关键词: 鲣鱼加工副产物；转谷氨酰胺酶；酶法糖基化；抗氧化活性；抗炎活性；食品功能特性

Abstract: To achieve the high-value utilization of skipjack tuna processing by-products and to improve the functional properties of peptides derived from skipjack tuna protein, a tryptic hydrolysate from skipjack tuna dark meat (STEH) was structurally modified by transglutaminase (TGase)-catalyzed glycosylation to obtain peptide-amino sugar conjugates (TG-STEH). A bioactive fraction (300–2 000 Da, TG-STEH-2) was isolated from TG-STEH, and its antioxidant activity was evaluated by various assays. Meanwhile, the anti-inflammatory mechanism of TG-STEH-2 in RAW264.7 macrophages stimulated by lipopolysaccharides (LPS) was elucidated by Western blot and immunofluorescence assays. Experimental results showed that glycosylation significantly improved STEH’s antioxidant potency. Importantly, TG-STEH-2 had no cytotoxicity toward RAW264.7 macrophages at 12.5–100 μg/mL, but significantly inhibited the release of inflammatory cytokines by blocking nuclear factor-kappa B (NF-κB) p65 nuclear translocation and inactivating the NF-κB/mitogen-activated protein kinase (MAPK) (p38/c-Jun N-terminal kinase (JNK)) signaling cascades. Structural characterization revealed that glycosylation triggered conformational rearrangement of peptide chains, optimized molecular mass distribution, and significantly improved the solubility, foaming capacity, emulsifying activity, and water-holding capacity. Overall, this work provides theoretical support for the high-value utilization of skipjack tuna processing by-products and the functional modification of peptides derived from skipjack tuna protein.

Key words: skipjack tuna by-products; transglutaminase; enzymatic glycosylation; antioxidant activity; anti-inflammatory activity; food functional properties