Beta-galactosidase LacA (Limosilactobacillus reuteri) (LacA)

LacA beta-galactosidase is a glycoside hydrolase belonging to the GH42 family, primarily found in the probiotic bacterium Limosilactobacillus reuteri (formerly Lactobacillus reuteri) (Zheng et al., 2020). Unlike the more common GH2 family beta-galactosidases (LacLM), LacA is specialized for the metabolism of galactooligosaccharides (GOS) and alpha-galactosides like raffinose and stachyose (Pham et al., 2019). This enzyme is essential for the ecological fitness of L. reuteri in the gut, enabling it to utilize complex carbohydrates that are not easily digested by the host (Gopal et al., 2001). In therapeutic applications, beta-galactosidases are widely used as enzyme replacement therapies to alleviate symptoms of lactose intolerance by hydrolyzing lactose into glucose and galactose (NIH, 2024). LacA is also a key focus in the development of synbiotics, where it serves as the target for specific prebiotic substrates designed to selectively promote the growth of beneficial L. reuteri strains (Pham et al., 2019). Furthermore, the enzyme's transgalactosylation activity is exploited in the food industry for the large-scale synthesis of prebiotic GOS from lactose (Splechtna et al., 2007). While not a target for traditional inhibitory drugs, its activity is modulated by substrates like lactose and inhibited by reaction products such as galactose and glucose (Nguyen et al., 2006). Its role in gut health and its potential for metabolic engineering make it a significant molecule in both probiotic research and functional food technology (Gomaa, 2016).

Other names

LacAGH42 beta-galactosidaseBeta-D-galactosidaseLactaseLactobacillus reuteri LacA

The enzyme catalyzes the hydrolysis of beta-glycosidic bonds through a double-displacement mechanism, typically involving two glutamic acid residues that act as a nucleophile and an acid/base catalyst, respectively (Juers et al., 2012).