Bacterial Enzyme Could Aid Prebiotic and Therapeutic Research

Carbohydrate chains, known as glycans, are complex sugar-based structures involved in various biological processes. Galactosides, a subgroup of glycans, are present in plants, animals and microorganisms. They contribute to plant cell wall composition and serve as prebiotic oligosaccharides that support gut health. Additionally, certain galactose-containing glycans are incorporated into processed foods for their potential benefits. Understanding the enzymes that break down these glycans is essential for advancing food science and health-related applications.

Identifying a novel β-galactosidase enzyme

β-Galactosidases are enzymes that release galactose from galactosides. While these enzymes exist in mammalian intestines and gut bacteria, their substrate specificity varies. Previous studies have shown that gut bacteria like Bifidobacterium help digest complex carbohydrates. However, the bacterium Bacteroides xylanisolvens is known for its broad carbohydrate utilization, though its enzymatic functions remain poorly understood.

A recent study led by researchers at Tokyo University of Science (TUS) has identified a novel β-galactosidase in B. xylanisolvens. This enzyme specifically targets galactose-containing glycans that may exhibit prebiotic properties. The research, published in Communications Biology on January 16, 2025, involved collaborators from Niigata University and Kagawa University.

“Although there are numerous types of glycans with diverse and complex structures, many glycans still have unknown functionality and potential uses. Since enzymes are essential for the synthesis of glycans, the search for new enzymes is extremely important. Our novel enzyme could be used to synthesize large amounts of unique glycans with prebiotic properties that may be beneficial to human health.”

Dr. Masahiro Nakajima.

Characterizing enzyme activity and specificity

The team analyzed multiple B. xylanisolvens genes encoding β-galactosidases and identified one, Bxy_22780, as encoding a previously unknown enzyme. Initial tests showed no activity against natural β-galactosides. However, when using α-D-galactosyl fluoride (α-GalF) as a donor substrate alongside galactose or D-fucose as acceptor substrates, reaction products were detected. Nuclear magnetic resonance analysis confirmed the formation of β-1,2-galactobiose, indicating the enzyme’s specificity.

Further investigation revealed that Bxy_22780 acts on galactooligosaccharides (GOS) with β-1,2-galactosidic linkages. Kinetic analysis demonstrated that the enzyme efficiently processes β-1,2-galactobiose and β-1,2-galactotriose. Structural studies using X-ray diffraction showed that the enzyme binds to methyl β-galactopyranose at a specific site, subsite +1. The structural analysis clarified why the enzyme selectively acts on β-1,2-galactooligosaccharides.

Potential implications for prebiotic research and therapeutics

While β-1,2-galactooligosaccharides are not yet proven to have prebiotic effects, their structural properties suggest possible health benefits. The discovery of this enzyme advances knowledge of glycan digestion and could inform the development of prebiotic products. Additionally, the enzyme’s specificity may have therapeutic implications. The parasite Trypanosoma cruzi, responsible for Chagas disease, produces glycans containing β-1,2-galactosidic linkages. The newly discovered enzyme could contribute to research on glycan-targeted treatments for such diseases.

The identification of Bxy_22780 represents a step forward in understanding bacterial carbohydrate metabolism. This enzyme may facilitate the production of novel prebiotic compounds and inform future applications in gut health and medical research.

Reference: Nakazawa Y, Kageyama M, Matsuzawa T, et al. Structure and function of a β-1,2-galactosidase from Bacteroides xylanisolvens, an intestinal bacterium. Commun Biol. 2025;8(1):66. doi: 10.1038/s42003-025-07494-1

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