus subtilis JAM A-3-6, which was isolated from a subseafloor sediment core from 0.5 m below seafloor at a water depth of 1,180 m off the Shimokita Peninsula in Japan. One of the enzymes (AbnAF25) was purified from a culture broth. The molecular mass of the enzyme was around 28 kDa as judged by SDS-polyacrylamide gel electrophoresis. The optimal pH and temperature were pH 6.3 and 60°C in phosphate buffer. AbnAF25 degraded well debranched arabinan, linear arabinan, and arabino-oligosaccharaides, but not arabinoxylan, arabinogalactan or p-nitrophenyl-α-L-arabinofuranoside, which classifies the enzyme as an endo-1,5-α-L-arabinanase. The end products from linear arabinan were mainly arabinose, arabinobiose and arabinotriose. The gene for AbnAF25 was cloned and sequenced. The deduced amino acid sequence of the enzyme revealed the highest similarity to the arabinanase of B. amyloliquefaciens with 83% identity. As AbnAF25 did not show the definite characterization of a subseafloor enzyme, strain JAM A-3-6 seems to be probably dropped or co-sedimented with a soil component.