The aim of this study was to isolate and identify the peptides with calcium-binding capacity from the different tilapia skin gelatin enzymatic hydrolysates. The complex protease was selected and its hydrolysates were further separated using gel filtration chromatography (Sephadex G-25) and reverse phase high-performance liquid chromatography. Two purified peptides with strong calcium-binding capacity were identified as Tyr-Gly-Thr-Gly-Leu (YGTGL, 509.25 Da) and Leu-Val-Phe-Leu (LVFL, 490.32 Da). The calcium-binding capacities of YGTGL and LVFL reached 76.03 and 79.50 µg/mg, respectively. The structures of the complex of purified peptides and calcium (YGTGL-Ca and LVFL-Ca) were characterized by ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (LC-MS/MS). The results of UV-VIS, SEM, and XRD indicated that YGTGL-Ca and LVFL-Ca were formed as new compounds. The results of FTIR and LC-MS/MS indicated the nitrogen atom of the amino group and the oxygen atom of the carboxyl group in terminates of the peptides provided primary binding sites. Moreover, the hydrophobic amino acids in purified peptides could provide more chelating spaces. This study was of great significance for the development of calcium supplement foods. PRACTICAL APPLICATION: Compared with inorganic calcium and organic calcium, the bioactive gelatin peptide chelated calcium has the characteristics of high utilization rate, high solubility, and high absorption rate. The raw materials are extracted from the tilapia processed waste, which reduce the cost, make full use of resources, and improve the bioavailability. The tilapia skin gelatin peptide calcium chelate can be directly absorbed by the human body, and the absorption efficiency is high, further improving the resource utilization rate and having high economic benefits, which is a comprehensive supplement that can also be used as a functional food.

中文翻译：

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罗非鱼（Oreochromis niloticus）皮肤明胶酶水解产物中具有钙结合能力的肽的鉴定和表征

本研究的目的是从不同的罗非鱼皮明胶酶解产物中分离和鉴定具有钙结合能力的肽。选择复合蛋白酶，并使用凝胶过滤色谱（Sephadex G-25）和反相高效液相色谱进一步分离其水解产物。两种具有强钙结合能力的纯化肽被鉴定为 Tyr-Gly-Thr-Gly-Leu（YGTGL，509.25 Da）和 Leu-Val-Phe-Leu（LVFL，490.32 Da）。YGTGL 和 LVFL 的钙结合能力分别达到 76.03 和 79.50 µg/mg。通过紫外-可见光谱 (UV-VIS)、扫描电子显微镜 (SEM)、X 射线衍射 (XRD)、傅里叶变换红外光谱对纯化肽和钙的复合物 (YGTGL-Ca 和 LVFL-Ca) 的结构进行了表征光谱（FTIR），和质谱 (LC-MS/MS)。UV-VIS、SEM和XRD结果表明YGTGL-Ca和LVFL-Ca是新化合物的形成。FTIR和LC-MS/MS结果表明，肽端的氨基氮原子和羧基氧原子是主要结合位点。此外，纯化肽中的疏水性氨基酸可以提供更多的螯合空间。本研究对开发补钙食品具有重要意义。实际应用：与无机钙和有机钙相比，生物活性明胶肽螯合钙具有利用率高、溶解度高、吸收率高等特点。从罗非鱼加工废料中提取原料，降低成本，充分利用资源，并提高生物利用度。罗非鱼皮明胶肽钙螯合物可直接被人体吸收，吸收效率高，进一步提高了资源利用率，具有较高的经济效益，是一种综合性补充剂，也可作为功能性食品。