人乳中氨基酸的含量及分析方法研究进展

人乳中含有丰富的氨基酸,其中赖氨酸、苏氨酸、亮氨酸、缬氨酸、异亮氨酸、苯丙氨酸、甲硫氨酸和组氨酸等必需氨基酸构成比例合理,牛磺酸和谷氨酸等条件必需氨基酸含量丰富,丙氨酸、丝氨酸、天冬氨酸和甘氨酸等非必需氨基酸含量也较为丰富;人乳中含有的氨基酸在维持婴儿生长发育、增强免疫力、肠道保护等方面发挥重要作用.本文综述了人乳中主要氨基酸的含量及分析方法,以期为婴儿食品的开发及母乳成分数据库的建立提供一定的依据.     

氨基酸的毛细管电泳检测研究新进展

氨基酸是生命有机体的重要组成部分,参与人体各项生理活动和新陈代谢,在人体中发挥着特殊的作用,是人体必不可少的营养成分之一。近年来,生命科学的研究与食品、药品和保健品的开发,以及麻醉药品、精神药品对兴奋性神经递质的影响的研究,促进了对存在于各种检验材料中的氨基酸的分析方法的研究,探索高灵敏度和高选择性的氨基酸分析检测方法引起了人们极大的兴趣,所以建立快速、准确的氨基酸的检测方法越来越重要。毛细管电泳(capillary electrophoresis,CE)是继高效液相色谱之后发展起来的一种新的分离和分析方法,具有分离效率高、分析速度快、样品及试剂用量少等特点,本文参考近几年的相关文献,对氨基酸进行毛细管电泳检测使用紫外检测器、荧光检测器、电化学检测器和质谱检测器的方法作一综述。     

Determination of d-serine and related neuroactive amino acids in human plasma by high-performance liquid chromatography with fluorimetric detection

A simple and versatile methodology using high-performance liquid chromatography (HPLC) with fluorimetric detection was developed to simultaneously determine d-serine along with other metabolically related neuroactive amino acids in the glutamatergic system: L-serine, L-glutamate, L-glutamine, and glycine. On-column sensitivity was in the lower picomole range. Of two chiral thiol reagents investigated, amino acid derivatives of o-phthaldialdehyde (OPA) in combination with N-isobutyryl-L-cysteine were found to have consistently higher responses than their corresponding N-tert-butyloxycarbonyl-L-cysteine derivatives. This methodology was applied to the quantitative detection of amino acids in human plasma and lays the foundation for further investigations of the role of neuroactive amino acids in the pathophysiology and treatment of neurological and psychiatric disorders.     

Amino acids and their roles in tumor immunotherapy of breast cancer

Breast cancer is the most commonly diagnosed cancer among women. The primary treatment options include surgery, radiotherapy, chemotherapy, targeted therapy and hormone therapy. The effectiveness of breast cancer therapy varies depending on the stage and aggressiveness of the cancer, as well as individual factors. Advances in early detection and improved treatments have significantly increased survival rates for breast cancer patients. Nevertheless, specific subtypes of breast cancer, particularly triple-negative breast cancer, still lack effective treatment strategies. Thus, novel and effective therapeutic targets for breast cancer need to be explored. As substrates of protein synthesis, amino acids are important sources of energy and nutrition, only secondly to glucose. The rich supply of amino acids enables the tumor to maintain its proliferative competence through participation in energy generation, nucleoside synthesis and maintenance of cellular redox balance. Amino acids also play an important role in immune-suppressive microenvironment formation. Thus, the biological effects of amino acids may change unexpectedly in tumor-specific or oncogene-dependent manners. In recent years, there has been significant progress in the study of amino acid metabolism, particularly in their potential application as therapeutic targets in breast cancer. In this review, we provide an update on amino acid metabolism and discuss the therapeutic implications of amino acids in breast cancer.     

Role of neuromediators in the functioning of the human microbiota: “Business talks” among microorganisms and the microbiota-host dialogue

Current concepts concerning the social behavior of microorganisms inhabiting the human gastrointestinal (GI) tract and their role in the formation of integrated supracellular structures and in intercellular communication in the host–microbiota system are reviewed. The analysis of the literature data and of the results obtained by the authors indicates an important role of neuromediators (biogenic amines, amino acids, peptides, and nitric oxide) in intra- and interspecies microbial communication, as well as in the microbiota–host dialogue. The role of this dialogue for human health, its effect on the human psyche and social behavior, and the possibility of construction of probiotic preparations with a target-oriented neurochemical effect are discussed.     

Aflatoxin Contamination Detected in Nutrient and Anti-Oxidant Rich Edible Stink Bug Stored in Recycled Grain Containers

Recently, there has been multi-agency promotion of entomophagy as an environmentally-friendly source of food for the ever increasing human population especially in the developing countries. However, food quality and safety concerns must first be addressed in this context. We addressed these concerns in the present study using the edible stink bug Encosternum delegorguei, which is widely consumed in southern Africa. We analysed for mycotoxins, and health beneficials including antioxidants, amino acids and essential fatty acids using liquid chromatography coupled to quadrupole time of flight mass spectrometry (LC-Qtof-MS) and coupled gas chromatography (GC)-MS. We also performed proximate analysis to determine nutritional components. We identified the human carcinogen mycotoxin (aflatoxin B₁) at low levels in edible stink bugs that were stored in traditonally woven wooden dung smeared baskets and gunny bags previously used to store cereals. However, it was absent in insects stored in clean zip lock bags. On the other hand, we identified 10 fatty acids, of which 7 are considered essential fatty acids for human nutrition and health; 4 flavonoids and 12 amino acids of which two are considered the most limiting amino acids in cereal based diets. The edible stink bug also contained high crude protein and fats but was a poor source of minerals, except for phosphorus which was found in relatively high levels. Our results show that the edible stink bug is a nutrient- and antioxidant-rich source of food and health benefits for human consumption. As such, use of better handling and storage methods can help eliminate contamination of the edible stink bug with the carcinogen aflatoxin and ensure its safety as human food.     

Multi-layered network structure of amino acid (AA) metabolism characterized by each essential AA-deficient condition

Summary. The concentrations of free amino acids in plasma change coordinately and their profiles show distinctive features in various physiological conditions; however, their behavior can not always be explained by the conventional flow-based metabolic pathway network. In this study, we have revealed the interrelatedness of the plasma amino acids and inferred their network structure with threshold-test analysis and multilevel-digraph analysis methods using the plasma samples of rats which are fed diet deficient in single essential amino acid. In the inferred network, we could draw some interesting interrelations between plasma amino acids as follows: 1) Lysine is located at the top control level and has effects on almost all of the other plasma amino acids. 2) Threonine plays a role in a hub in the network, which has direct links to the most number of other amino acids. 3) Threonine and methionine are interrelated to each other and form a loop structure.     

The role of amino acid transporters in inherited and acquired diseases

Amino acids are essential building blocks of all mammalian cells. In addition to their role in protein synthesis, amino acids play an important role as energy fuels, precursors for a variety of metabolites and as signalling molecules. Disorders associated with the malfunction of amino acid transporters reflect the variety of roles that they fulfil in human physiology. Mutations of brain amino acid transporters affect neuronal excitability. Mutations of renal and intestinal amino acid transporters affect whole-body homoeostasis, resulting in malabsorption and renal problems. Amino acid transporters that are integral parts of metabolic pathways reduce the function of these pathways. Finally, amino acid uptake is essential for cell growth, thereby explaining their role in tumour progression. The present review summarizes the involvement of amino acid transporters in these roles as illustrated by diseases resulting from transporter malfunction.     

Improving amino acid nutrition to prevent intrauterine growth restriction in mammals

Intrauterine growth restriction (IUGR) is one of the most common concerns in human obstetrics and domestic animal production. It is usually caused by placental insufficiency, which decreases fetal uptake of nutrients (especially amino acids) from the placenta. Amino acids are not only building blocks for protein but also key regulators of metabolic pathways in fetoplacental development. The enhanced demands of amino acids by the developing conceptus must be met via active transport systems across the placenta as normal pregnancy advances. Growing evidence indicates that IUGR is associated with a reduction in placental amino acid transport capacity and metabolic pathways within the embryonic/fetal development. The positive relationships between amino acid concentrations in circulating maternal blood and placental amino acid transport into fetus encourage designing new therapies to prevent or treat IUGR by enhancing amino acid availability in maternal diets or maternal circulation. Despite the positive effects of available dietary interventions, nutritional therapy for IUGR is still in its infancy. Based on understanding of the underlying mechanisms whereby amino acids promote fetal growth and of their dietary requirements by IUGR, supplementation with functional amino acids (e.g., arginine and glutamine) hold great promise for preventing fetal growth restriction and improving health and growth of IUGR offspring.     

Strategies for comprehensive analysis of amino acid biomarkers of oxidative stress

Summary. Despite the wide interest in using modified amino acids as putative biomarkers of oxidative stress, many issues remain as to their overall reliability for early detection and diagnosis of diseases. In contrast to conventional single biomarker studies, comprehensive analysis of biomarkers offers an unbiased strategy for global assessment of modified amino acid metabolism due to reactive oxygen and nitrogen species. This review examines recent analytical techniques amenable for analysis of modified amino acids in biological samples reported during 2003–2007. Particular attention is devoted to the need for validated methods applicable to high-throughput analysis of multiple amino acid biomarkers, as well as consideration of sample pretreatment protocols on artifact formation for improved clinical relevance.     

功能性氨基酸在水产甲壳类动物中的研究进展和应用前景

传统氨基酸根据其在体内合成能力, 一般分为必需氨基酸和非必需氨基酸。目前最新研究认为, 部分氨基酸除了合成蛋白质以外, 也能够合成一系列功能性物质, 并对动物营养代谢和免疫功能具有十分重要的调节作用, 为此提出功能性氨基酸这一概念。功能性氨基酸在甲壳类促生长、提高免疫和存活率等方面效果显著。近些年来, 甲壳类动物养殖病害严重, 对高效抗病功能性饲料需求较高。功能性氨基酸将在未来甲壳类配合饲料升级中扮演着重要的角色。文章总结功能性氨基酸在甲壳类蜕壳、抗应激、增强饲料诱食性及提高繁殖和幼体培育等方面的具体作用, 为相关功能性饲料技术开发提供参考。     

High-performance liquid chromatographic analysis of physiological amino acids in human brain tumors by pre-column derivatization with phenylisothiocyanate

A reversed-phase high-performance liquid chromatographic technique for the determination of free amino acids in five biopsies of human brain tumors (two meningiomas, one glioblastoma and two oligodendrogliomas) is described. The frozen tissues were homogenized, deproteinized with perchloric acid and neutralized with potassium hydroxide. Aliquots of the supernatant containing the physiological amino acids are used for pre-column derivatization with phenylisothiocyanate. The derivatized PTC-amino acids (phenylthiocarbamyl derivatives) are stable for a five day period if stored as a powder at −20°C in an inert atmosphere and they can be analyzed on a reversed-phase column (PicoTag) using a gradient of two eluents with absorption detection at a wavelength of 254 nm. Good resolution of several amino acids (>30) is achieved within ca. 60 min. For most amino acids this method is suitable for an accurate measurement over a wide range of physiological concentrations (50–400 pmol) starting from a very small amount of sample.     

Mutagenesis and chimeric genes define determinants in the beta subunits of human chorionic gonadotropin and lutropin for secretion and assembly

Chorionic gonadotropin (CG) and lutropin (LH) are members of a family of glycoprotein hormones that share a common alpha subunit but differ in their hormone-specific beta subunits. The glycoprotein hormone beta subunits share a high degree of amino acid homology that is most evident for the LH beta and CG beta subunits having greater than 80% sequence similarity. However, transfection studies have shown that human CG beta and alpha can be secreted as monomers and can combine efficiently to form dimer, whereas secretion and assembly of human LH beta is less efficient. To determine which specific regions of the LH beta and CG beta subunits are responsible for these differences, mutant and chimeric LH beta-CG beta genes were constructed and transfected into CHO cells. Expression of these subunits showed that both the hydrophobic carboxy-terminal seven amino acids and amino acids Trp8, Ile15, Met42, and Asp77 together inhibit the secretion of LH beta. The carboxy-terminal amino acids, along with Trp8, Ile15, Met42, and Thr58 are implicated in the delayed assembly of LH beta. These unique features of LH beta may also play an important role in pituitary intracellular events and may be responsible for the differential glycosylation and sorting of LH and FSH in gonadotrophs.     

Mutational analysis of conserved residues in HhaI DNA methyltransferase

HhaI DNA methyltransferase belongs to the C5-cytosine methyltransferase family, which is characterized by the presence of a set of highly conserved amino acids and motifs present in an invariant order. HhaI DNA methyltransferase has been subjected to a lot of biochemical and crystallographic studies. A number of issues, especially the role of the conserved amino acids in the methyltransferase activity, have not been addressed. Using sequence comparison and structural data, a structure-guided mutagenesis approach was undertaken, to assess the role of conserved amino acids in catalysis. Site-directed mutagenesis was performed on amino acids involved in cofactor S-adenosyl-L-methionine (AdoMet) binding (Phe18, Trp41, Asp60 and Leu100). Characterization of these mutants, by in vitro /in vivo restriction assays and DNA/AdoMet binding studies, indicated that most of the residues present in the AdoMet-binding pocket were not absolutely essential. This study implies plasticity in the recognition of cofactor by HhaI DNA methyltransferase.     

Superoxide dismutases and their impact upon human health

Superoxide dismutases (SOD), a group of metal-containing enzymes, have a vital anti-oxidant role in human health, conferred by their scavenging of one of the reactive oxygen species, superoxide anion. Three types of SODs are known in humans, with the most abundant being cytosolic SOD1, identified by its Cu, Zn-containing prosthetic group. The presence of these metals and the coordination to certain amino acids are essential for function. SODs are among the first line of defense in the detoxification of products resulting from oxidative stress. Here, we describe the importance of SOD function, and the need for coordination with other ROS-scavenging enzymes in this pathway of detoxification. The impact of metal-deficient diets (copper or zinc) or incorrect metal ion incorporation (copper chaperone for SOD) onto nascent SOD, are also examined. Finally, human pathologies associated with either SOD dysfunction or decreased activity are discussed with current progress on the development of novel therapies.     

Isolation and analysis of natural compounds from silkworm pupae and effect of its extracts on alcohol detoxification

Silkworm pupae have much potential and many applications as a natural medicine to promote human health. However, their chemical components have not been fully characterized or understood. HPLC analysis was conducted to determine the content ratio (%) of individual amino acids in total protein of the pupae. It showed that glutamic acid (18.3%), histidine (14.6%) and alanine (10.2%) are the most common amino acids in silkworm pupae. Fatty acid composition of silkworm pupae oil was revealed by high‐pressure liquid chromatography and gas chromatography – mass spectroscopy analyses. They contain a high ratio of essential fatty acids, [α‐linolenic acid (ω‐3 fatty acid]+ linoleic acid) (49.0%), and also contain non‐essential fatty acids, oleic acid (19.9%), palmitoleic acid (2.5%), palmitic acid (19.7%), stearic acid (8.6%), and eicosapentaenoic acid (EPA) (0.3%). In addition, they also contain antioxidants, quercetin diglucoside and nutritionally important riboflavin (vitamin B2). This study suggests that silkworm pupae are a nutritionally valuable food product and are applicable as cosmetic components with essential amino acids, essential fatty acids, antioxidants and vitamins. The animal experiment showed that alcohol dehydrogenase (ADH) activity was significantly higher in the liver of mice orally administered with 0.5 mg/mL of silkworm extract and alcohol than with commercial Dawn808? and alcohol, indicating that silkworm pupae extracts have alcohol detoxification activity.     

Improving the levels of essential amino acids and sulfur metabolites in plants

Plants represent the major source of food for humans, either directly or indirectly through their use as livestock feeds. Plant foods are not nutritionally balanced because they contain low proportions of a number of essential metabolites, such as vitamins and amino acids, which humans and a significant proportion of their livestock cannot produce on their own. Among the essential amino acids needed in human diets, Lys, Met, Thr and Trp are considered as the most important because they are present in only low levels in plant foods. In the present review, we discuss approaches to improve the levels of the essential amino acids Lys and Met, as well as of sulfur metabolites, in plants using metabolic engineering approaches. We also focus on specific examples for which a deeper understanding of the regulation of metabolic networks in plants is needed for tailor-made improvements of amino acid metabolism with minimal interference in plant growth and productivity.     

Amino acid transport in isolated rat hepatocytes

Summary Improvements in the collagenase perfusion techniques have made isolated rat hepatocytes a popular model in which to study hepatic function. Our knowledge of hepatic amino acid transport has been advanced as a result of this methodology. Translocation across the hepatocyte plasma membrane can, in some instances, represent the rate-limiting step in the overall metabolism of certain amino acids. Furthermore, regulation of amino acid uptake by hepatocytes appears to play a role in diabetes, and perhaps in malignant transformation. Comparisons between normal adult hepatocytes and several hepatoma cell lines show basic differences in amino acids transport. There are at least eight distinct systems in normal hepatocytes for transport of the amino acids. One of these, System A, transports the small neutral amino acids most efficiently and responds to a wide variety of hormones. Systems A and N exhibit enhanced uptake rates after the cells have been maintained in the absence of extracellular amino acids, a phenomenon termed adaptive control. Further studies using isolated hepatocytes will increase our basic understanding of membrane transport processes and their regulation.     

氨基酸保健品的现状及发展趋势

随着社会经济的发展、人们生活水平的提高,氨基酸的各种功效逐渐被人们所熟知,在人们生活中扮演着越来越重要的角色,原本作为医用的氨基酸开始以保健品的形式走入人们的日常生活中。简要阐述了开发氨基酸保健品的必要性及现状,初步探讨了氨基酸保健品进一步的发展趋势。     

Behavioral reactions of the clawed toad Xenopus laevis to L- and D-isomers of amino acids

Studies on the action of L- and D-isomers of amino acids upon motor activity in the clawed toad revealed that most effective among them are basic amino acids (all of them being essential) and hydrophobic amino acids (mainly essential ones). Positive correlation was found between the effectiveness of hydrophobic amino acids on the motor activity of animals and their effectiveness with respect to taste receptors. The data obtained indicate the role of the olfactory receptors in realization of the behavioural reactions of the clawed toads to amino acids.