Galactose-6-phosphate isomerase (LacAB)

Galactose-6-phosphate isomerase (EC 5.3.1.26) is a microbial enzyme that catalyzes the reversible isomerization of D-galactose-6-phosphate into D-tagatose-6-phosphate [3, 6]. This reaction is a critical step in the tagatose 6-phosphate pathway, which serves as a major route for the metabolism of lactose and galactose in several Gram-positive bacterial species, including human pathogens such as Staphylococcus aureus and Streptococcus pneumoniae [1, 2, 7]. The enzyme typically functions as a heteromultimeric complex consisting of two distinct subunits, LacA and LacB, which are encoded by the lacA and lacB genes respectively [1, 4]. In these bacteria, the pathway is essential for survival and growth on galactose-containing substrates when the more common Leloir pathway is absent or restricted [5]. From a pharmacological perspective, galactose-6-phosphate isomerase is investigated as a potential target for the development of novel antibacterial therapies [5, 8]. Because humans rely on the Leloir pathway for galactose metabolism and lack the tagatose 6-phosphate pathway entirely, selective inhibitors of this enzyme could theoretically disrupt bacterial energy production with minimal direct toxicity to human cells [6, 11]. Additionally, the enzyme is utilized in biotechnology for the biocatalytic production of rare sugars, such as D-tagatose and D-allose, which are used as low-calorie functional sweeteners and pharmaceutical precursors [5, 8].

Other names

Galactose-6-phosphate isomerase subunit LacAGalactose-6-phosphate isomerase subunit LacBD-galactose-6-phosphate aldose-ketose-isomeraseTagatose 6-phosphate pathway isomeraseLacAB complex

Inhibition of bacterial galactose metabolism and the tagatose 6-phosphate pathway to disrupt energy production in pathogenic bacteria.