# The Bifidobacterium adolescentis BAD_1527 gene encodes GH43_22 α-L-arabinofuranosidase of AXH-m type

## TL;DR

A gene in Bifidobacterium adolescentis encodes an enzyme that specifically breaks down certain plant sugars, but not others.

## Contribution

The study clarifies the specific enzymatic activity of the BAD_1527 gene product as an α-L-arabinofuranosidase with AXH-m specificity.

## Key findings

- The BAD_1527 gene product releases xylose only from artificial substrates, not natural ones.
- The enzyme efficiently debranches arabinoxylan and branched arabinan but not doubly arabinosylated residues.
- L-Arabinose is the only sugar released from natural substrates by the enzyme.

## Abstract

Bifidobacterium adolescentis gene BAD_1527 has previously been suggested to code for a β-xylosidase (Kobayashi et al., Mar Drugs 18:174, 2020). Our detailed investigation of the substrate specificity of the GH43_22 protein using a wide spectrum of natural and artificial substrates showed that the enzyme hydrolyzed neither linear xylooligosaccharides nor glucuronoxylan. Xylose was released only from the artificial 4-nitrophenyl β-D-xylopyranoside (1.58 mU/mg). The corresponding α-L-arabinofuranoside was by three orders of magnitude better substrate (2.17 U/mg). Arabinose was the only monosaccharide liberated from arabinoxylan and α-1,3- or α-1,2-singly arabinosylated xylooligosaccharides. Moreover, the enzyme efficiently debranched sugar beet arabinan and singly arabinosylated α-1,5-L-arabinooligosaccharides, although short linear α-1,5-L-arabinooligosaccharides were also slowly degraded. On the other hand, debranched arabinan, arabinogalactan as well as 2,3-doubly arabinosylated main chain residues of arabinan and arabinoxylan did not serve as substrates. Thus, the enzyme encoded by the BAD_1527 gene is a typical α-L-arabinofuranosidase of AXH-m specificity.

The online version contains supplementary material available at 10.1186/s13568-024-01738-9.

BAD_1527 gene encodes a protein releasing xylose from NPX, but not natural substratesL-Arabinose is released from natural substrates, similarly to other GH43_22 membersThe enzyme debranches arabinoxylan, branched arabinan and derived oligosaccharides

BAD_1527 gene encodes a protein releasing xylose from NPX, but not natural substrates

L-Arabinose is released from natural substrates, similarly to other GH43_22 members

The enzyme debranches arabinoxylan, branched arabinan and derived oligosaccharides

The online version contains supplementary material available at 10.1186/s13568-024-01738-9.