Functional Characterization of Endo- and Exo-Hydrolase Genes in Arabinan Degradation Gene Cluster of Bifidobacterium longum subsp. suis

• Published in: International journal of molecular sciences Vol. 25; no. 6; p. 3175
• Main Authors: Kang, Yewon, Choi, Chang-Yun, Kang, Jihun, Ju, Ye-Rin, Kim, Hye Bin, Han, Nam Soo, Kim, Tae-Jip
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09.03.2024; MDPI
• Subjects: Amino acids; arabinan degradation gene cluster; Arabinose; Bifidobacterium; Bifidobacterium longum subsp. suis; Bowel disease; Cluster analysis; endo-α-(1,5)- l -arabinanases (ABNs); Enzymes; exo-α- l -arabinofuranosidases (ABFs); Genes; Genomes; Glycoside Hydrolases - metabolism; hydrolytic modes of action; Metabolism; Microorganisms; Multigene Family; Oligosaccharides; Polymers; Polysaccharides - metabolism; Prebiotics; Probiotics; Substrate Specificity; hydrolytic modes of action; exo-α-l-arabinofuranosidases (ABFs); endo-α-(1,5)-l-arabinanases (ABNs); arabinan degradation gene cluster; Bifidobacterium longum subsp. suis
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms25063175

Bifidobacteria are probiotic microorganisms commonly found in the gastrointestinal tract, some of which are known to utilize linear arabino-oligosaccharides (AOS) as prebiotic carbohydrates. In general, the synergistic actions of exo-type α-l-arabinofuranosidases (ABFs) and endo-α-1,5-l-arabinanases (ABNs) are required for efficient arabinan degradation. In this study, the putative gene cluster for arabinan degradation was discovered in the genome of subsp. . It consists of a variety of genes encoding exo- and endo-hydrolases, sugar-binding proteins, ABC-binding cassettes, and transcriptional regulators. Among them, two endo-ABNs GH43 (BflsABN43A and BflsABN43B), two exo-ABFs GH43 (BflsABF43A and BflsABF43B), and an exo-ABF GH51 (BflsABF51) were predicted to be the key hydrolases for arabinan degradation. These hydrolase genes were functionally expressed in , and their enzymatic properties were characterized. Their synergism in arabinan degradation has been proposed from the detailed modes of action. Extracellular endo-BflsABN43A hydrolyzes sugar beet and debranched arabinans into the short-chain branched and linear AOS. Intracellularly, AOS can be further degraded into l-arabinose via the cooperative actions of endo-BflsABN43B, exo-BflsABF43A with debranching activity, α-1,5-linkage-specific exo-BflsABF43B, and exo-BflsABF51 with dual activities. The resulting l-arabinose is expected to be metabolized into energy through the pentose phosphate pathway by three enzymes expressed from the operon of bifidobacteria. It is anticipated that uncovering arabinan utilization gene clusters and their detailed functions in the genomes of diverse microorganisms will facilitate the development of customized synbiotics.