乳源性生物活性肽及其生物学与保健意义

乳中含有大量的生物活性肽,或自然存在于乳中,或来自乳的酶解产物。前一类生物活性肽包括表皮生长因子(EGF) 、转化生长因子(TGF) 、神经生长因子(NGF) 、胰岛素及胰岛素样生长因子Ⅰ和Ⅱ(IGF—Ⅰ、IGF—Ⅱ) 。初乳中这类生物活性肽的浓度一般高于血液中的浓度。由于初生动物胃肠道的蛋白酶活性低以及乳中存在蛋白酶抑制因子,这些活性肽能在哺乳期动物的消化道内存活。饲喂EGF、胰岛素和IGF—Ⅰ可加快新生动物胃肠道的发育,因此其对调节哺乳期幼仔胃肠道发育有重大作用。后一类生物活性肽包括酪啡肽、免疫调节肽、血管紧张素Ⅰ转化酶(ACE) 抑制肽,这些活性肽构成了乳蛋白的主要结构,并可经酶水解而释放出来,在乳消化过程中这些肽可能是潜在的生理调节因子。     

生物活性肽

生物活性肽是对生物机体的生命活动有益或具有生理作用的肽类化合物,简述了生物活性肽的分类、特点、作用机理以及开发应用。     

海藻肽的化学结构特征和活性作用研究进展

海藻中的肽类化合物具有显著的生物活性和药理作用,对其氨基酸序列及活性作用的研究已经取得了一些重要进展。发现的海藻肽类化合物并确定其化学结构式的主要有二肽、环肽和脂肽,这些肽类化合物具有抗肿瘤、降血压、降血脂、抗凝血、促进神经细胞分化、抗氧化、抗菌和抗病毒等生物活性。预测海藻肽类化合物在疑难病症的治疗上将发挥重要作用。     

酶法制备海洋活性肽及其功能活性研究进展

海洋生物活性肽(Marine biological active peptide)是从海洋生物中提取的具有优化机体代谢环境、有益于机体健康的一类多肽。酶法制备海洋生物活性肽是目前最常用的制备方法,是通过适当的蛋白酶水解海洋生物蛋白来制备生物活性肽的一种方法。海洋生物活性肽在降血压、抗氧化、抗凝血及抗菌等方面效果显著,对治疗和预防疾病具有巨大潜力。介绍海洋生物活性肽在酶解制备及其生物学功能方面国内外研究进展,为进一步开展海洋活性多肽研究提供参考。     

生物活性肽自动查询预测系统

论述了运用生物信息学方法和计算机技术,快速从由蛋白酶模拟酶解蛋白质而产生的大量未知生物活性的系列肽中,预测有生物活性的肽,以实现生物活性肽功能的预测。主要建立了生物活性肽数据库,应用已有生物活性肽作为序列比对的标准,实行大量未知生物活性的系列肽自动无人值守的和已知生物活性的肽序列比对查询,以发现新物种中包括动物和植物的具有新的生物活性的功能肽。应用该软件系统AQS成功地预测并发现了造血细胞增殖肽、成骨细胞生长肽以及高血压押制肽。     

乳酪蛋白源生物活性肽的研究进展

酪蛋白是生物活性肽的重要来源,可以通过体内的胃肠消化和食品加工过程中的酶解将其释放出来。乳酪蛋白源的生物活性肽的生物学意义、对人类健康的影响和其在新型功能性食品加工中的作用具有重要的研究价值。     

生物活性低聚肽生理功能的研究进展

相比多肽，低聚肽具有优异的吸收机制与生物活性，本文主要从生物活性低聚肽生理功能的角度综述生物活性低聚肽的研究进展，并对生物活性低聚肽的研究前景进行了展望。     

淡水鱼生物活性肽及其生物活性研究进展

淡水鱼生物活性肽是以淡水鱼为原料,采用酶解等方法从淡水鱼蛋白质中得到的具有独特理化特性和生物学活性的小肽物质。目前,从淡水鱼中已分离出多种具有生物活性的肽段,但关于淡水鱼源肽的结构和活性之间关系的报道尚不多。本文综述了淡水鱼生物活性肽的种类、制备与纯化和应用前景,并对未来进行了展望,以期为淡水鱼活性肽的进一步研究和开发利用提供参考。     

食源性生物活性肽免疫调节功能的研究

生物活性肽通常用来表示生物进行生命活动过程中起到调控作用的化学物质,它在机体内发挥了一系列作用。肽由相应的蛋白质所组成,在化学上通过电解能够获取蛋白水解物质,对免疫系统具有极大的调节作用。最近,因为其制备的原材料易于获取且其效用都非常显著,科学家们纷纷将调查研究的目光锁定其中。本研究对食源性生物活性肽的吸收机制、常见种类、制备方法以及研究现状进行了综述,并对其发展前景进行了展望。     

乳清蛋白及其生物活性肽血压调节功能研究进展

乳清蛋白既是优质蛋白来源，也是抗高血压生物活性肽的理想来源，开发具有调节血压功效的蛋白多肽类产品对未来临床高血压防治将发挥重要作用。文章综述了乳清蛋白生物活性肽血压调节功能的基本机制和研究现状，并对其未来发展趋势和应用前景进行了讨论。     

In vivo digestomics of milk proteins in human milk and infant formula using a suckling rat pup model

Human milk is the optimal mode of infant feeding for the first several months of life, and infant formulas serve as an alternative when breast-feeding is not possible. Milk proteins have a balanced amino acid composition and some of them provide beneficial bioactivities in their intact forms. They also encrypt a variety of bioactive peptides, possibly contributing to infant health and growth. However, there is limited knowledge of how milk proteins are digested in the gastrointestinal tract and bioactive peptides are released in infants. A peptidomic analysis was conducted to identify peptides released from milk proteins in human milk and infant formula, using a suckling rat pup model. Among the major milk proteins targeted, α-lactalbumin and β-casein in human milk, and β-lactoglobulin and β-casein in infant formula were the main sources of peptides, and these peptides covered large parts of the parental proteins’ sequences. Release of peptides was concentrated to specific regions, such as residues 70–92 of β-casein in human milk, residues 39–55 of β-lactoglobulin in infant formula, and residues 57–96 and 145–161 of β-CN in infant formula, where resistance to gastrointestinal digestion was suggested. In the context of bioactive peptides, release of fragments containing known bioactive peptides was confirmed, such as β-CN-derived opioid and antihypertensive peptides. It is therefore likely that these fragments are of biological significance in neonatal health and development.     

Bioactive peptides derived from human milk proteins — mechanisms of action

Human milk contains a multitude of bioactive proteins with very diverse functions, which are beneficial for the rapidly growing neonate. The large variety of bioactivities is accomplished by the combination of bioactive proteins per se and gastrointestinal release of bioactive peptides derived from them. The bioactivities exerted by these peptides include enhancement of mineral absorption, immunomodulation, opioid, antihypertensive and antimicrobial activities. Notably, several of the activities are not attributed to the parental proteins, but exclusively to released bioactive peptides. This article reviews studies on bioactive peptides derived from major human milk proteins, such as caseins, α-lactalbumin and lactoferrin, during gastrointestinal digestion. Studies of bovine milk counterparts are also cited as a comparison.     

Identification of the human beta-casein C-terminal fragments that specifically bind to purified antibodies to bovine beta-lactoglobulin

The presence of foreign proteins in human milk after the ingestion of bovine dairy products is thought to be one of the possible causes of allergic sensitization in exclusively breast-fed predisposed infants. The immunologic determination of bovine beta-lactoglobulin (LG) concentration in human milk has been reported by several researchers, but the results are conflicting. Moreover, a strong cross-reactivity between antibodies to bovine beta-LG and human milk proteins and peptides was reported, throwing doubt on the reliability of radioimmunoassay and enzyme-linked immunosorbent assay detection and quantification assays for bovine beta-LG in human milk. Thus, the goal of this study was to isolate human milk peptides with a molecular mass >or= 1,000 Da cross-reactive with antibodies to bovine beta-LG in order to identify possible common epitopes between human and bovine milk proteins. The proteins were first isolated by affinity chromatography with purified polyclonal antibodies to bovine beta-LG, followed by gel filtration fast phase liquid chromatography and reverse phase-high performance liquid chromatography purification of the components specifically bound in the affinity separation step. Affinity-bound peptides were identified by determining their amino acid sequence. All the sequenced peptides belonged to the C-terminal part of human beta-casein, which confirms the cross-reactivity of human milk proteins and peptides with antibodies to bovine beta-LG and allows the identification of possible common epitopes between the two proteins. No bovine beta-LG peptides with a molecular mass >or= 1,000 Da were found in our milk samples from healthy mothers on a diet rich in bovine milk and dairy products.     

Multifunctional peptides encrypted in milk proteins

Many bioactivities of milk are latent in that they are inactive within the protein sequence, requiring enzymatic proteolysis for release of bioactive peptides from milk proteins precursors. Bioactivities of peptides encrypted in major milk proteins are latent until released and activated, e.g. during gastrointestinal digestion or food processing. Bioactive peptides can be produced in vivo following intake of milk proteins, and the proteolytic system of bacterial species used in the production of fermented milk products and cheese can contribute to the liberation of bioactive peptides or precursors thereof. Activated peptides are potential modulators of various regulatory processes in the living system: immunomodulatory peptides stimulate the activities of cells of the immune system and several cytomodulatory peptides inhibit cancer cell growth, antimicrobial peptides kill sensitive microorganisms, angiotensin-I-converting enzyme (ACE)-inhibitory peptides exert an hypotensive effect, opioid peptides are opioid receptor ligands which can modulate absorption processes in the intestinal tract, mineral binding peptides may function as carriers for different minerals, especially calcium. Many milk-derived peptides reveal multifunctional properties, i.e. specific peptide sequences having two or more different biological activities have been reported. Milk protein-derived bioactive peptides are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.     

Peptidome analysis of human skim milk in term and preterm milk

The abundant proteins in human milk have been well characterized and are known to provide nutritional, protective, and developmental advantages to both term and preterm infants. Due to the difficulties associated with detection technology of the peptides, the expression of the peptides present in human milk is not known widely. In recent years, peptidome analysis has received increasing attention. In this report, the analysis of endogenous peptides in human milk was done by mass spectrometry. A method was also developed by our researchers, which can be used in the extraction of peptide from human milk. Analysis of the extracts by LC–MS/MS resulted in the detection of 1000–3000 Da peptide-like features. Out of these, 419 peptides were identified by MS/MS. The identified peptides were found to originate from 34 proteins, of which several have been reported. Analysis of the peptides’ cleavage sites showed that the peptides are cleaved with regulations. This may reflect the protease activity and distribution in human body, and also represent the biological state of the tissue and provide a fresh source for biomarker discovery. Isotope dimethyl labeling analysis was also used to test the effects of premature delivery on milk protein composition in this study. Differences in peptides expression between breast milk in term milk (38–41 weeks gestation) and preterm milk (28–32 weeks gestation) were investigated in this study. 41 Peptides in these two groups were found expressed differently. 23 Peptides were present at higher levels in preterm milk, and 18 were present at higher levels in term milk.     

Characterization of new milk-derived inhibitors of angiotensin converting enzyme in vitro and in vivo

Inhibition of angiotensin converting enzyme (ACE) has been observed with a variety of different peptides, and peptide fragments with inhibitory capabilities have been identified within many different proteins, including milk proteins. The purpose of this study therefore was to identify new short peptides with inhibitory properties from the primary structure of milk proteins and to characterize them in vitro and in vivo, since no milk derived ACE inhibitors have previously been evaluated for their ability to inhibit ACE in vivo. In vitro, 8 of 9 dipeptides were found to be competitive inhibitors of ACE. The IC50 was significantly lower when an angiotensin I-like substrate was used, than when a bradykinin-like substrate was used. Using three different in vivo models for ACE inhibition, a very moderate effect was observed for three of the new peptides, but only for up to 6 or 12 minutes. Nothing was observed with two reference compounds that are reported to be hypotensive ACE-inhibitors derived from milk proteins. This raises the question whether the mechanism of hypotensive action is straightforward inhibition of ACE in vivo.     

In silico identification of novel ACE and DPP-IV inhibitory peptides derived from buffalo milk proteins and evaluation of their inhibitory mechanisms

The capacity of buffalo milk proteins to release bioactive peptides was evaluated and novel bioactive peptides were identified. The sequential similarity between buffalo milk proteins and their cow counterparts was analysed. Buffalo milk proteins were simulated to yield theoretical peptides via in silico proteolysis. The potential of selected proteins to release specific bioactive peptides was evaluated by the A value obtained from the BIOPEP–UWM database (Minkiewicz et al. in Int J Mol Sci 20(23):5978, 2019). Buffalo milk protein is a suitable precursor to produce bioactive peptides, particularly dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibitory peptides. Two novel ACE inhibitory peptides (KPW and RGP) and four potential DPP-IV inhibitory peptides (RGP, KPW, FPK and KFTW) derived from in silico proteolysis of buffalo milk proteins were screened using different integrated bioinformatic approaches (PeptideRanker, Innovagen, peptide-cutter and molecular docking). The Lineweaver–Burk plots showed that KPW (IC₅₀?=?136.28?±?10.77 μM) and RGP (104.72?±?8.37 μM) acted as a competitive inhibitor against ACE. Similarly, KFTW (IC₅₀?=?873.92?±?32.89 μM) was also a competitive inhibitor of DPP-IV, while KPW and FPK (82.52?±?10.37 and 126.57?±?8.45 μM, respectively) were mixed-type inhibitors. It should be emphasized that this study does not involve any clinical trial.

     

Characterization of New Milk-derived Inhibitors of Angiotensin Converting Enzyme In Vitro and In Vivo

Inhibition of angiotensin converting enzyme (ACE) has been observed with a variety of different peptides, and peptide fragments with inhibitory capabilities have been identified within many different proteins, including milk proteins. The purpose of this study therefore was to identify new short peptides with inhibitory properties from the primary structure of milk proteins and to characterize them in vitro and in vivo, since no milk derived ACE inhibitors have previously been evaluated for their ability to inhibit ACE in vivo. In vitro, 8 of 9 dipeptides were found to be competitive inhibitors of ACE. The IC₅₀ was significantly lower when an angiotensin I-like substrate was used, than when a bradykinin-like substrate was used. Using three different in vivo models for ACE inhibition, a very moderate effect was observed for three of the new peptides, but only for up to 6 or 12 minutes. Nothing was observed with two reference compounds that are reported to be hypotensive ACE-inhibitors derived from milk proteins. This raises the question whether the mechanism of hypotensive action is straightforward inhibition of ACE in vivo.     

Human milk provides peptides highly stimulating the growth of bifidobacteria.

The large intestine of breast-fed infants is colonized predominantly by bifidobacteria, which have a protective effect against acute diarrhea. In this study we report for the first time the identification of human milk peptides that selectively stimulate the growth of bifidobacteria. Several bifidogenic peptides were purified chromatographically from pepsin-treated human milk and identified as proteolytically generated fragments from the secretory component of the soluble polyimmunoglobulin receptor and lactoferrin; both of these proteins exhibit antimicrobial effects. Hydrolysis of the identified peptides with the gastrointestinal proteases pepsin, trypsin and chymotrypsin did not lead to the loss of bifidogenic activity, indicating their potential function in vivo. Sequential comparison revealed a similar structural motif within the identified peptides. A correspondingly designed small peptide (prebiotic lactoferrin-derived peptide-I, PRELP-I) was found to stimulate the growth of bifidobacteria as effectively as the native peptides. The combination of antimicrobial and bifidobacterial growth stimulatory activity in human milk proteins leads to highly specific compounds capable of regulating the microbial composition of infants' large intestine.     

Nutritional,antimicrobial and medicinal properties of Camel’s milk: A review

Camel’s milk is an important part of staple diet in several parts of the world, particularly in the arid and semi-arid zones. Camel’s milk is rich in health-beneficial substances, such as bioactive peptides, lactoferrin, zinc, and mono and polyunsaturated fatty acids. These substances could help in the treatment of some important human diseases like tuberculosis, asthma, gastrointestinal diseases, and jaundice. Camel’s milk composition is more variable compared to cow’s milk. The effects of feed, breed, age, and lactation stage on milk composition are more significant in camel. Region and season significantly change the ratio of compounds in camel’s milk. Camel’s whey protein is not only composed of numerous soluble proteins, but also has indigenous proteases such as chymotrypsin A and cathepsin D. In addition to their high nutritional value, these whey proteins have unique characteristics, including physical, chemical, physiological, functional, and technological features that are useful in the food application. The hydrolysis of camel’s milk proteins leads to the formation of bioactive peptides, which affect major organ systems of the body and impart physiological functions to these systems. The camel’s milk has antioxidant, antimicrobial, angiotensin-I-converting enzyme (ACE)-inhibitory peptides, antidiabetic as well as anticholesterol activities.