Bacterial enzyme releases sugars bound to protein fragments in breast milk
The sugars examined in the research belong to a group known as N-glycans. They can remain chemically attached to glycopeptides, small protein fragments, and must be detached before bacteria can use them as nutrients. Experiments found that PNGaseA preferentially acts on proteins that have already been broken into fragments. This preference helps explain how the bacteria obtain nutrients from milk components whose sugars are initially bound to other molecules.
The researchers used X-ray crystallography to examine the enzyme’s three-dimensional organisation. They identified a C-shaped cavity that recognises both the sugar and part of the protein fragment carrying it. The structure can adjust partially to its substrate, helping to separate the attached components. According to the researchers, this was the first observation of a structure of this type with a glycopeptide bound to it. The work is credited to Cassie R. Bakshani and colleagues in Nature Communications in 2026.
The findings concern the establishment of the intestinal microbial community during the first months of life. Feeding, the surrounding environment and exposure to different bacteria influence this process. Bacteria can draw nutrients from several carbohydrates in human milk, supporting their presence in the infant gut. The enzyme’s activity provides an explanation for how certain bacteria are adapted to obtaining nutrients in the intestines of breastfed newborns.
Breast milk supplies substances that can encourage the growth of particular microorganisms. The University of Birmingham notes that some of these components have a complexity that conventional infant formulas do not reproduce to an equivalent degree. Crouch considers that a better understanding of the interactions between milk components and bacteria could support the design of prebiotic ingredients intended to promote intestinal bacteria regarded as beneficial.
Ramón Hurtado-Guerrero, of the University of Zaragoza, also highlighted the importance of determining the enzyme’s structure. He said this knowledge could assist investigations of other proteins involved in processing sugars. The research examines the biochemical steps through which bacteria gain access to these nutrients.
In separate work in April 2026, Birmingham scientists investigated cooperation between Bifidobacterium bacteria and particular strains of Escherichia coli in breastfed infants. That research examined interactions among intestinal microorganisms during early life, alongside the work on bacterial use of milk components.
