Unraveling Novel γ-Aminobutyric Acid Transaminase (GABA-T) Peptides from Casein: Preparation, Identification, and Its Potential Anxiolytic Mechanism

Food-derived protein peptides with γ-aminobutyric acid transaminase (GABA-T) inhibitory activity possess the promising ability to alleviate anxiety and have become a market focus. This study prepared casein hydrolysate with valid GABA-T inhibitory activity using ultrasound-assisted enzymatic hydrolysis and obtained novel GABA-T inhibitory peptides through isolation and purification. The results demonstrated that ultrasonic pretreatment significantly improved the casein hydrolysis efficiency, enhanced GABA-T inhibitory activity by 19.32%, and allowed retention of 42.37% of the initial inhibitory activity after gastrointestinal digestion. Through peptidomics analysis, five novel GABA-T inhibitory peptides were identified from casein hydrolysate, including FFVAPFPE, VYPFPGPIPN, HLPLPL, FLPYPY, and WQVL (2.79 ± 0.14 to 8.49 ± 0.26 mM). Molecular docking results revealed that these five peptides bind to GABA-T through hydrogen bonds and hydrophobic interactions, with the Arg422 residue potentially serving as the key active site for GABA-T inhibition. This study demonstrates significant potential for both the high-value utilization of casein and the development of antianxiety functional foods targeting GABA-T.