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Expression and Characterization of a Modular Β-Mannanase of Bifidobacterium Adolescentis Carrying Mannan-Binding and Cell Association Motifs

Publiceringsår: 2012
Språk: Engelska
Publikation/Tidskrift/Serie: Applied and environmental microbiology
Dokumenttyp: Artikel
Förlag: American Society for Microbiology


The gene encoding β-mannanase (EC BaMan26A from the bacterium Bifidobacterium adolescentis (living in the human gut) was cloned and the gene product characterized. The enzyme was found to be modular and to contain a putative signal peptide. It possesses a catalytic module of the glycoside hydrolase family 26, a predicted immunoglobulin-like module and two putative carbohydrate-binding modules (CBMs) of family 23. The enzyme is likely cell attached either by the sortase mechanism (LPXTG motif) or via a C-terminal transmembrane helix. The gene was expressed in Escherichia coli without the native signal peptide or the cell anchor. Two variants were made: one containing all four modules, designated BaMan26A-101K, and one truncated before the CBMs, designated BaMan26A-53K. BaMan26A-101K, which contains the CBMs, showed an affinity to carob galactomannan having a dissociation constant of 0.34 μM (8.8 mg/l), whereas BaMan26A-53K didn't bind, showing that at least one of the putative CBMs of family 23 is mannan binding. For BaMan26A-53K, k(cat) was determined to be 444 s(-1) and K(M) 21.3 g/l using carob galactomannan as the substrate at the optimal pH of 5.3. Both of the enzyme variants hydrolyzed konjac glucomannan, as well as carob and guar gum galactomannans to a mixture of oligosaccharides. The dominant product from ivory nut mannan was found to be mannotriose. Mannobiose and mannotetraose were produced to a lesser extent, as shown by high-performance anion-exchange chromatography. Mannobiose was not hydrolyzed and mannotriose was hydrolyzed at a significantly slower rate than the longer oligosaccharides.



  • Biology and Life Sciences


  • ISSN: 1098-5336

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