The motivation is stark. Epidemiological projections cited in the study estimate that roughly 589 million adults were living with diabetes in 2024, a figure expected to climb to about 852.5 million by 2050. Gout cases, meanwhile, are projected to reach 95.8 million globally by mid-century. Current drugs such as acarbose, sitagliptin and allopurinol work well but carry drawbacks, from gastrointestinal discomfort to rare but serious hypersensitivity reactions. That has pushed researchers toward food-derived bioactive peptides, which offer high bioavailability and low toxicity as candidates for nutritional intervention.

Goat milk proteins, dominated by caseins and whey proteins, are attractive raw material because goat milk is more digestible and less allergenic than cow milk. Yet most goat milk products remain traditional powders with low added value. The team, led by Xinru Yu and Guowei Shu, set out to change that by asking a question few had tackled: could a single goat milk hydrolysate inhibit enzymes relevant to both glucose regulation and uric acid production at the same time?

The answer required finding the right enzymes for the job. The researchers screened nine food-grade proteases, hydrolyzing reconstituted goat milk for five hours and measuring the degree of peptide bond cleavage along with inhibitory activity against alpha-glucosidase, which breaks down dietary carbohydrates; dipeptidyl peptidase-IV, or DPP-IV, the incretin-degrading enzyme targeted by sitagliptin; and xanthine oxidase, the purine-metabolism enzyme blocked by allopurinol. Alkaline protease produced the deepest hydrolysis, but papain stood out for inhibitory power, achieving up to 53.37 percent alpha-glucosidase inhibition and 97.08 percent DPP-IV inhibition, while a neutral protease delivered the strongest xanthine oxidase blockade.

Because single enzymes rarely produce a peptide mix that hits all three targets, the team combined the four best performers. After testing stability under simulated gastrointestinal digestion and heat treatments mimicking pasteurization, the papain plus neutral protease pairing emerged as the winner. The optimal ratio, determined on an activity-unit basis, was one part papain to two parts neutral protease. Response surface methodology with a Box-Behnken design then fine-tuned the process, revealing that lower enzyme dosage, moderate temperature and extended time favored activity. The final recipe: 3000 units of enzyme per gram of protein at 50 degrees Celsius for roughly 4.1 hours.

Validation experiments confirmed the model’s predictions. Under optimized conditions, the hydrolysate inhibited alpha-glucosidase by 73.05 percent, DPP-IV by 88.63 percent and xanthine oxidase by 80.69 percent, matching the predicted values within statistical error. Benchmarking against standard curves showed the hydrolysate performed comparably to 68 micrograms per milliliter of acarbose, 2.87 micrograms per milliliter of sitagliptin and 64.73 micrograms per milliliter of allopurinol in the respective in vitro assays, though the authors caution that such comparisons serve only as internal references for complex peptide mixtures.

To find the molecules behind the activity, the team filtered the hydrolysate below 10 kilodaltons, separated it by preparative chromatography and analyzed the most potent fraction by liquid chromatography-tandem mass spectrometry. Twenty-four peptides emerged, mostly from beta-, alphaS1- and alphaS2-casein, with molecular weights between 400 and 1400 daltons. Bioinformatic screening with PeptideRanker and the BIOPEP-UWM database narrowed the field to candidates with predicted activity against multiple targets. Two sequences rose to the top: the tripeptide LRF, predicted to inhibit both alpha-glucosidase and xanthine oxidase, and the seven-residue FLPYPYY, predicted to hit both alpha-glucosidase and DPP-IV.

Molecular docking revealed why these peptides work. FLPYPYY bound alpha-glucosidase with a predicted energy of minus 9.7 kilocalories per mole, anchoring itself through hydrogen bonds to Tyr733, Arg647, Glu767 and Gly766, while LRF formed hydrogen bonds with Asp649, Arg653, Glu788 and Gly766. FLPYPYY also docked into DPP-IV with minus 8.8 kilocalories per mole, engaging Trp629, Trp627 and Tyr547 through pi-pi interactions, and LRF bound xanthine oxidase at minus 7.2 kilocalories per mole. Redocking of co-crystallized ligands produced root-mean-square deviations below 2 angstroms, validating the protocol.

The docking snapshots were then stress-tested in 100-nanosecond molecular dynamics simulations using GROMACS with the Amber99SB-ILDN force field. All four peptide-enzyme complexes stabilized, with backbone RMSD values settling between 0.10 and 0.18 nanometers, radius of gyration and solvent-accessible surface area remaining steady, and free-energy landscapes showing well-defined low-energy basins. MM/PBSA calculations over the final 10 nanoseconds yielded binding free energies of minus 4.16 to minus 23.79 kilocalories per mole, with van der Waals and electrostatic terms favoring association and per-residue decomposition pinpointing energetic hotspots such as Phe735 and Tyr636 in alpha-glucosidase and Arg560 in DPP-IV.

The authors are careful to note the limits of the work. Docking and simulation cannot by themselves prove enzyme inhibition, and the identified peptides still need synthesis, concentration-response testing, IC50 determination and kinetic or structural validation before any functional-food claim can be made. Bioavailability, safety and physiological effects in humans remain open questions. Still, the study demonstrates a compelling pipeline: from a humble carton of goat milk to computationally vetted, dual-target peptide candidates, offering dairy producers a route to higher-value products and offering metabolic-disease researchers a fresh trove of molecules to investigate.

Subject of Research: Multifunctional enzyme-inhibitory peptides generated from goat milk proteins by optimized enzymatic hydrolysis

Article Title: Optimization of enzymatic hydrolysis for generating potential multifunctional peptides from goat milk: Bioactivity evaluation, structural characterization and molecular interaction analysis

Article References: Yu, X., Shu, G., Hu, W., Zhang, G., Xie, P., Song, K., & Li, G. (2026). Optimization of enzymatic hydrolysis for generating potential multifunctional peptides from goat milk: Bioactivity evaluation, structural characterization and molecular interaction analysis. Food Chemistry: X, 39, Article 104517. https://doi.org/10.1016/j.fochx.2026.104517

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104517

Keywords: goat milk, bioactive peptides, enzymatic hydrolysis, alpha-glucosidase, DPP-IV, xanthine oxidase, molecular docking, molecular dynamics, diabetes, hyperuricemia, functional food, response surface methodology