猪皮胶原蛋白水解物体外抗氧化作用模式初探

通过测定不同浓度不同水解时间的猪皮胶原蛋白水解物的还原能力、清除自由基能力、抗脂质氧化能力、金属离子鳌合能力来探讨其体外抗氧化作用机制。结果表明:在一定水解范围内,猪皮胶原蛋白水解物的抗氧化活性随着底物浓度的增加而增加,且水解物的还原能力、自由基清除能力、抗脂质氧化能力及Cu2+和Fe2+鳌合能力均随水解时间的延长而增大;底物浓度为4%、水解6 h的猪皮胶原蛋白水解物与其他水解条件下的水解物相比,具有较高的抗脂质氧化能力和较强的清除自由基能力,且具有丁基羟基甲苯(butylated hydroxytolu-ene,BHT)、抗坏血酸(ascorbic acid,Vc)等抗氧化剂所不具备的金属鳌合能力;4%的猪皮胶原蛋白6h水解物与0.02%Vc的还原能力相近。猪皮胶原蛋白水解物具有较高的抗氧化活性,可以作为氢供体、自由基稳定剂和金属离子螯合剂来抑制脂肪氧化。     

金花茶花浸提物与消化蛋白酶的相互作用

为探讨金花茶花浸提物对消化蛋白酶活性的影响及其作用机理,首先研究了金花茶花浸提物对消化蛋白酶活性的影响以及抑制动力学,其次采用荧光光谱法、紫外光谱法和圆二色谱法研究浸提物抑制消化蛋白酶活性的机制。结果表明,醇提物和水提物对胃蛋白酶(IC₅₀分别为3.194和3.330 g/L;竞争抑制常数分别为4.518和7.641 g/L)和胰蛋白酶(IC₅₀分别为29.131和56.534 g/L;竞争抑制常数分别为74.571和175.832 g/L)有明显的抑制作用,且抑制类型为混合型抑制;金花茶花浸提物能降低胃蛋白酶(猝灭常数分别为1.522和1.205 L/g)和胰蛋白酶(猝灭常数分别为2.175和1.392 L/g)的内源荧光,改变消化蛋白酶的二级结构。因此,金花茶花浸提物可通过改变消化蛋白酶的结构抑制其活性,该研究为金花茶花功能性食品开发提供理论支撑。     

大分子拥挤环境下多糖对蛋白肽的修饰研究

采用胃蛋白酶适度水解大豆分离蛋白得到蛋白肽,在大分子拥挤环境下通过Maillard反应制备蛋白肽-葡聚糖共价复合物(Hydrolated Soy Protein Isolated-Dextran Conjugates,HDC),采用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)技术证实大豆7S球蛋白和葡聚糖发生了共价结合,并通过乳化剪切机、荧光分光光度计、差示扫描量热仪和粒度分布仪等对其接枝度、溶解性、热稳定性、抗氧化性和乳化性能进行系统分析。结果表明:大分子拥挤环境下大豆水解蛋白肽-葡聚糖60℃反应4 h就可以形成较高接枝度的共价复合物,溶解性较大豆分离蛋白(Soybean protein isolated,SPI)和大豆分离蛋白-葡聚糖(Soybean Protein Isolated-Dextran Conjugates,SDC)有所提高,热稳定性好,HDC的自由基清除率明显高于大豆水解蛋白和它与葡聚糖的混合物,达到66.39%,且羟自由基清除率高于维生素C,HDC的乳液粒径最小并具有优越的乳化稳定性。     

Transformation of antimicrobial into bradykinin‐potentiating peptides during peptic hydrolysis of bovine haemoglobin: identification,release kinetics and reaction network of peptides

The precursor cleavage of the antimicrobial peptide α107–136 into the bradykinin‐potentiating peptide α110–125 during peptic hydrolysis of bovine haemoglobin was investigated by reverse phase high‐performance liquid chromatography coupled with tandem mass spectrometry. The optimal conditions for the preparation of α107–136 and α110–125 were found to be low and high degrees of hydrolysis respectively. A total of six peptides were identified as being involved in the cleavage process. Moreover, the reaction network of these peptides was developed according to the sequence alignment and their release kinetics. The affinity of pepsin towards different peptide bonds of bovine haemoglobin was also compared based on data from the release kinetics of peptides. In addition, some potentially bioactive peptides were predicted by means of sequence analysis and secondary structure calculations. Copyright © 2006 Society of Chemical Industry     

水解动物蛋白(HAP)的酶法制备及应用

报道了畜禽肉及鱼用酶解法制备ＨＡＰ的最适条件。当用双酶水解时，先用胰蛋白酶后用胃蛋白酶，水解效果最好。酶—酸联合水解，胶体磨处理及热变性，都能提高蛋白质水解率。ＨＡＰ有广泛应用前景。     

伴大豆球蛋白胃蛋白酶水解肽对双歧杆菌增殖的影响

大豆种子的贮藏蛋白主要由2种球蛋白组成,伴大豆球蛋白(conglycinin)是其中一种,它由3个不同的亚基组成。文中对伴大豆球蛋白进行了分离纯化,并研究了其体外经过胃蛋白酶水解后的肽对双歧杆菌增殖的影响。结果表明,分离纯化的伴大豆球蛋白纯度为90.13％,可供生理功能的研究,经胃蛋白酶水解后的肽能够促进双歧杆菌的增殖,表现出一定的生物活性作用。     

Pepsin-induced changes in the size and molecular weight distribution of bovine casein during enzymatic hydrolysis

Bovine casein was digested with pepsin at pH 2.0 in a batch-stirred tank reactor. To investigate the effect of peptic digestion on the aggregate size and molecular weight distribution of bovine casein, the resulting hydrolysates were examined by size-exclusion chromatography coupled with multiangle laser light scattering and dynamic light scattering. Casein was resolved by size-exclusion chromatography into 2 major peaks corresponding to aggregates and monomers, both of which showed a continuous decrease as hydrolysis proceeded. However, the ratio of aggregates to monomers was maintained at almost 1 (2:2.5) during the initial 30-min hydrolysis, indicating that the caseins in solution were in a type of equilibrium between aggregates and monomers. Upon peptic hydrolysis, casein aggregates increased in size and molecular weight, and exhibited a decrease in intermolecular repulsion. This finding was confirmed by dynamic light scattering measurements, which traced the changes in the hydrodynamic radii and light scattering intensities of casein hydrolysates. In addition, the release kinetics of peptide fractions with different molecular weights was also examined. It was concluded that the increase in hydrophobic attraction and the reduction in intermicellar repulsion might promote the growth in aggregate size of bovine casein during the limited hydrolysis.     

Effect of pH and Pepsin Limited Hydrolysis on the Structure and Functional Properties of Soybean Protein Hydrolysates

Effects of limited enzymatic hydrolysis with pepsin on the functional properties and structure characteristics of soybean proteins were investigated. Hydrolysates with different incubation time (10 to 900 min) were prepared. Results showed that SPI hydrolyzed for 60 min exhibited the best emulsibility and the ability of resisting freezing/thawing. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis proved that pepsin can degrade glycinin but had little effect on the α’ subunit of β‐conglycinin. The structure unfolding reached the largest extent after incubation for 60 min and the soluble and flexible aggregates were formed. After 120 min, glycinin was degraded totally and β‐conglycinin formed insoluble aggregates. Moreover, 2 methods were applied for the deactivation of pepsin to obtain final hydrolysates at pH 2.0 and 7.0, respectively. The structure analysis revealed that the unfolding extent and structure characteristic were different in these 2 conditions. When adjusting the pH value from 2.0 to 7.0, the unfolding protein molecular would reaggregate again at pH 7.0 due to the charge neutralization, and the hydrodynamic diameter and λ_max absorbance decreased compared to pH 2.0. Moreover, some of the insoluble aggregates formed at pH 2.0 became soluble at pH 7.0, because of the salt‐in phenomenon.     

黄鲫胃蛋白酶酶解液体外抗氧化、抑菌作用研究

采用胃蛋白酶水解黄鲫,测定酶解液的蛋白提取率、可溶性肽含量、水解度及氨基酸组成,并对酶解液体外抗氧化和抑菌作用进行研究。结果表明：黄鲫胃蛋白酶酶解液的蛋白提取率、可溶性肽提取率、水解度分别为 (110.28 ± 4.81)%、(81.78 ± 0.04)% 和 (18.12 ± 0.39)%,黄鲫胃蛋白酶酶解液的人体必需氨基酸相对含量可达37.91%。黄鲫胃蛋白酶酶解液具有很强的抗氧化能力,清除羟自由基和DPPH 自由基的ED50 分别为4.55μg/mL 和4.46μg/mL,还原力随着黄鲫胃蛋白酶酶解液质量浓度的增加而增大,在3.4 μg/mL 和13.6μg/mL 低、中质量浓度时螯合金属离子能力与EDTA 接近。体外抑菌实验显示：黄鲫胃蛋白酶酶解液具有广谱抑菌性,对大肠杆菌的抑菌效力分别与 13.21～15.44mcg/mL 的氨苄青霉素和 325.00～340.00U/mL 的硫酸链霉素相当 (P ＞ 0.05)。