谷氨酰胺及其结合肽的研究进展

谷氨酰胺是一种条件必需氨基酸,具有多种生理功能,但是谷氨酰胺单体溶解度低、稳定性差,使其应用受到限制;谷氨酰胺结合肽克服了其单体的缺点并且可以在机体分解而被利用。本文对谷氨酰胺及其结合肽的生理功能、谷氨酰胺结合肽的溶解度、稳定性及生产研究现状进行综述。     

谷氨酰胺结合肽组成及贮藏稳定性研究

利用高效液相色谱法(HPLC)测定谷氨酰胺含量,对应用胰蛋白酶和Protamex复合酶双酶组合水解豆粕蛋白制备谷氨酰胺结合肽(Gln)的组成和贮藏稳定性进行研究。将谷氨酰胺肽进行分子量分布测定、不同贮藏条件下贮藏稳定性试验,以及85℃、6周的加速试验。研究结果表明,谷氨酰胺肽初产物中分子量分布大部分在1 000 Da以下,约70%集中在500 Da~132 Da之间,只有不到10%分布在132 Da以下,谷氨酰胺的含量是6.938 7%;粉末4℃和室温(25℃)、溶液4℃和室温(25℃)恒湿密封贮藏,Gln的水解率分别为2.870 9%、3.116 4%、3.264 9%、3.309 7%;经过85℃、6周的加速试验,Gln的水解率为8.156 1%。     

谷氨酰胺酶在10 t规模酱油发酵中应用研究

鲜味是反映酿造酱油品质的一项重要指标。谷氨酰胺酶可以催化谷氨酰胺生成谷氨酸和γ-谷氨酰肽,从而提高酱油的鲜味。文章研究了在10 t规模酱油发酵过程中添加谷氨酰胺酶对酱油中谷氨酸、谷氨酰胺、γ-谷氨酰肽、氨基酸态氮和全氮等指标的影响,并对添加谷氨酰胺酶的酱油进行了HS-SPME-GC-MS分析和感官评定。结果表明,添加谷氨酰胺酶可明显提高酱油原油的谷氨酸含量、氨基酸态氮含量、全氮含量并调节γ-谷氨酰肽的种类及含量。添加谷氨酰胺酶对酱油原油的pH值和总酸含量有小幅度影响。HS-SPME-GC-MS分析表明,添加谷氨酰胺酶的酱油的挥发性风味物质发生了一定变化,醇类、醛类、酮类化合物的种类和含量都有所增加,使酱油的滋味和气味更加丰富。感官评价显示添加谷氨酰胺酶可较大幅度提升酱油的鲜味强度,小幅度减弱酱油的苦味和增加酱油的酸味,对咸味、甜味的影响较小。该研究结果为谷氨酰胺酶在酱油酿造中的应用提供了理论支持。     

不同来源谷朊粉谷氨酰胺肽释放特性的比较分析

从国内谷朊粉生产厂家收集了12种商品谷朊粉,在对其进行基本组成分析基础上,研究了不同来源谷朊粉的酶解及谷氨酰胺肽释放特性。结果表明：所收集谷朊粉样品的蛋白质平均含量为77.59%,样品间差异较小（CV:2.68%）;淀粉含量差异较显著（CV:21.65%）;脂肪含量虽然较低（平均1.08%）,但样品间差异较大（CV:69.60%）;氨基酸组成中谷氨酸/谷氨酰胺平均含量较高,为412.58 mg/g蛋白,占总氨基酸组成的39.38%。综合考虑不同样品酶解产物中蛋白回收率、水解度及谷氨酰胺含量三个指标,以获得高谷氨酰胺含量的短肽为目的,最终确定1号（山东滨州）、9号（陕西宝鸡）、12号（河北邢台）样品为制备谷氨酰胺肽的理想原料,这三种样品的酶解产物中有效谷氨酰胺含量可达22%左右,水解度大于15%,蛋白回收率大于90%。     

小麦低聚肽粉中谷氨酰胺含量测定方法及其临床应用前景

采用BTI-AQC二步柱前衍生法建立了一种有效检测小麦低聚肽粉中谷氨酰胺含量的方法。该方法在2～100μmol/L谷氨酰胺浓度内有很好的线性关系(r~2=0.999 9),最低检出限为2μmol/L,所有标准品3次重复的衍生峰面积相对标准偏差RSD均<1%,最适条件下标准二肽AQ(Ala-Gln)的检测回收率为(95.94±0.22)%。该方法检测小麦低聚肽粉中Gln含量为(23.54±0.49)%,远高于其他常见食源性低聚肽类产品。测定结果显示,除具有高的谷氨酰胺含量外,小麦低聚肽粉还具有水溶性好、稳定性强、易于消化吸收、蛋白含量高、氨基酸组成均衡等优势。     

BTI保护法测定小麦水解蛋白中谷氨酰胺含量

根据蛋白中谷氨酰胺与BTI试剂反应后不再被酸解转化为谷氨酸的原理,介绍了测定蛋白质和肽中谷氨酰胺方法,主要包括样品的BTI处理、酸解、PITC衍生和HPLC色谱分析等。以小麦水解蛋白为例,测定结果为:结合态谷氨酰胺质量分数为(26.178±0.061)%,游离谷氨酰胺质量分数为(0.121±0.008)%,其他17种游离氨基酸质量分数为(2.053±0.034)%。丙氨酰-谷氨酰胺二肽标准品和游离氨基酸含量测定结果印证了该方法是可靠的,可测定蛋白质和肽分子中的谷氨酰胺含量。     

小麦低聚肽和谷氨酰胺对大鼠胃肠黏膜损伤的保护作用

观察灌胃小麦低聚肽和谷氨酰胺对非甾体类药物(NSAIDs)致大鼠胃肠黏膜损伤的保护作用。挑选70只SD大鼠随机分为空白对照组、损伤组及低、中、高剂量小麦低聚肽组[灌胃剂量分别为20、100、500 mg/(kg·d)]和小麦蛋白组、谷氨酰胺组[灌胃剂量均为20 mg/(kg·d)]。每天灌胃1次,连续灌胃30 d。大鼠处死前,用非甾体类药物灌胃损伤大鼠胃肠2次。取大鼠血清、胃和小肠黏膜组织,观察血清细胞因子、胃肠病理切片、小肠黏膜抗氧化酶和阿片受体mRNA表达的变化。结果显示非甾体类药物可以显著增加小肠黏膜的氧化应激水平,小麦低聚肽能上调小肠黏膜中GSH-Px的活力,具有一定的抗氧化功能,能够减轻胃肠黏膜损伤。小麦低聚肽还可以显著降低了血清中TNF-α含量,下调mu-阿片受体mRNA的表达。说明非甾体类药物可以诱导大鼠胃肠黏膜损伤的模型,小麦低聚肽可以有效减少大鼠胃肠黏膜损伤。低剂量小麦低聚肽组作用最强,效果优于谷氨酰胺组。     

富含谷氨酰胺多肽的制备及其体外模拟消化

以乳清蛋白、大米蛋白和小麦蛋白为原料,通过不同酶水解制备富含谷氨酰胺多肽,根据蛋白质回收率、酰胺氮含量、分子质量分布以及抗氧化活性(羟自由基清除活性和氧自由基吸收能力)筛选不同来源的最优多肽。研究优选的3种多肽耐受胃肠模拟消化能力,确定其制剂形态并筛选富含谷氨酰胺多肽制备的最优原料。结果显示,乳清蛋白肽(胰蛋白酶组)、大米蛋白肽(风味蛋白酶组)及小麦蛋白肽(风味蛋白酶组)为优选多肽,作为模拟消化的研究对象。以乳清蛋白肽为基料的谷氨酰胺功能性食品,应选择肠溶胶囊为包装材料。大米蛋白肽、小麦蛋白肽采用普通胶囊为包装材料。小麦蛋白肽经胃肠模拟消化后酰胺氮含量增至1.90%,小分子肽(Mw 1 ku)占比高达74.59%,且抗氧化活性无显著差异(羟自由基清除率为22.89%,ORAC值为1.28μmol TE/(L·mg)肽,P 0.05),说明小麦蛋白是制备富含谷氨酰胺多肽的最优原料。     

水解面筋蛋白高效制备谷氨酰胺结合肽的研究

采用食品级胃蛋白酶、胰蛋白酶、Protamex复合酶双酶组合对面筋蛋白进行水解制备Gln结合肽。先确定三种单酶各自对面筋蛋白适宜的初始pH、温度、酶浓度和底物浓度。并以双酶进行两两组合水解。在进行水解度控制实验时取样,分析水解液中氨基氮的含量,计算平均肽链长度,并用高效液相色谱分析水解液中Gln的得率。实验结果表明胰蛋白酶和胃蛋白酶联合水解的效果最好,条件为:胰蛋白酶在pH8.0,50℃,S%=12.8%(W/V),E%=9%(W/W)水解6h,再用胃蛋白酶pH2.0,40℃,E%=5%(W/W)条件下水解5h,可得到平均肽链长度为2.20个氨基酸残基的蛋白水解液,Gln得率最高,为60.43%。认为胰蛋白酶和胃蛋白酶组合是面筋蛋白中高效制备谷氨酰胺结合肽的最佳组合。     

小麦低聚肽抗氧化活性研究

目的:对小麦低聚肽抗氧化活性进行研究。方法:选取小麦低聚肽中的11个2~4肽的肽段和谷氨酰胺氨基酸,利用AAPH作为氧自由基来源,Sodium Fluorescein为荧光指示剂,VE水溶性类似物Trolox为定量标准,使用荧光酶标仪分析小麦肽段的抗氧化能力。结果:小麦低聚肽具有清除脂质过氧化自由基的能力。结论:小麦低聚肽具有较好的抗氧化活性,是开发相关保健食品的重要资源。     

Effect of glutamine peptide on baking characteristics of bread using experimental design

 Glutamine is a conditionally essential amino acid as a deficit in this residue occurs during periods of catabolic stress. Glutamine-containing peptides can therefore be considered as potential functional food ingredients. The ubiquitous nature and low cost of bread makes it a potentially ideal vehicle for the delivery of glutamine peptide to the body. Glutamine-enriched peptide products were obtained following enzymatic hydrolysis of gluten. When glutamine peptide is incorporated into bakery products the processing variables considered optimal for standard bread result in dough with poor machinability. To optimize the production process a central composite design was chosen. Water addition, mix time, rest time and proof time were chosen as predictor variables. Each experiment was evaluated based on baking tests, color measurements and texture analysis. Production processes for standard bread and bread containing glutamine peptide at 3% w/w were compared. Mix time was a major influence on the baking characteristics of bread containing glutamine peptide and standard bread. Slight deviations from the optimum resulted in substantial increases in moisture loss and decreases in volume. Texture values in standard bread were strongly influenced by water addition. Using experimental design a production process resulting in high quality bread containing glutamine peptide was developed. Received: 21 February 2000 / Revised version: 28 April 2000     

NITROGEN FERTILIZATION AND THE FORMATION OF 2-PYRROLIDONE-5-CARBOXYLIC ACID IN STORED AND PROCESSED TABLE BEETS

SUMMARY —The conversion of glutamine to the bitter compound, 2-pyrrolidone-5-carboxylic acid (PCA), in table beets was studied. Glutamine was analyzed by a phosphate-buffer hydrolysis and distillation method. PCA was extracted with ethyl acetate and the ditrimethylsilyl derivative prepared and measured quantitatively by gas-liquid chromatography. The accumulation of glutamine in fresh beets with excessive amounts of nitrogen fertilization caused a substantial increase in PCA content of processed beets. Conversion of glutamine to PCA in beets was proportional to the heating time during processing. Glutamine content did not alter during raw beet storage periods at 35°F; PCA content increased gradually.     

VOLATILE NITROGEN-CONTAINING COMPOUNDS GENERATED FROM MAILLARD REACTIONS UNDER SIMULATED DEEP-FAT FRYING CONDITIONS

A total of 29 volatile nitrogen-containing compounds were identified from model systems containing glutamine, glutamic acid, asparagine and aspartic acid, respectively, with glucose under simulated deep-fat frying conditions in corn oil. Alkylpyrazines were the most important flavor compound generated. Glutamine, which released free ammonia easily under this condition gave the highest yield of alkylpyrazines. The profiles of pyrazines produced by each amino acid were significantly different. In a glutamine system, 2-(2-furyl)pyrazine, 2-(2-furyl)- 5-methylpyrazine and 2-(2-furyl)-6-methylpyrazine were the major compounds generated.     

Pre‐existent Hsp72 contributes to glutamine‐induced hepatic hsp72 gene activation during heat shock recovery period in rat

Scope Functional maintenance of liver is very important at all times for personal health. Hsp induction is associated with the protection of the organ. Glutamine, a nutrient inducer of Hsps, enhances cellular survival via Hsp72 induction in several organs, but not in the liver. The present study showed a novel approach to facilitate glutamine‐induced hepatic Hsp72 synthesis and its possible mechanisms were discussed. Methods and results Sprague‐Dawley rats were used as the experimental animals and the livers were the targets. Glutamine was administered via tail‐vein injection, and its effects on hsp72 gene activation, including Hsp72 expression, heat shock factor‐1 (HSF‐1) phosphorylation and DNA‐binding activation, were evaluated. The results showed that Hsp72 itself played a critical role in glutamine‐induced hepatic Hsp72 synthesis during HS recovery period in a dose‐dependent manner of preexistent Hsp72. The peak value of HSF‐1 phosphorylation, HSF‐1 DNA‐binding activity, hsp72 mRNA accumulation, and Hsp72 synthesis was detected at 8 h after glutamine administration. Conclusion Glutamine switched on alteration pathway in inducing hsp72 gene activation. The existence of Hsp72 plays a critical role in the reactivation of hsp72 gene. Glutamine sustained the induction of intracellular Hsp72, which could be beneficial in protecting the liver from various injuries.     

谷氨酰胺对运动能力影响的研究进展

谷氨酰胺是人或哺乳动物体内含量最丰富的一种游离的条件必需氨基酸, 是机体内众多代谢活动的能量来源, 对机体各器官功能的正常发挥起着重要的作用。但是在应激状态下, 谷氨酰胺的供求平衡会被打破。谷氨酰胺因其独特且复杂的生理特性成为营养学、生理学、生物化学、运动医学等多领域的研究热点。随着国际竞技体育的蓬勃发展, 功能性运动补充剂不断被开发, 在此期间谷氨酰胺在运动能力提升方面的巨大潜力被发掘, 经过研究发现谷氨酰胺能够有效提高机体运动能力并延缓疲劳。本文对过度运动与谷氨酰胺之间的关系及谷氨酰胺的生理功效进行综述, 并对谷氨酰胺未来的研究方向进行展望。     

谷氨酰胺及其二肽的营养生理研究进展

谷氨酰胺（Ｇｌｎ）因其对人和动物的重要生理作用而引起广泛关注,大量的证据表明谷氨酰胺是一种十分重要的具有特殊营养作用的条件必需氨基酸。但由于它的不稳定性及低溶解度,使其应用受到限制,谷氨酰胺二肽克服了它的缺点并可被分解为氨基酸而被利用,且无任何毒副作用和不良反应。综述了谷氨酰胺及其二肽的营养生理作用研究进展。     

UPLC快速测定可溶性肽或蛋白中谷氨酰胺含量

建立了UPLC测定谷氨酰胺的方法。采用BTI([bis(trifluoroacetoxy)iodo]benzene,BTI)衍生化肽或蛋白中非氮端的谷氨酰胺(Glutamine,Gln),衍生产物L-2,4-二氨基丁酸(L-2,4-Diaminobutyric acid,DABA)经2,4-二硝基氟苯(2,4-Dinitrofluorobenzene,DNFB)紫外显色后,用超高效液相色谱仪(UPLC)在355nm下进行检测测定。结果表明,DABA的最低检出限为0.2ng/mL,线性范围为1～10μg/mL。经Ala-Gln、β-乳球蛋白、α-乳清蛋白和溶菌酶四种蛋白标品检验,测得标样中Gln的回收率为93%±2%～98%±3%。所用方法具有检出限低、样品用量少、高效快速等特点。