title: Purification and characterization of thermostable endo-1,5-alpha-L-arabinase from a strain of Bacillus thermodenitrificans.
abstract: A strain of a thermophilic bacterium, tentatively designated Bacillus thermodenitrificans TS-3, with arabinan-degrading activity was isolated. It produced an endo-arabinase (ABN) (EC 3.2.1.99) and two arabinofuranosidases (EC 3.2.1.55) extracellularly when grown at 60 degrees C on a medium containing sugar beet arabinan. The ABN (tentatively called an ABN-TS) was purified 7,417-fold by anion-exchange, hydrophobic, size exclusion, and hydroxyapatite chromatographies. The molecular mass of ABN-TS was 35 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the isoelectric point was pH 4.5. The enzyme was observed to be more thermostable than known ABNs; it had a half-life of 4 h at 75 degrees C. The enzyme had optimal activity at 70 degrees C and pH 6.0. The enzyme had apparent K(m) values of 8.5 and 45 mg/ml and apparent V(max) values of 1.6 and 1.1 mmol/min/mg of protein against debranched arabinan (alpha-1,5-arabinan) and arabinan, respectively. The enzyme had no pectin-releasing activity (protopectinase activity) from sugar beet protopectin, differing from an ABN (protopectinase-C) from mesophilic Bacillus subtilis IFO 3134. The pattern of degradation of debranched arabinan by ABN-TS indicated that the enzyme was an endo-acting enzyme and the main end products were arabinobiose and arabinose. The results of preliminary experiments indicated that the culture filtrate of strain TS-3 is suitable for L-arabinose production from sugar beet pulp at high temperature.
authors.affiliation: Department of Food and Nutrition, Faculty of Agriculture, Kinki University, 3327-204 Naka-machi, Nara 631-8505, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takao
authors.forename: Kana
authors.initials: K
authors.lastname: Akiyama
authors.forename: Takuo
authors.initials: T
authors.lastname: Sakai
mesh_terms: D001407:Bacillus / Q000201:enzymology* / Q000254:growth & development; D004795:Enzyme Stability; D020459:Genes, rRNA; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D011134:Polysaccharides; D012336:RNA, Ribosomal, 16S; C030080:araban; D006026:Glycoside Hydrolases; C082526:arabinan endo-1,5-alpha-L-arabinosidase