β-galactanase: an effective tool for the degradation of plant β-ᴅ-galactan.

βGalactanases specifically hydrolyze the interglycosidic bonds of galactose residues in galactan and arabinogalactan, and they are widely distributed in both prokaryotes and eukaryotes. In this review, β-galactanases, including β-1,3-galactanase, β-1,4-galactanase, and β-1,6-galactanase, are summarized from both theoretical and applied perspectives. Studies have demonstrated that β-galactanases primarily belong to the glycoside hydrolase (GH) families 30, 43, and 53. The catalytic mechanisms of the GH30 and GH53 families follow a typical retention hydrolysis mechanism, while only members of the GH43 family adhere to the inverting hydrolysis mechanism. Due to structural differences among β-galactanases, their enzymatic properties and substrate specificities also exhibit significant variations. β-Galactanases have a wide range of applications. For example, β-1,4-galactanases are extensively used in the preparation of galacto-oligosaccharides (GOS) as a food additive and as a fingerprinting tool for medicinal plants. β-1,3-Galactanases and β-1,6-galactanases are less commonly used but are highly effective tools for the analysis of arabinogalactan-II (AG-II) pectin. Furthermore, to expand the application spectrum of β-galactanases, the preparation methods and basic enzymatic properties of these enzymes are summarized. The results demonstrate that β-galactanases have broad application prospects.