Lactobacillus reuteri beta-galactosidase (LacA) (LacA)

Lactobacillus reuteri LacA is a specialized beta-galactosidase enzyme belonging to the Glycoside Hydrolase family 42 (GH42), primarily found in the probiotic bacterium Limosilactobacillus reuteri (formerly Lactobacillus reuteri). Unlike the more common GH2 family beta-galactosidases that specialize in lactose hydrolysis, LacA is specifically adapted to degrade complex galactooligosaccharides (GOS) and alpha-galactosides such as raffinose and stachyose [1, 6, 16]. This enzymatic activity is crucial for the ecological fitness and competitive colonization of L. reuteri within the human gastrointestinal tract, as it allows the bacterium to utilize specific dietary fibers as a primary energy source [1, 2, 10]. In clinical and biotechnological contexts, LacA is considered a key component of synbiotic therapies, where prebiotics like GOS are administered to selectively promote the growth and metabolic activity of the probiotic [3, 4, 10]. By facilitating the breakdown of these substrates, LacA supports the probiotic's ability to modulate the host immune system, strengthen the intestinal barrier, and produce beneficial metabolites like short-chain fatty acids [5, 7, 12]. Furthermore, its activity contributes to the alleviation of symptoms associated with lactose intolerance and infant colic by assisting in the digestion of galactose-containing sugars [11, 12].

Other names

GH42 beta-galactosidaseBeta-D-galactosidaseGalactoside hydrolaseLimosilactobacillus reuteri LacAGalactooligosaccharide hydrolase

Hydrolysis of terminal beta-galactosyl residues from galactooligosaccharides and other beta-galactosides to provide a carbon source for the probiotic bacterium, thereby enhancing its survival, colonization, and beneficial metabolic activity in the host gastrointestinal tract.