Preparation and Anti-oxidative Effects of Corn Peptides

IntroductionBioactive peptides include the natural peptidesfrom organism itself and the active peptide fromhydrolysate of protein. In the pastfew years,someresearchers have found that small peptides derivedfrom the hydrolysates of food proteins play animportant role in regulating autonomic nervoussystem,activating the cellular immunity function,ameliorating the cardiovascular function,antioxidizing and antiaging,etc.[1— 7] . Smallpeptides prepared from food proteins becomenitrogenous source f…     

Preparation,Antioxidative Effects of Soybean Peptides

In this work an alkaline protease, alcalase, was used to hydrolyze the separated soybean protein at 50℃, pH 8.0. The dependence of hydrolysis time on hydrolysis degree, relative antioxidative activity was examined. The antioxidative activity of the hydrolysate reached the maximum after the hydrolysis for two hours, then decreased. The hydrolysate hydrolyzed for two hours was isolated on a Sephadex G-25 column. The range of molecular weight for the collected fractions was 100-1 300. A fur ther purification of the isolated antioxidative peptides was conducted on a CM-Cellulose column. Two active peaks were observed. One of them was taken to investigate the antioxidative properties for in vitro model systems. It was found that the autoxidation rate of pyrogallol under the alkaline condition was decreased by, at least, 10%, indicating that some free radicals in the tested system were removed. In the experiment of the antihemolysis of erythrocyte, it was observed that the hemolysis degree of erythrocyte caused by hydroxyl free radicals was decreased obviously. This result indicates the protective effect of the antioxidative peptides on the cell membrane damage of erythrocyte. Moreover, it was also found that the membrane fluidity could be depressed after a solution of the antioxidative peptides was mixed with a liposome solution, indicating that the antioxidative peptides could fur ther inhibit the membrane damage caused by lipid peroxidation when the small molecules of antioxidative peptides were embedded in liposome.     

Preparation and Antioxidative Effects of Soybean Peptides*

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Predigestion of soybean proteins with immobilized trypsin for infant formula

Soybean protein isolates of low soybean trypsin inhibitor (STI) residue were prepared by acidic precipitation of soybean flour water extracts (0.8–1.2%) at pH 5.0, followed by acidic washing at this pH and affinity adsorption of residual STI with immobilized trypsin on polystyrene anion-exchange resin GM 201. After heat treatment, soybean protein isolates were subjected to controlled hydrolysis with the immobilized trypsin. Then, the predigested soybean protein was prepared. The predigested soybean protein was free of STI activity, and its solubility at acidic pH range was greatly increased. Sedimentation test showed that it formed a much finer clot at pH 4.5 than that of untreated soybean protein. The pepsin digestibility index at pH 4.0 and chymotrypsin digestibility index at pH 8.0 were obviously improved. These results suggested that the predigested soybean protein prepared by this method may be used in infant formulas.     

Expression and Characterization of a Thermostable Acyl-peptide Releasing Enzyme ST0779 from Sulfolobus tokodaii

Acyl-peptide releasing enzyme(AARE) belongs to a serine peptidase family and catalyzes the NH₂-terminal hydrolysis of N^α-acylpeptides to release N^α-acylated amino acids. ORF0779(ORF=open reading frame) from thermophilic archaea Sulfolobus tokodaii(ST0779) was cloned and expressed in E. coli BL21 and the expressed protein was identified as a thermostable AARE. The target protein could be optimally overexpressed in E. coli at 30 ℃ for 8 h with 0.1 mmol/L isopropyl β-dthiogalactoside(IPTG). The crude enzyme was heated at 70 ℃ for 30 min, and then the target protein could account for above 40% of the total protein. The purification fold was 27 and the enzyme showed both esterase activity and peptidase activity. The optimal temperature and pH for ST0779 were 70 ℃ and 8.0 when Ac-Ala₃ was used as substrate. The half-life of the enzyme(0.2 mg/mL) at 90 ℃ was about 16 h, indicating that the enzyme exhibits a favorable thermostability. The activity of ST0779 could still remain over 85% after being treated at 25 ℃ in different buffers with pH range from 6.0 to10.0 for 24 h, which indicates ST0779 is stable in neutral or slight alkali environment. Under neutral or slightly alkali conditions, the enzyme exhibits really high catalytic efficiency against acyl-peptide, and the optimal substrate is Ac-Ala₃. Most metal ions have no inhibition effect on the activity of ST0779, while 4% activity of ST0779 is inhibited in the presence of K⁺. This enzyme was supposed to be applied in the analysis of protein sequencing and the synthesis of small peptides.     

铈(Ⅲ)-巴比妥钠配合物催化双(对硝基苯基)磷酸酯水解性能

研究了Ce(Ⅲ)离子与巴比妥钠形成的配合物对双(对硝基苯基)磷酸酯(BNPP)的催化水解作用。 结果表明, Ce(Ⅲ)与巴比妥钠形成的配合物对BNPP的水解具有很高的催化活性,可使BNPP水解速率提高至自发水解时的1.52×10⁸倍。 体系的pH值和温度对催化水解反应的影响,发现在温度为25 ℃和pH值为8.50的条件下,催化效果最佳。     

链酚胺型配体锌(Ⅱ)配合物模拟碳酸酐酶研究

合成了酚胺型链状配体,N,N'-二(2-羟基苄基)丙二胺(H~2L)及其Zn(Ⅱ)配合物(ZnL),通过元素分析、IR和^1HNRM等手段进行了表征。采用pH电位滴定法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,测定了配体的质子化常数以及配体与金属离子Zn(Ⅱ)配位反应平衡常数。讨论了配体与金属离子Zn(Ⅱ)的配位情况,得到了配位酚羟基的解离常数。运用分光光度法,在25℃±0.1℃,I=0.1mol·dm^-^3(KNO~3)条件下,在pH=5.5～9.0(50mmol·dm^-^3缓冲溶液)范围内,研究了配合物作为碳酸酐酶模拟物催化对-硝基苯酚乙酸酯(NA)水解动力学,得到了NA酯水解的配合物催化速率常数k~N~P。实验结果表明,ZnHL^+的配位酚羟基的解离常数pK~a为6.83;催化速率常数k~N~P与pH之间不存在Sigmoidal型曲线关系,而是在pH值中性附近有最大值,ZnHL^+对NA酯水解有很好的催化效果,并且采取双重催化机理,是碳酸酐酶很好的模拟物。     

大环三胺1,4,7-三氮杂环癸烷锌(Ⅱ)配合物催化水解作用研究

在25℃、离子强度I=0.10(KNO3)条件下,采用pH电位滴定法测定了大环三胺配体1,4,7-三氮杂环癸烷(TACD)与Zn(Ⅱ)离子的配位平衡常数,讨论了配体与金属离子的配位情况.利用分光光度法,在pH=7～9范围内[2×10-4mol.L-1三羟甲基氨基甲烷(tris)为缓冲溶液]研究了配合物在对硝基苯酚乙酸酯(NA)水解中的催化动力学行为,得到了NA酯的水解速率常数kcat.结果表明,催化水解速率对底物(NA)及配合物浓度均呈一级反应,水解反应遵循速率方程v=(kcat.cZn2++kOH-.cOH-+…).在中性和弱碱性条件下,配合物对NA酯的水解具有很好的催化作用,当pH=9.19时,催化速率常数达3.420×10-2mol-1.L.s-1;催化反应受酸碱平衡控制.     

The Influence of the Extent of Enzymatic Hydrolysis on Antioxidative Properties and ACE-Inhibitory Activities of Protein Hydrolysates from Goby (Zosterisessor ophiocephalus) Muscle

Antioxidant properties and angiotensin-converting enzyme (ACE) inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle, with different degrees of hydrolysis (DH) from 5 to 25 %, prepared by treatment with crude proteases extract from smooth hound intestines, were investigated. Goby protein hydrolysates (GPHs) are rich in Gly and Thr, which accounted for 14.1–15 % and 11.6–13.2 % of the total amino acids, respectively. The antioxidant activities of GPHs were investigated by using several in vitro assay systems. All GPHs exhibited significant metal chelating activity and DPPH free radical-scavenging activity, and inhibited linoleic acid peroxidation. For the ACE-inhibitory activity, as the DH increased, the activity of GPHs increased. The obtained results revealed that antioxidant and ACE-inhibitory activities of GPHs were influenced by the degree of hydrolysis. A medium degree of enzymatic hydrolysis was appropriate to obtain GPHs with good antioxidant activity, while small peptides were essential to obtain high ACE inhibitory activity.     

纳米α-FeOOH催化剂一段法脱除COS和H2S性能的研究

利用均相沉淀法、氨水滴定法制备纳米α-FeOOH粒子，以该粒子为活性组分制备催化剂，利用微反－色谱联用活性评价技术，在常压、空速10 000 h－1、25 ℃～60 ℃温度范围内考察了纳米α-FeOOH催化剂对COS催化水解的活性。采用热重法对纳米α-FeOOH催化剂脱除H2S的性能进行了研究。结果表明：纳米α-FeOOH催化剂对COS水解在低温度、大空速下具有高的活性，系列Ⅰ和系列Ⅱ催化剂分别在60 ℃和40 ℃～45 ℃时COS转化率达到100%。在60 ℃时各种催化剂吸附H2S的能力最强，最高饱和硫容可达到21.72w%。催化剂表面能量分布不均匀，COS催化水解在低温时存在补偿效应。     

pH值对L-抗坏血酸―赖氨酸/甲硫氨酸Maillard反应产物的抗氧化活性的影响

对不同pH值对L-抗坏血酸―赖氨酸/甲硫氨酸模型体系发生的美拉德(Maillard)反应所得到产物(MRPs)的抗氧化性活性的影响进行了研究。结果表明,MRPs的pH值在酸性条件下增大,在碱性条件下减小;在pH=5时,其紫外吸光度、棕色指数、还原力和DPPH自由基清除能力均达到最大;Fe2+螯合能力随着pH值的增大而增大。因此可以得出结论:pH值对抗坏血酸的MRPs的抗氧化活性有较大影响,且在pH=5时,抗坏血酸的Maillard反应产物的抗氧化活性最强。     

两种新稀土双核配合物的合成、表征及其对磷酸二酯键模型物（BDNPP）和DNA的作用研究

合成和表征了两种新的双核配合物[Eu_2 (bbimp) (CH_3COO) (CH_3CH_2O)_2 (CH_3CH_2OH)] (ClO_4)_2 (A)和[Nd_2 (bbimp)-(CH_3COO) (CH_3CH_2O)_2 (CH_3CH_2OH)] (ClO_4)_2 (B)。用紫外光谱法分别研究了磷酸二酯键模型物双-（ 2，4-二硝基苯基）磷酸盐（BDNPP）与配合物（A，B）的水解动力学反应。当 BDNPP与A，B的浓度均为2.5 * 10~(-5) mol/L时，反应为二级反应；在25 ℃，pH 7.26时，二级水解速率常数分别为2479 (mol/L)~(-1)·min~(-1)，1678 (mol/L) ~(-1)·min~(-1)，半衰期分别为16.1 min和23.8 min，比单独的Eu~(3+)，Nd~ (3+)水解BDNPP的速率均快得多，37 ℃时反应更快；在25 ℃，pH 6.50～8.50时， 两个反应的水解速率常数的lgK与pH值均呈正的线性关系。两种配合物与小牛胸腺 （CT）DNA作用，使CT DNA最大吸收峰发生减色和红移，使溴化乙锭（EB）-DNA复 合物体系荧光强度减弱。两种配合物对超螺旋质粒pBR322 DNA的断裂在50 ℃，pH 8.0时，效果最好。     

Interaction of peptides obtained from the enzymatic hydrolysis of soybean meal with cyclodextrins: an evaluation of bitterness reduction

Enzymatic hydrolysis improves the functional and nutritional characteristics of soybean meal proteins. However, the presence of hydrophobic peptides can cause an intense bitterness to the hydrolysate, which is deleterious in terms of final product taste. In this paper we evaluate the interaction of peptides employed for the enzymatic hydrolysis of soybean meal with α-, β- and γ-cyclodextrins, aiming to reduce the bitter taste. Each cyclodextrin was added in mass fractions of 1.5, 2.0 and 2.5% in a hydrolysate of soybean meal prepared with enzyme Alcalase^® 2.4 L at 1% concentration (protein/protein). In order to identify possible interactions between the components, several instrumental techniques were employed. NMR H¹ spectra evidenced strong interactivities between the peptides’ aromatic and aliphatic regions and the cyclodextrins’ internal cavities. Analysis by an electronic tongue system showed that the addition of α- and β-cyclodextrins to the hydrolysate, at concentrations 1.5 and 2.0% (w/w), respectively, induced the greatest difference with regard to control hydrolysate. The difference was also sensory perceptible to untrained tasters in a bitterness ranking test, and reveal that the treatment was efficient in reducing bitterness compared to the control samples, indicating this method as a suitable approach for masking bitterness in soybean hydrolysates.     

Enzymatic Preparation of Bioactive Peptides Exhibiting ACE Inhibitory Activity from Soybean and Velvet Bean: A Systematic Review

The Angiotensin-I-converting enzyme (ACE) is a peptidase with a significant role in the regulation of blood pressure. Within this work, a systematic review on the enzymatic preparation of Angiotensin-I-Converting Enzyme inhibitory (ACEi) peptides is presented. The systematic review is conducted by following PRISMA guidelines. Soybeans and velvet beans are known to have high protein contents that make them suitable as sources of parent proteins for the production of ACEi peptides. Endopeptidase is commonly used in the preparation of soybean-based ACEi peptides, whereas for velvet bean, a combination of both endo- and exopeptidase is frequently used. Soybean glycinin is the preferred substrate for the preparation of ACEi peptides. It contains proline as one of its major amino acids, which exhibits a potent significance in inhibiting ACE. The best enzymatic treatments for producing ACEi peptides from soybean are as follows: proteolytic activity by Protease P (Amano-P from Aspergillus sp.), a temperature of 37 °C, a reaction time of 18 h, pH 8.2, and an E/S ratio of 2%. On the other hand, the best enzymatic conditions for producing peptide hydrolysates with high ACEi activity are through sequential hydrolytic activity by the combination of pepsin-pancreatic, an E/S ratio for each enzyme is 10%, the temperature and reaction time for each proteolysis are 37 °C and 0.74 h, respectively, pH for pepsin is 2.0, whereas for pancreatin it is 7.0. As an underutilized pulse, the studies on the enzymatic hydrolysis of velvet bean proteins in producing ACEi peptides are limited. Conclusively, the activity of soybean-based ACEi peptides is found to depend on their molecular sizes, the amino acid residues, and positions. Hydrophobic amino acids with nonpolar side chains, positively charged, branched, and cyclic or aromatic residues are generally preferred for ACEi peptides.     

黄豆铁蛋白提取新方法及其与豌豆铁蛋白活性比较

铁蛋白是广泛存在于动物、微生物及植物体中的一种铁贮藏蛋白, 具有去除二价铁的毒性以及调节机体细胞铁代谢平衡的作用. 本文以黄豆种子为原料, 开发出黄豆铁蛋白提取新方法, 即将黄豆粗提液在55 ℃下加热15 min, 再将冷却后的上清液分别用500 mmol/L MgCl2和700 mmol/L柠檬酸三钠进行盐析. 离心得到的铁蛋白粗提液经透析后, 用DEAE-cellulose弱阴离子交换层析和Sephacryl S-300凝胶过滤层析进一步分离, 得到电泳纯的铁蛋白. Native-PAGE电泳测得分子量约为560000, SDS-PAGE电泳结果表明, 黄豆铁蛋白含有两种亚基, 分子量分别为28000和26500. 活性研究显示, 黄豆铁蛋白与豌豆铁蛋白铁氧化沉淀和还原释放反应的活性明显不同.     

毛细管区带电泳用于酶微反应器酶解条件的研究

将氨基酰化酶通过戊二醛固定在毛细管内壁,制备毛细管酶微反应器,用毛细管区带电泳对毛细管酶微反应器的酶解产物进行分离,以生成物的峰面积优化底物N-乙酰-DL-蛋氨酸的酶解条件。实验结果表明,在温度37℃的条件下,10μg/mL N-乙酰-DL-蛋氨酸磷酸盐缓冲溶液(pH7.5)以4μL/min的速度通过15 cm长的毛细管酶微反应器,具有良好的酶解效果。利用毛细管酶微反应器对底物N-乙酰-DL-蛋氨酸进行酶解,每天酶解5次,10天后酶活仅下降了8.66%,说明制备的毛细管酶微反应器具有良好的稳定性。     

酸水解法从菊芋中提取果糖

采用热水浸提法提取菊芋中的菊糖,并用磷酸水解为还原糖(大部分为果糖)。从固液比、提取时间、温度、水解时间、温度和菊糖液pH值等方面试验了对还原糖得率的影响,通过正交实验确定了最佳条件为:固液比1∶30,浸提温度80℃,浸提时间30min,水解温度80℃,水解时间30min,pH值为2,可以得到较令人满意的结果。     

超细钴掺杂二氧化钛的制备、表征及气相光催化性能

以四氯化钛为原料、硝酸钴为掺杂剂,制备了粒径10 nm～30 nm的钴掺杂超细二氧化钛并进行了XRD、TEM和FT-IR表征及气相光催化性能的评价。钴掺杂造成了锐钛矿向金红石相的转变温度明显降低,掺杂量从0增加到4%时,相变温度下降了90 ℃左右。制备过程中的pH值对相变也有影响,pH值很小时相变在较低的温度下就能发生。当pH<3,500 ℃焙烧的样品中就基本是金红石型TiO2;红外光谱分析证明掺杂样品比纯样品有更强的吸水性;以苯作为反应物在一个固定床光反应器中考察了钴掺杂二氧化钛的光催化活性。结果表明,钴掺杂对催化剂的光催化性能有影响。反应初期掺杂样品与纯二氧化钛样品相比活性相差不大,但随着反应的进行活性差别逐渐增大。在实验条件下160 min后纯样品基本失活,掺杂样品的活性仍大于50%。     

Specificity of Carboxypeptidases from Actinomucor elegans and Their Debittering Effect on Soybean Protein Hydrolysates

The specificities of carboxypeptidases from Actinomucor elegans were investigated by determining enzymatic activities at pH 7.0 and pH 4.0 with 16 Z-dipeptides and three Z-tripeptides as substrates. The debittering effect was evaluated and the free amino acid compositions of the soybean protein hydrolysates were analyzed before and after treatment with A. elegans extract at pH 7.0 and pH 4.0, with carboxypeptidases from Aspergillus oryzae as control. The results of the enzyme activity determinations indicated that carboxypeptidases from A. elegans prefer hydrophobic substrates, such as Z-Phe-Leu, Z-Phe-Tyr-Leu, and Z-Phe-Tyr. The sensory evaluation and free amino acid composition analysis showed that these carboxypeptidases are efficient tools for decreasing the bitterness of peptides because they liberated the fewest free amino acids, which consisted of 73% hydrophobic amino acids, under acidic conditions. Carboxypeptidases from A. elegans display promising prospects for future applications in the protein hydrolysate industry.     

含阿斯匹林的丙烯酸酯共聚物及其水解

<正> 阿斯匹林是近年来发现具有抗血小板凝聚效应的普通药物。在酯基上含有阿斯匹林基团的亲水性丙烯酸酯聚合物的水解研究表明,这些聚合物有可能作为控制释放阿斯匹林的生物相容性释放体系。本文合成了甲基丙烯酸β-(乙酰水扬酰氧)乙酯(HEMAASA)与甲基丙烯酸(MA)的共聚物,观察其水解行为,以期寻找能够进一步控制释放阿