In silico identification of novel small molecule umami peptide from ovotransferrin

Umami ingredients are the important components of seasoning in food and widely used in food production. However, few novel umami peptides were isolated and identified. Here, the purpose of this research is to identify small molecule umami peptides derived from ovotransferrin by molecular docking. Based on the virtual enzymatic hydrolysis and molecular docking analysis, the tripeptide DEK with the lowest CDOCKER-ENERGY (−99.50 kcal mol⁻¹) was identified, which could occupy the extracellular venus flytrap domain (VFTD) of T1R1/T1R3 (taste receptor type 1, member 1 and 3). Furthermore, the electronic tongue was used to measure the umami taste of DEK. The results showed that the umami value of DEK was 2.31, which was higher than that of monosodium L-glutamate via electronic tongue analysis. The docking results showed that virtual screening and molecular docking may be a more reliable and rapid method to substitute for classical methods for screening and identification of small molecule umami peptides.     

“厚味”γ-谷氨酰-缬氨酸增味作用差异性机制

γ-谷氨酰-缬氨酸（γ-Glu-Val）具有多变的呈味特性,在水溶液中呈现涩味,可以增强基本味觉物质的味感强度,赋予奶酪、鸡汤、酱油等食物厚味味感。目前对于γ-Glu-Val呈味特性的机理研究甚少,尤其是鲜见它对于味觉增强效果的差异性机制的研究。本实验利用感官实验和分子模拟对γ-Glu-Val增味作用的差异性机制进行研究。感官实验结果显示,γ-Glu-Val对于基本味感（鲜味、甜味、咸味和酸味）均有一定的提升作用,而对于鲜味的提升效果最为明显。分子模拟实验的结果表明,γ-Glu-Val对基本味感受体（T1R1、T1R2和T1R3）均有一定的亲和力,其中对于鲜味受体T1R1的亲和力最强、结合自由能最高,与此相反,γ-Glu-Val对甜味受体T1R2的亲和力最弱、结合自由能最低,暗示其增鲜作用强于增甜作用。分子动力学结果显示,在味精存在的前提下,γ-Glu-Val可通过氢键和疏水键与鲜味受体T1R1上的氨基酸残基（Phe-274、Ser-275、Ser-300、Trp-303、Ala-147、Ala-170）相互作用,激活鲜味受体,以实现其增鲜作用。本实验解析了γ-Glu-Val增味作用差异性分子机制,为进一步验证其呈味机理提供理论支撑;同时为小分子物质的增味作用研究提供了思路。     

A review of the associations between single nucleotide polymorphisms in taste receptors,eating behaviors,and health

Food preferences and dietary habits are heavily influenced by taste perception. There is growing interest in characterizing taste preferences based on genetic variation. Genetic differences in the ability to perceive key tastes may impact eating behavior and nutritional intake. Therefore, increased understanding of taste biology and genetics may lead to new personalized strategies, which may prevent or influence the trajectory of chronic disease risk. Recent advances show that single nucleotide polymorphisms (SNPs) in the CD36 fat taste receptor are linked to differences in fat perception, fat preference, and chronic-disease biomarkers. Genetic variation in the sweet taste receptor T1R2 has been shown to alter sweet taste preferences, eating behaviors, and risk of dental caries. Polymorphisms in the bitter taste receptor T2R38 have been shown to influence taste for brassica vegetables. Individuals that intensely taste the bitterness of brassica vegetables (“supertasters”) may avoid vegetable consumption and compensate by increasing their consumption of sweet and fatty foods, which may increase risk for chronic disease. Emerging evidence also suggests that the role of genetics in taste perception may be more impactful in children due to the lack of cultural influence compared to adults. This review examines the current knowledge of SNPs in taste receptors associated with fat, sweet, bitter, umami, and salt taste modalities and their contributions to food preferences, and chronic disease. Overall, these SNPs demonstrate the potential to influence food preferences and consequently health.     

基于STC-1细胞味觉感知模型对鱼露脯氨酸二肽呈鲜特性的研究

为探究鱼露中脯氨酸二肽的呈鲜特性,本研究以感官评价为基础,建立STC-1小鼠小肠内分泌细胞味觉感知模型,采用钙离子成像方法反映脯氨酸二肽的呈味剂量效应,通过实时荧光定量PCR技术测定二肽对鲜味受体T1R1、T1R3、CaSR、GPRC6a的mRNA表达量的影响,判断介导二肽呈鲜的主要受体。结果表明:13个脯氨酸二肽均无苦味,多呈鲜味和酸味,呈味较强的肽同时具有较低的阈值,其中具有较强味觉活性的肽为Ser-Pro、Ala-Pro、Pro-Ala、Pro-Val、Pro-Ile。脯氨酸二肽的呈味活性越强,其对鲜味受体mRNA表达的促进程度越强,推测T1R1是介导脯氨酸二肽呈鲜的重要受体。本研究提供了一种鱼露脯氨酸二肽呈鲜特性的非人工感官评价方法,同时为深入研究鱼露寡肽呈鲜的定量构效关系打下基础。     

Potential effects of umami ingredients on human health: Pros and cons

Abstract

Umami taste is the most recent confirmed basic taste in addition to sour, sweet, bitter, and salty. It has been controversial because of its effects on human nutritional benefit. Based on the available literatures, this review categorized 13 positive and negative effects of umami taste on human health. On the positive side, umami taste can improve food flavor and consumption, improve nutrition intake of the elderly and patients, protect against duodenal cancer, reduce ingestion of sodium chloride, decrease consumption of fat, and improve oral functions. On the other hand, umami taste can also induce hepatotoxicity, cause asthma, induce migraine headaches, damage the nervous system, and promote obesity. Due to its novelty, there are many functions and effects of umami taste waiting to be discovered. With further investigation, more information regarding the effects of umami taste on human health will be discerned.     

Interactions between umami and other flavor characteristics

Our understanding of the taste transduction mechanisms of umami substances is still in its infancy. However, evidence is now emerging that suggests that umami taste is perceived according to a receptor-mediated mechanism similar to those for sweet and bitter tastes. The synergistic interactions between glutamate and nucleotides appear to arise from an allosteric effect of nucleotides on a glutamate receptor. In some foods, umami substances appear to enhance the perceived sweetness or saltiness, or other flavor characteristics such as thickness and complexity, which may contribute to the ability of umami substances to improve overall palatability in certain foods.     

味觉受体及其传感器研究与应用

中国传统饮食和食品的烹制与加工讲究色、香、味俱全,其中"酸、甜、苦、辣、咸五味调和"又构成其核心标准。国际上也分为"五味",分别为"酸、甜、苦、咸、鲜",其中少了辣味,多了鲜味。也有人建议将脂肪的味道定义为"香"味,但是中国人的"香"实际上是"香气",属于嗅觉,而非味觉。大量研究证明,多数味觉受体作为营养传感系统,如苦、甜、鲜都属于G蛋白偶联受体超家族成员,而且其分布并不限于味蕾、肠道等,其他组织均有分布,是药物筛选的重要靶标。然而,到目前为止,市场上进行味觉测定仍然依赖于电子鼻和电子舌等仪器设备,味觉受体传感器及其有关技术则仍处于探索和研究阶段。其主要原因是:味觉受体和其他大多数受体一样,在与配体识别和启动信号传递时主要依赖于弱相互作用,如何将这些弱相互作用转变为传感器可以处理并放大的光、声、电、磁、热等信号,从而实现其定量测定是一个关键性难题。但是,由于味觉受体在医药筛选、食品添加剂、食品的功能性评价和代谢综合征预防等方面的巨大应用与开发前景,其检测方法一直是科学家关注的焦点之一。本文将针对味觉受体及其传感器检测技术的研究进展进行综合评述,讨论其未来发展和应用前景。     

Novel Umami Ingredients: Umami Peptides and Their Taste

Umami substances are very important for food seasoning and healthy eating. In addition to monosodium glutamate and some nucleotides, recent investigations have revealed that several peptides also exhibit umami taste. In recent years, 52 peptides have been reported to show umami taste, including 24 dipeptides, 16 tripeptides, 5 octapeptides, 2 pentapeptides, 2 hexapeptides, 1 tetrapeptide, 1 heptapeptide, and 1 undecapeptide. Twenty of these peptides have been examined for the present of umami taste. In this review, we have listed these umami peptides based on their category, source, taste, and threshold concentration. The evidence for peptides showing umami taste, the umami taste receptors on the human tongue, and the peptides whose umami taste is controversial are also discussed.     

Molecular Basis of Taste Sense: Involvement of GPCR Receptors

Taste perception is one of the senses crucial for many organisms. There are five basic tastes, i.e., sweet, bitter, salty, sour, and umami, and it is suggested that the taste of fat should be included in this list. This paper reviews the current state of knowledge about the involvement of G protein coupled receptors (GPCRs) in taste sensing and intracellular signaling. GPCR receptors are focal point of interest for pharmaceutical industry. However, their ability to interact with a variety of taste substances makes these receptors interesting target for food and nutrient companies.     

谷朊粉发酵液中鲜味肽的分离、鉴定与呈味分析

鲜味是五种基本味感之一,它在人们选择食品中扮演了越来越重要的角色,肽是氨基酸组成的混合物,具有多种味道,是主要的呈味物质,利用蛋白酶解可以获得具有较强鲜味的肽段。本实验采用感官评价结合超滤(UF)、凝胶层析(GPC)和反相高效液相色谱(RP-HPLC)等技术从以盐酸脱酰胺面筋蛋白为原料的发酵液中分离纯化得到一种鲜味肽,同时采用MALDI-TOF-MS串联质谱鉴定该鲜味肽的氨基酸序列及其分子质量;目标定向固相合成鉴别出的鲜味肽,并测定了其鲜味阈值及鲜味相乘效应。结果发现:该鲜味肽的氨基酸序列为Asp-Cys-Gly(DCG),分子质量为293.15 Da,固相合成该鲜味肽后采用滋味稀释法评价发现该鲜味肽的鲜味阈值为100 mg/m L,是MSG阈值的1/3,该鲜味肽对浓度为200 mg/L的I+G溶液具有鲜味增强作用,对MSG没有鲜味增强作用。     

Taste transduction: Linkage between molecular mechanisms and psychophysics

Taste transduction is initiated when taste stimuli interact with receptor sites on the exposed apical microvilli of receptor cells. The interaction leads to an increase in intracellular Ca⁺⁺ and transmitter release from the taste cell. Recent studies have revealed that taste cells utilize a diversity of mechanisms for transduction. Ionic taste stimuli, such as salts and acids, interact directly with apically located ion channels to depolarize taste cells. In contrast, amino acids, sweeteners and most bitter tasting stimuli bind to specific membrane receptors that are usually coupled to G proteins and second messenger systems. This review summarizes recent progress in understanding the initial events in taste transduction. Commonalities of molecular mechanisms for different taste stimuli may help explain psychophysical interactions of taste stimuli.     

基于模糊感官评价的黄羽肉鸡品种对鸡汤品质影响分析

以14 个不同品种的黄羽肉鸡为原料制作鸡汤,记录不同品种鸡的日龄、胴体质量和产地信息,测定鸡汤总游离氨基酸、总蛋白、肌苷酸、鸟苷酸、腺苷酸、天冬氨酸及谷氨酸含量等理化指标,并基于模糊感官评价方法分析不同品种鸡煮制鸡汤的感官品质。结果表明：鸡汤的等鲜浓度（equivalent umami concentration,EUC）与感官总评分具有极显著正相关性（P＜0.01）,与滋味评分具有显著正相关性（P＜0.05）,14 个肉鸡品种中固始老母鸡鸡汤滋味平均分最高,芦花鸡鸡汤综合感官品质最佳,且具有滋味鲜香、香味浓郁的特点。综上可知,在研究的品种中鲜味氨基酸和鲜味核苷酸含量较高的芦花鸡更适合煮制鸡汤。     

味觉感知的人体肠-脑轴信号传导机制研究进展

味觉是人类感知生物摄取能的重要环节,胃肠道亦存在味觉感知现象。本文从胃肠道味觉受体、胃肠道味觉感知通路及肠-脑轴味觉信号传导机制等方面进行了分析,胃肠道中味觉感知表明胃肠道中存在味觉受体第一家族亚型（taste receptor type 1 member,T1R）1、T1R2、T1R3、味觉受体第二家族亚型（taste receptors type 2,T2Rs）等味觉受体,且肠道味觉物质刺激肠内分泌细胞分泌胆囊收缩素（cholecystokinin,CCK）、肽YY（peptide YY,PYY）等脑肠肽激素,与味觉信号在神经元的传递有关;肠道中鲜味物质谷氨酸钠显著激活大脑缰核、杏仁核和下丘脑亚核的神经网络,表明肠-脑轴味觉感知是基于胃肠道受体及脑肠肽、神经元和大脑中枢神经系统之间的共同调控,从而提出肠-脑轴味觉信号传导机制假说,认为甜味受体T1R2/T1R3和鲜味受体T1R1/T1R3具有相似的信号传导通路,味觉物质作用于肠道后,与肠道中相应的味觉受体结合,激活磷脂酶-β2（phospholipase C-β2,PLC-β2）,释放Ca2＋,引起肠道内环境的变化,刺激肠内分泌细胞分泌PYY、CCK等激素,被肠神经元突触特异性识别,将味觉信号传导至大脑神经中枢;而谷氨酸代谢型受体4（metabotropic glutamate receptor 4,mGluR4）和苦味受体T2Rs信号传导通路则是通过激活磷酸二酯酶（phosphodiesterase,PDE）,使细胞质内3’,5’-环腺苷酸（3’,5’-cyclic adenylic acid,cAMP）浓度降低,从而解除环核苷酸（cyclic nucleotide,cNMP）的抑制作用,从而释放Ca2＋。基于肠-脑轴味觉偏好,为味觉发生改变的患者开发治疗新药物、寻找新的药物靶点提供了新的方向。对肠-脑轴味觉信号传导机制的研究将为胃肠道生理的神经控制提供分子框架、精准控制人体对味觉营养物质的生理反应,并对味觉物质在肠-脑轴中的摄入、代谢、调节等及开发新的味觉感知途径提供新的理论依据。     

Soy Sauce and Its Umami Taste: A Link from the Past to Current Situation

ABSTRACT: Soy sauce taste has become a focus of umami taste research. Umami taste is a 5th basic taste, which is associated to a palatable and pleasurable taste of food. Soy sauce has been used as an umami seasoning since the ancient time in Asia. The complex fermentation process occurred to soy beans, as the raw material in the soy sauce production, gives a distinct delicious taste. The recent investigation on Japanese and Indonesian soy sauces revealed that this taste is primarily due to umami components which have molecular weights lower than 500 Da. Free amino acids are the low molecular compounds that have an important role to the taste, in the presence of sodium salt. The intense umami taste found in the soy sauces may also be a result from the interaction between umami components and other tastants. Small peptides are also present, but have very low, almost undetected umami taste intensities investigated in their fractions.     

食品中呈鲜味物质研究进展

鲜味作为五大基本味之一,对于食品整体味道及人们对食品的评价至关重要。本文以鲜味为中心,从宏观角度介绍了富含鲜味的几种食物及影响其鲜味呈现的因素,总结了较新的几种鲜味提取方法,从微观角度综述了富含鲜味的几种氨基酸、核苷酸、肽、有机酸以及有机碱。简述了两种基本的鲜味受体蛋白——味型代谢性谷氨酸受体和味觉受体异源二聚体,并从鲜味感知和鲜味的协同增效作用两方面重点分析了鲜味的呈味机理。总结了当前常用的鲜味测定分析方法:感官评价法、高效液相色谱法、毛细管电泳法,以及比较新颖的生物和化学传感器法,为今后食品中鲜味物质的挖掘、感知、检测等研究提供参考。     

Analysis of binary taste-taste interactions of MSG,lactic acid,and NaCl by temporal dominance of sensations

Temporal dominance of sensations (TDS) is a relatively novel sensory evaluation technique that measures the temporal evolution of sensory perception. The sensory properties of food or drink products have been described by TDS; however, basic sensory data on TDS are still lacking. We analyzed TDS data for solutions of three basic tastes (umami, salty, and sour) and their binary combinations. The duration of TDS for the main taste of each type of solution (monosodium glutamate [MSG] for umami, sodium chloride [NaCl] for saltiness, and lactic acid for sourness) increased in a concentration-dependent manner. In addition, the duration of the umami taste of MSG was longer than that of MSG/inosine 5′-monophosphate solution with an umami taste of equivalent intensity. The duration of NaCl saltiness was increased by coexistence with MSG and decreased by coexistence with lactic acid. On the other hand, the duration of the umami taste of MSG was suppressed by coexistence with NaCl but not lactic acid, while the duration of the sour taste of lactic acid was suppressed by MSG but not NaCl. These findings provide novel insight into the temporal sequence of basic taste perception during food consumption.     

味觉受体研究热点分析

味觉是重要的感知反应，基本的味觉包括甜、酸、苦、咸、鲜5 种。味觉受体是用于感知各种味觉的蛋白质。本文对味觉受体热点关键词、来源、研究手段、受体类型、研究人员等进行分析概述，为开展味觉受体相关研究提供参考。通过文献分析发现，苦味、甜味、酸味、鲜味、大鼠、人类、小鼠、细胞、表达、蛋白质、诱导、基因、信号、神经元和分子等是味觉受体研究的热点关键词，Proceedings of the National Academy of Sciences、Journal of Neuroscience、American Journal of Physiology-Regulatory, Integrative and Comparative Physiology和Journal of Comparative Neurology是味觉受体研究领域的重点期刊。鼠类味觉受体是大多数实验的研究对象，然而鼠类和人类的味觉受体之间仍然存在较大差异，为更准确地探索人类味觉受体，还需对人类本身的味觉受体进行深入的研究。目前对味觉受体的研究已经进入结构生物学和神经生物学水平，主要采用分子生物学实验和计算机模拟技术等手段对受体结构进行探索。研究人员已经解析了青鳉鱼T1R2/T1R3配体识别结构域、斑马鱼Otop1和鸡Otop3的结构以及各味觉受体的信号传导通路，但大多数受体的精确结构还未解析出，也难以区分不同特点的味觉神经刺激。采用蛋白质表达纯化、蛋白质结构解析和信号传导等技术获得G蛋白偶联受体（G protein coupled receptors，GPCRs）的单晶体并解析晶体结构以及阐明各受体间的相互作用机理是目前重点的研究方向。美国目前在味觉受体研究领域处于领先地位，Ryba N. J. P.、Hoon M. A.和Chandrashekar J.等科学家目前引领了该领域的研究方向。本文明确了味觉受体领域发展现状，预测了味觉受体领域发展趋势，可为科研人员提供研究方向和思路。     

Research progress in the screening and evaluation of umami peptides

Umami is an important element affecting food taste, and the development of umami peptides is a topic of interest in food-flavoring research. The existing technology used for traditional screening of umami peptides is time-consuming and labor-intensive, making it difficult to meet the requirements of high-throughput screening, which limits the rapid development of umami peptides. The difficulty in performing a standard measurement of umami intensity is another problem that restricts the development of umami peptides. The existing methods are not sensitive and specific, making it difficult to achieve a standard evaluation of umami taste. This review summarizes the umami receptors and umami peptides, focusing on the problems restricting the development of umami peptides, high-throughput screening, and establishment of evaluation standards. The rapid screening of umami peptides was realized based on molecular docking technology and a machine learning method, and the standard evaluation of umami could be realized with a bionic taste sensor. The progress of rapid screening and evaluation methods significantly promotes the study of umami peptides and increases its application in the seasoning industry.