Krämer Anna C, Torreggiani Armida, Davies Michael J
Department of Biomedical Sciences, Panum Institute, University of Copenhagen , Copenhagen 2200, Denmark.
Istituto per la Sintesi e la Fotoreattivita, ISOF-CNR, Area della Ricerca di Bologna , Via P. Gobetti 101, 40129 Bologna, Italy.
J Agric Food Chem. 2017 Nov 29;65(47):10258-10269. doi: 10.1021/acs.jafc.7b03839. Epub 2017 Nov 14.
Oxidation and heat treatment can initiate changes in the amino acid composition, structure, solubility, hydrophobicity, conformation, function, and susceptibility to proteolysis of proteins. These can result in adverse consequences for mammals, plants, foodstuffs, and pharmaceuticals. This study investigated whether and how individual or combined treatment with heat, a commonly encountered factor in industrial processing, and HO alters the structure and composition of two major milk whey proteins, α-lactalbumin and β-lactoglobulin, and mixtures of these. Thermal treatment induced reducible cross-links in isolated β-lactoglobulin, but not isolated α-lactalbumin under the conditions employed. Cross-linking occurred at lower temperatures and to a greater extent in the presence of low concentrations of HO. HO did not induce cross-linking in the absence of heat. Mixtures of α-lactalbumin and β-lactoglobulin showed similar behavior, except that mixed α-lactalbumin-β-lactoglobulin dimers were detected. Cross-linking was associated with formation of sulfenic acids (RS-OH species), oxidation of methionine residues, cleavage of disulfide bonds in α-lactalbumin, altered conformation of disulfide bonds in β-lactoglobulin, alterations in the fluorescence intensity and maximum emission wavelength of endogenous tryptophan residues, and binding of the hydrophobic probe 8-anilinonaphthalenesulfonate. These data are consistent with increased unfolding and subsequent aggregation of the protein, with these changes being maximized in the presence of both heat and HO. The enhanced aggregation detected with HO is consistent with additional pathways to aggregation above that induced by heat alone. These mechanistic insights provide potential strategies for modulating the extent and nature of protein modification induced by thermal and oxidant treatment.
氧化和热处理可引发蛋白质氨基酸组成、结构、溶解度、疏水性、构象、功能以及对蛋白水解敏感性的变化。这些变化可能对哺乳动物、植物、食品和药物产生不良后果。本研究调查了热（工业加工中常见因素）和过氧化氢单独或联合处理是否以及如何改变两种主要乳清蛋白α-乳白蛋白和β-乳球蛋白及其混合物的结构和组成。在所采用的条件下，热处理可诱导分离的β-乳球蛋白形成可还原交联，但不能诱导分离的α-乳白蛋白形成交联。在较低温度下且在低浓度过氧化氢存在时交联程度更大。在无热的情况下，过氧化氢不会诱导交联。α-乳白蛋白和β-乳球蛋白的混合物表现出类似行为，只是检测到了混合的α-乳白蛋白-β-乳球蛋白二聚体。交联与亚磺酸（RS-OH物种）的形成、甲硫氨酸残基的氧化、α-乳白蛋白中二硫键的断裂、β-乳球蛋白中二硫键构象的改变、内源性色氨酸残基荧光强度和最大发射波长的改变以及疏水探针8-苯胺基萘磺酸盐的结合有关。这些数据与蛋白质展开增加及随后的聚集一致，在热和过氧化氢同时存在时这些变化最大。过氧化氢检测到的增强聚集与热单独诱导的聚集之外的其他聚集途径一致。这些机理见解为调节热和氧化剂处理诱导的蛋白质修饰程度和性质提供了潜在策略。
