Contributions of molecular size, charge distribution, and specific amino acids to the iron-binding capacity of sea cucumber (Stichopus japonicus) ovum hydrolysates

This study investigated the contributions of molecular size, charge distribution and specific amino acids to the iron-binding capacity of sea cucumber (Stichopus japonicas) ovum hydrolysates (SCOHs), and further explored their iron-binding sites. It was demonstrated that enzyme type and degree of hydrolysis (DH) significantly influenced the iron-binding capacity of the SCOHs. The SCOHs produced by alcalase at a DH of 25.9% possessed the highest iron-binding capacity at 92.1%. As the hydrolysis time increased, the molecular size of the SCOHs decreased, the negative charges increased, and the hydrophilic amino acids were exposed to the surface, facilitating iron binding. Furthermore, the Fourier transform infrared spectra, combined with amino acid composition analysis, revealed that iron bound to the SCOHs primarily through interactions with carboxyl oxygen of Asp, guanidine nitrogen of Arg or nitrogen atoms in imidazole group of His. The formed SCOHs-iron complexes exhibited a fold and crystal structure with spherical particles. (C) 2017 Elsevier Ltd. All rights reserved.

本研究探讨了分子大小、电荷分布和特定氨基酸对海参（刺参）卵水解物（SCOHs）铁结合能力的贡献，并进一步探究了它们的铁结合位点。研究表明，酶的种类和水解度（DH）显著影响SCOHs的铁结合能力。在水解度为25.9%时，由碱性蛋白酶产生的SCOHs具有最高的铁结合能力，达到92.1%。随着水解时间的增加，SCOHs的分子大小减小，负电荷增加，亲水性氨基酸暴露在表面，有利于铁的结合。此外，傅里叶变换红外光谱结合氨基酸组成分析表明，铁主要通过与天冬氨酸的羧基氧、精氨酸的胍基氮或组氨酸的咪唑基氮原子相互作用而与SCOHs结合。形成的SCOHs - 铁复合物呈现出具有球形颗粒的折叠和晶体结构。（C）2017爱思唯尔有限公司。保留所有权利。