Enzymatic modification of sesame seed protein,sourced from waste resource for nutraceutical application

The functional characteristics which include protein solubility at different pH, emulsifying and foaming properties, degree of hydrolysis, molecular weight distribution, antioxidant and ACE inhibitory activity of sesame protein hydrolysates prepared with pepsin, papain and alcalase enzymes were evaluated. The rate of degree of hydrolysis was found to reach maximum (25–30%) within the first time fragment i.e 10 min but 80% of hydrolysis was obtained in 120 min with alcalase. SDS-PAGE of hydrolysates with papain, pepsin and alcalase evinced bands of low molecular weight protein of 14.3 kDa and even lower for alcalase treatment of 120 min. Hydrolysates so formed were of improved functional properties as evident from emulsifying and foaming property. Hydrolysis with different proteases enhanced the protein solubility significantly at pH 7.0. Antioxidative assay revealed radical scavenging activity of the hydrolysates with papain hydrolysates showing maximum antioxidative efficacy. The ultra-filtered peptide fractions which showed comparable ACE inhibitory activity were sequenced by MALDI-TOF and matched to that of previously identified ACE inhibitory peptides. The results corroborate the ACE inhibitory effect of the peptides. Hence, these highly bioactive protein hydrolysates produced from waste sesame meals can be successfully employed in various functional food formulations.     

柠檬酸与胃蛋白酶协同水解牛骨粉的工艺优化

以新鲜牛骨为原料,探讨牛骨粉的制备工艺;采用对比和正交实验相结合的设计方案,用柠檬酸与胃蛋白酶协同水解牛骨粉,以水解度、钙溶出率为特征性指标,三氯乙酸中可溶性氮含量评定水解效果。结果表明:牛骨在121℃,0.14MPa条件下,蒸煮120min全部松软,蛋白质暴露面积增加,有利于其水解;用柠檬酸水解牛骨粉,水解度与钙溶出率呈极显著相关性(P<0.01);柠檬酸与胃蛋白酶协同水解牛骨粉的最佳条件:柠檬酸浓度0.5mol/L、酶与底物蛋白量比(E/S)为500U/g、底物浓度11%、反应时间为6h,水解度与钙溶出率分别达33.7%和11.2%;三氯乙酸中可溶性氮含量达到97.2%,表明大部分产物为低分子肽类,溶解性高。     

Immobilization of pepsin on an acrylamide/2‐hydroxyethyl methacrylate copolymer and its use in casein hydrolysis

Pepsin was immobilized through covalent bonding on a copolymer of acrylamide and 2‐hydroxyethyl methacrylate via the individual and simultaneous activation of both groups. The extent of enzyme coupling upon the activation of both the amino and hydroxyl groups of the copolymer resulted in a synergistic effect. However, the order of activation of the support was critical. The covalently bound enzyme retained more than 50% of its activity even after six cycles. The storage stability of the covalently bound enzyme was 60% after storage for 1 month, whereas the free enzyme lost all of its activity within 10 days of storage at 35°C. The Michaelis constant (K_m) and maximum reaction velocity (V_max) were 1.1 × 10^?6 and 0.87 for the free enzyme and 1.2 × 10^?6 and 0.98 for the covalently bound enzyme when the enzyme concentration was kept constant and the substrate concentration was varied. Similarly, K_m and V_max were 6.73 × 10^?11 and 0.47 for the free enzyme and 7.59 × 10^?11 and 0.545 for the covalently bound enzyme when the substrate concentration was kept constant and the enzyme concentration was varied; this indicated no conformational change during coupling, but the reaction was concentration‐dependent. The hydrolysis of casein was carried out with a fixed‐bed reactor (17 cm × 1 cm). Maximum hydrolysis (90%) was obtained at a 2 cm³/min flow rate at 35°C with a 1 mM casein solution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1544–1549, 2005     

Peptic hydrolysis of bovine beta‐lactoglobulin under microwave treatment reduces its allergenicity in an ex vivo murine allergy model

In this study, the in vivo allergenicity of bovine beta‐lactoglobulin (BLG) in peptic whey protein hydrolysates generated during microwave and conventional heating treatments was assessed. The allergenicity of the hydrolysates was explored by studying the reaction of the murine jejunum from previously immunised Balb/c mice to treated BLG in an Ussing chamber. Intestinal anaphylactic reactions after stimulation of the gut‐associated immune system are a good indicator of potential in vivo allergenicity of whey hydrolysates. Fifty‐two per cent of BLG was hydrolysed by pepsin after only 3 min of microwave irradiation at 200 watts (W), yet it remained intact under conventional heating. Far‐ and near‐UV circular dichroism spectra indicated significant changes in BLG secondary and tertiary structures with microwave irradiation at 200 W. Pepsin whey protein hydrolysates obtained with microwave irradiation at 200 W for 3 min did not stimulate secretion of chloride in the Ussing chamber, as shown by the intensity of the short current values recorded (27.86 μA cm^?2), compared to the conventional pepsin hydrolysates (68.21 μA cm^?2). This demonstrates the low allergenicity of whey protein hydrolysates generated in this manner. These results confirm that microwave treatment combined with peptic hydrolysis could be applied to produce low allergenicity milk peptides.     

Influence of non‐enzymatic glycosylation (glycation) of pea (Pisum sativum) albumins on their enzymatic hydrolysis

The aim of this study was to investigate the influence of non‐enzymatic glycosylation (glycation) on the susceptibility of pea albumins to pepsin hydrolysis. It was proved that the aqueous albumin extract is de facto a nucleo‐glyco‐metalloprotein complex. The non‐enzymatic glycosylation of pea albumins decreased the content of nucleic acids, hexoses and zinc, which bound to this protein. Glycated pea albumins were more susceptible to hydrolysis by pepsin than non‐glycated ones. Copyright © 2005 Society of Chemical Industry     

Isolation and characterization of collagen from bigeye snapper (Priacanthus macracanthus) skin

Acid‐solubilized collagen (ASC) and pepsin‐solubilized collagen (PSC) were isolated from the skin of bigeye snapper (Priacanthus macracanthus) with yields of 64 and 11 g kg^?1 wet weight, respectively. Both ASC and PSC were characterized as type I collagens with no disulfide bonds. Peptide maps of ASC and PSC digested by V8 protease and lysyl endopeptidase showed some differences in peptide patterns and were totally different from those of calf skin collagen. The maximum solubility was observed at pH 4 and 5 for ASC and PSC, respectively. A sharp decrease in solubility of both collagens in acetic acid was found with NaCl concentration above 30 g l^?1. Thermal transitions of ASC and PSC in deionized water were observed with T_max of 30.37 and 30.87 °C, respectively, and were lowered in the presence of acetic acid (0.05 mol kg^?1 solution). Therefore, ASC was a major fraction in bigeye snapper skin and it exhibited some different characteristics to PSC. Copyright © 2005 Society of Chemical Industry     

苦荞蛋白质的低消化性研究Ⅰ——热处理、还原二硫键及添加芦丁对其体外消化率的影响

采用Osborne分级分离的方法从苦荞粉中制备得到清蛋白、球蛋白、醇溶蛋白和谷蛋白。体外消化率测定结果表明,四种蛋白组分的消化率均低于对照-小麦胚分离蛋白和大豆分离蛋白,并且四种组分的体外消化率也存在不同程度的差别:清蛋白最高,谷蛋白最低。热处理可以明显提高苦荞粉四种蛋白组分的体外消化率。添加芦丁不但没有降低四种蛋白组分的体外消化率,反而均有一定程度的提高。二硫键的破坏,除醇溶蛋白得以提高之外,对于其它三种组分只是提高了初始水解速度,最终体外消化率没有明显提高。体外消化实验后,四种蛋白组分所剩的残渣蛋白SDS-PAGE分析结果表明:这些残渣蛋白的谱带存在相似之处:在20kDa处有一条很窄的谱带,在14～10kDa处的谱带较宽。     

吡哌酸锌对实验性胃溃疡的保护作用及其机制

目的: 研究吡哌酸锌对实验性胃溃疡的保护作用及其机制。 方法: 采用大鼠幽门结扎性胃溃疡、大鼠水浸应激性胃溃疡、大鼠乙酸烧灼性胃溃疡和小鼠利血平性胃溃疡四种模型进行实验。每种模型实验动物均衡随机分为 5 组, 即羧甲基纤维素钠(CMC) 阴性对照组、西米替丁(0.5 mg·kg^-1 ) 阳性对照组、吡哌酸锌(0.025、0.05、0.1 g·kg^-1 ) 3 个剂量组(小鼠剂量加倍), 灌胃给药, 每天一次, 连续 5 d,观察药物对实验性胃溃疡的保护作用。同时测定幽门结扎性胃溃疡各组大鼠胃液量、总酸排出量、胃蛋白酶活性和胃壁粘液量。结果: 吡哌酸锌能明显抑制 4 种实验性胃溃疡的形成, 并呈剂量依赖性。 吡哌酸锌 0.1 g·kg^-1剂 量组能 降低 胃液 量 (P<0.05), 吡哌酸锌 0.025、0.05、0.1 g·kg^-1 3 个剂量组均能减少总酸排出量(P<0.01);均能显著降低胃蛋白酶活性(P<0.01), 并显著增加胃壁粘液量(P<0.01)。 结论: 吡哌酸锌对实验性胃溃疡具有保护作用, 其机制与增强胃粘膜保护因素、减少胃粘膜的损伤因素有关。     

抗幽门螺杆菌牛初乳IgG酶解特性的研究(in Vitro)——抗幽门螺杆菌牛初乳IgG抗胃蛋白酶及胃酸屏障的研究

采用幽门螺杆菌全菌抗原免疫妊娠母牛,取牛初乳,离心、过柱得到纯化的免疫球蛋白G(IgG),经非还原态的SDS-PAGE(十二烷基磺酸钠聚丙烯凝胶电泳)和HPLC(高效液相色谱)分析,达到电泳纯和HPLC纯。纯化后的IgG在体外经胃蛋白酶和胃酸处理后,经还原态的SDS-PAGE,HPLC和间接ELISA法检测,结果表明在pH4.5以上的环境中,牛初乳中的抗幽门螺杆菌IgG对胃蛋白酶和胃酸屏障有一定的抗性。     

苦荞蛋白质的低消化性研究Ⅱ——酶解产物的超微结构分析和分子量分布

苦荞麦蛋白质氨基酸组成平衡,生物价高,并且具有独特的生理功能。体外消化实验表明其蛋白质的消化率较低,通过扫描电镜对四种蛋白质组分酶解产物的超微结构进行观察发现,胃蛋白酶作用于四种组分的方式是不同的,胃蛋白酶不仅可以作用与清蛋白和球蛋白的表面,而且随着水解进程的延长胃蛋白酶还可以作用与清蛋白和球蛋白的内部结构,因此其体外消化率相对较高。而对于醇溶蛋白和谷蛋白,其高级结构相对较为稳定,胃蛋白酶只能作用于其表面,很难作用其内部结构,所以这两种蛋白组分的体外消化率相对较低。此外还通过高效液相对其酶解物的分子量分布进行研究,结果表明,清蛋白和球蛋白的酶解产物分子量相对较低,组分多,酶解程度高。醇溶蛋白酶解物的组成较为简单,这可能是由于被胃蛋白酶作用的位点较少所造成的。而谷蛋白,其酶解物的分子量分布广,高分子量的组分所占比例大,这表明其被酶解的程度相对较低。