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。     

Mitochondria: aerobic and anaerobic design--lessons from molluscs and fishes

The contributions of Peter Hochachka to the development of comparative and adaptational biochemistry are substantial. In particular, he and his academic offspring made major contributions to the understanding of the metabolism of molluscs and fishes. These two large taxonomic groups each have marine, freshwater and terrestrial/semiterrestrial representatives, and their mitochondrial metabolism has been shaped by these environmental conditions. In particular, the importance of amino acids and lipids as energy sources has interesting correlations with the environment and the osmotic strategy used. In marine molluscs, amino acids are important aerobic energy sources, and are used as osmolytes and participate in anaerobic metabolism. In marine elasmobranchs, amino acids and ketone bodies, but not lipids per se, are important energy sources in extrahepatic tissues. Marine and freshwater teleost fish by contrast use lipids as an extrahepatic energy source with minimal use of ketone bodies. Furthermore, ketone bodies are important in the metabolism of freshwater and terrestrial but not marine molluscs. The bases for these different metabolic plans may lie in the solute systems used by the different groups (e.g. amino acids in marine molluscs and urea in marine elasmobranchs). The various metabolic options used by fishes and molluscs indicate the plasticity of metabolic design in an environmental context.     

Single dietary amino acids control resting egg production and affect population growth of a key freshwater herbivore

The enormous success of the genus Daphnia in freshwater ecosystems is at least partially due to their cyclical parthenogenetic life cycle, in which asexual and sexual reproduction alternate periodically. This temporal change between reproductive strategies allows for (1) rapid population growth via subitaneously developing eggs when environmental conditions are appropriate and (2) the maintenance of genetic diversity via sexual reproduction and the production of resting eggs when environmental conditions deteriorate. We show here that dietary amino acids are involved in triggering the switch between reproductive modes in Daphnia pulex. Supplementation experiments demonstrate that specific dietary amino acids, in particular arginine and histidine, avert crowding-induced resting egg production, enhance subitaneous reproduction by increasing algal food quality and, as a combined effect of both processes, increase population growth rates. These findings suggest that the availability of single dietary amino acids potentially affects the seasonal dynamics and long-term persistence of Daphnia populations in the field, which may have consequences for the efficiency of carbon transfer and thus the trophic structure of freshwater food webs.     

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.     

SALARECON connects the Atlantic salmon genome to growth and feed efficiency

Atlantic salmon (Salmo salar) is the most valuable farmed fish globally and there is much interest in optimizing its genetics and rearing conditions for growth and feed efficiency. Marine feed ingredients must be replaced to meet global demand, with challenges for fish health and sustainability. Metabolic models can address this by connecting genomes to metabolism, which converts nutrients in the feed to energy and biomass, but such models are currently not available for major aquaculture species such as salmon. We present SALARECON, a model focusing on energy, amino acid, and nucleotide metabolism that links the Atlantic salmon genome to metabolic fluxes and growth. It performs well in standardized tests and captures expected metabolic (in)capabilities. We show that it can explain observed hypoxic growth in terms of metabolic fluxes and apply it to aquaculture by simulating growth with commercial feed ingredients. Predicted limiting amino acids and feed efficiencies agree with data, and the model suggests that marine feed efficiency can be achieved by supplementing a few amino acids to plant- and insect-based feeds. SALARECON is a high-quality model that makes it possible to simulate Atlantic salmon metabolism and growth. It can be used to explain Atlantic salmon physiology and address key challenges in aquaculture such as development of sustainable feeds.     

Dietary requirements of “nutritionally non-essential amino acids” by animals and humans

Amino acids are necessary for the survival, growth, development, reproduction and health of all organisms. They were traditionally classified as nutritionally essential or non-essential for mammals, birds and fish based on nitrogen balance or growth. It was assumed that all “non-essential amino acids (NEAA)” were synthesized sufficiently in the body to meet the needs for maximal growth and health. However, there has been no compelling experimental evidence to support this assumption over the past century. NEAA (e.g., glutamine, glutamate, proline, glycine and arginine) play important roles in regulating gene expression, cell signaling, antioxidative responses, neurotransmission, and immunity. Additionally, glutamate, glutamine and aspartate are major metabolic fuels for the small intestine to maintain its digestive function and protect its mucosal integrity. Therefore, based on new research findings, NEAA should be taken into consideration in revising the classical “ideal protein” concept and formulating balanced diets to improve protein accretion, food efficiency, and health in animals and humans.     

Close encounters with eddies: oceanographic features increase growth of larval reef fishes during their journey to the reef

Like most benthic marine organisms, coral reef fishes produce larvae that traverse open ocean waters before settling and metamorphosing into juveniles. Where larvae are transported and how they survive is a central question in marine and fisheries ecology. While there is increasing success in modelling potential larval trajectories, our knowledge of the physical and biological processes contributing to larval survivorship during dispersal remains relatively poor. Mesoscale eddies (MEs) are ubiquitous throughout the world''s oceans and their propagation is often accompanied by upwelling and increased productivity. Enhanced production suggests that eddies may serve as important habitat for the larval stages of marine organisms, yet there is a lack of empirical data on the growth rates of larvae associated with these eddies. During three cruises in the Straits of Florida, we sampled larval fishes inside and outside five cyclonic MEs. Otolith microstructure analysis revealed that four of five species of reef fish examined had consistently faster growth inside these eddies. Because increased larval growth often leads to higher survivorship, larvae that encounter MEs during transit are more likely to contribute to reef populations. Successful dispersal in oligotrophic waters may rely on larval encounter with such oceanographic features.     

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.     

Valeur trophique des acides aminés dans les graines de légumineuses et développement larvaire de Callosobruchus maculatus

Interspecific variation of protein amino acids between peanut, horse bean, french bean, lentil, cowpea and chick-pea was undertaken in relation to larval development of C. maculatus. Twenty-one groups of amino acids were identified and quantified. In all seeds, free amino acids exist in low quantities; but they are more numerous than bound amino acids. Essential amino acids for man are sufficient in the six species, except for the sulphur amino acids in all seeds, and for lysine in peanut. Utilization of those pulses, after cooking, in human food complements cereals. Larval development possibilities of C. maculatus upon the used seeds shows up that: (a) with chick-pea and cowpea, the bruchid thrives normally. However, although amino acids are higher in cowpea than in chick-pea, the better performances were observed on the latter; (b) peanut, french bean, horse bean and lentil are unsuitable for larval development of the insect. Although they are rich in amino acids, all larvae die at first in star within these pulses. We conclude that larval development of C. maculatus does not depend only on the amounts of amino acids in the seeds but also on other trophic factors. These could consist of the balance between different nutritive compounds and the presence of allelochemical substances in the tested seeds which bruchid larvae are unable to utilize.     

Metabolic organization of the spotted ratfish, Hydrolagus colliei (Holocephali: Chimaeriformes): insight into the evolution of energy metabolism in the chondrichthyan fishes

The metabolic organization of a holocephalan, the spotted ratfish (Hydrolagus colliei), was assessed using measurements of key enzymes of several metabolic pathways in four tissues and plasma concentrations of free amino acids (FAA) and non-esterified fatty acids (NEFA) to ascertain if the Holocephali differ metabolically from the Elasmobranchii since these groups diverged ca. 400 Mya. Activities of carnitine palmitoyl transferase indicate that fatty acid oxidation occurs in liver and kidney but not in heart or white muscle. This result mirrors the well-established absence of lipid oxidation in elasmobranch muscle, and more recent studies showing that elasmobranch kidney possesses a capacity for lipid oxidation. High activities in oxidative tissues of enzymes of ketone body metabolism, including D-beta-hydroxybutyrate dehydrogenase, indicate that, like elasmobranchs, ketone bodies are of central importance in spotted ratfish. Like many carnivorous fishes, enzyme activities demonstrate that amino acids are metabolically important, although the concentration of plasma FAA was relatively low. NEFA concentrations are lower than in teleosts, but higher than in most elasmobranchs and similar to that in some "primitive" ray-finned fishes. NEFA composition is comparable to other marine temperate fishes, including high levels of n-6 and especially n-3 polyunsaturated fatty acids. The metabolic organization of the spotted ratfish is similar to that of elasmobranchs: a reduced capacity for lipid oxidation in muscle, lower plasma NEFA levels, and an emphasis on ketone bodies as oxidative fuel. This metabolic strategy was likely present in the common chondrichthyan ancestor, and may be similar to the ancestral metabolic state of fishes.     

Storage of nutriments by adult female Glossina morsitans and their transfer to the intra-uterine larva

Administration of U-¹⁴C arginine, histidine, leucine, lysine, phenylalanine, threonine, tyrosine, or valine into the haemolymph of female Glossina morsitans on the first day of the pregnancy cycle was followed by radiometric analysis of the post-parturient larva. Radioactivity in the larva, expressed as a percentage of the administered activity, was low with histidine (0.3%) and arginine (2.3%) but higher with the other six amino acids (8.2% to 16.8%). ¹⁴C incorporation in the larval lipid was extremely low with arginine and histidine, but with the remaining six amino acids lipids showed the most ¹⁴C labelling. Radioactivity was detected in the larval amino acids corresponding to those injected into the female parents. Further radiometric study using labelled leucine showed that during the first 5 days of pregnancy surplus leucine was largely converted to lipids for larval growth. Thereafter, while the rate of leucine-derived ¹⁴C incorporation in the larval lipids declined rapidly that in the larval proteins increased. Implications are that female G. morsitans has a significant capacity to store nutriments derived from bloodmeals ingested during early pregnancy destined for larval development, and that normal growth of the intra-uterine progeny is a function of optimum feeding throughout the pregnancy cycle.     

Effects of larval starvation and adult diet-derived amino acids on reproduction in a fruit-feeding butterfly

Availability of adequate nutrition is among the most important factors affecting growth, development, and reproduction in animals. In holometabolous insects, diets and nutritional needs change between life stages, with larval storage, and adult feeding and reproduction being linked to one another. In several butterfly species, adult feeding is of fundamental importance to realize the full reproductive potential, primarily due to a prominent role of adult diet-derived carbohydrates. In contrast, the role of adult diet-derived amino acids is still under debate, despite the fact that butterflies were often found to preferentially feed on amino acid-rich substrates. Recently it was found that amino acids from adult income could compensate for adverse effects of larval food quality. In our study on the tropical butterfly Bicyclus anynana (Butler) (Lepidoptera: Nymphalidae), we used larval starvation to investigate corresponding effects on female reproductive output. Short periods of larval starvation prolonged development time and reduced larval survival, larval growth rate, pupal mass, and egg size. Regardless of the degree of larval starvation, access to amino acids in the adult diet increased egg size, whereas egg number remained largely unaffected. Thus, although there was some evidence for adult diet-derived amino acids being overall beneficial to reproduction, there was no indication that they can compensate for larval starvation.     

The physiology of digestion in fish larvae

Synopsis The acquisition, digestion, and assimilation of food is critical for the growth and survival of fish larvae; a fish larva either grows or it perishes. Fish larvae are characterized by digestive systems and diets that differ from adults. Larvae undergo a pattern of trophic ontogeny, changing diet with increasing size, and these changes result in differences in digestive requirements. At first feeding, the larval alimentary canal is functional, but is structurally and functionally less complex than that of adults. The larval alimentary canal remains unchanged histologically during the larval period before transformation. During transformation, major changes that result in the development of the adult alimentary canal occur. The ontogeny of the alimentary canal differs in different taxa, and experimental evidence suggests that functional differences exist as well. Assimilation efficiency may be lower in larvae than it is in adult fishes, due to a lack of a morphological and functional stomach in larvae, but the question of improving assimilation efficiencies during larval development before transformation remains unresolved.     

Ontogenetical aspects of nutritional requirements in fish

Changes in morphology i.e. "metamorphosis", mode of respiration, allometric growth of organs, mode of swimming and efficiency of biochemical pathways are briefly reviewed. It is suggested that these processes form the basis for progressive changes in nutrient requirements involving formation and development of several organs, systems and function. Digestive tract morphology changes during ontogenesis and aspects of fish metabolism, protein synthesis rate and body growth rate are interconnected and an attempt is made to explain these processes so as to understand the specificity of larval and juvenile fish nutrient requirements as compared to subadults. Protein and amino acid requirements given the body mass perspective and the generalization of the protein maintenance requirement in protein requirements for maximum growth was estimated to amount to 5-20%. Several cases of amino acid deficiency symptoms showed strong dependence on fish weight (age), but even most numerous studies on salmonids are lacking complete research throughout the life history of one species in defined nutritional and environmental conditions. Larval and juvenile fish have reduced capacity of catabolic adaptability and this fact links them to strictly carnivorous mammals. An attempt is made, for the first time, to relate amino acid needs of fish to young and/or carnivorous mammals. Vitamin requirements of fish are reviewed, taking into account the relationship between body size and time of the first appearance of deficiency symptoms. These are virtually no studies on vitamin requirements in larval warm-water fishes and very few on first feeding salmonids. The same applies to the vitamin need in reproductory fish. Fatty acid deficiencies manifest themselves faster in juvenile fish, but larval fish might require separate classes of lipids, phosphatidylcholine, in the diet to develop and grow at all. It seems that the studies on nutrient requirements have so far not used an ontogenetical perspective, but evidence given throughout this work argues that it would be worthwhile.     

Amino acid uptake profiling of wild type and recombinant Streptomyces lividans TK24 batch fermentations

Streptomyces lividans is considered an interesting host for the secretory production of heterologous proteins. To obtain a good secretion yield of heterologous proteins, the availability of suitable nitrogen sources in the medium is required. Often, undefined mixtures of amino acids are used to improve protein yields. However, the understanding of amino acid utilization as well as their contribution to the heterologous protein synthesis is poor.In this paper, amino acid utilization by wild type and recombinant S. lividans TK24 growing on a minimal medium supplemented with casamino acids is profiled by intensive analysis of the exometabolome (metabolic footprint) as a function of time. Dynamics of biomass, substrates, by-products and heterologous protein are characterized, analyzed and compared. As an exemplary protein mouse Tumor Necrosis Factor Alpha (mTNF-α) is considered.Results unveil preferential glutamate and aspartate assimilation, together with glucose and ammonium, but the associated high biomass growth rate is unfavorable for protein production. Excretion of organic acids as well as alanine is observed. Pyruvate and alanine overflow point at an imbalance between carbon and nitrogen catabolism and biosynthetic fluxes. Lactate secretion is probably related to clump formation. Heterologous protein production induces a slowdown in growth, denser clump formation and a shift in metabolism, as reflected in the altered substrate requirements and overflow pattern. Besides glutamate and aspartate, most amino acids are catabolized, however, their exact contribution in heterologous protein production could not be seized from macroscopic quantities.The metabolic footprints presented in this paper provide a first insight into the impact and relevance of amino acids on biomass growth and protein production. Type and availability of substrates together with biomass growth rate and morphology affect the protein secretion efficiency and should be optimally controlled, e.g., by appropriate medium formulation and substrate dosing. Overflow metabolism as well as high biomass growth rates must be avoided because they reduce protein yields. Further investigation of the intracellular metabolic fluxes should be conducted to fully unravel and identify ways to relieve the metabolic burden of plasmid maintenance and heterologous protein production and to prevent overflow.     

A versatile enrichment of functionalized calixarene as a facile sensor for amino acids

Amino acids are the most important part of the human biological system due to their role in living processes. The role of amino acids stretches beyond their traditional role as a building block for proteins, and deficiency of amino acids could lead to decreased immunity, digestive problems, depression, fertility issues, lower mental alertness, slowed growth in children, and many other health issues. The acute detection of amino acids is necessary to determine the human health domain. Here, in this review, we summarize and study the calixarenes as complexes that are of immeasurable value and their utilization for amino acid detection. Key factors such as noncovalent forces, limit of detection, and the supramolecular chemistry of calixarenes with amino acids have been well described. This study presents the most recent efforts made towards the development of potential and highly efficient calixarene-based sensors for the detection of amino acids.     

Amino acids: metabolism,functions, and nutrition

Recent years have witnessed the discovery that amino acids (AA) are not only cell signaling molecules but are also regulators of gene expression and the protein phosphorylation cascade. Additionally, AA are key precursors for syntheses of hormones and low-molecular weight nitrogenous substances with each having enormous biological importance. Physiological concentrations of AA and their metabolites (e.g., nitric oxide, polyamines, glutathione, taurine, thyroid hormones, and serotonin) are required for the functions. However, elevated levels of AA and their products (e.g., ammonia, homocysteine, and asymmetric dimethylarginine) are pathogenic factors for neurological disorders, oxidative stress, and cardiovascular disease. Thus, an optimal balance among AA in the diet and circulation is crucial for whole body homeostasis. There is growing recognition that besides their role as building blocks of proteins and polypeptides, some AA regulate key metabolic pathways that are necessary for maintenance, growth, reproduction, and immunity. They are called functional AA, which include arginine, cysteine, glutamine, leucine, proline, and tryptophan. Dietary supplementation with one or a mixture of these AA may be beneficial for (1) ameliorating health problems at various stages of the life cycle (e.g., fetal growth restriction, neonatal morbidity and mortality, weaning-associated intestinal dysfunction and wasting syndrome, obesity, diabetes, cardiovascular disease, the metabolic syndrome, and infertility); (2) optimizing efficiency of metabolic transformations to enhance muscle growth, milk production, egg and meat quality and athletic performance, while preventing excess fat deposition and reducing adiposity. Thus, AA have important functions in both nutrition and health.     

Synergistic effects of metabolically related amino acids on the growth of a multicellular plant

The effects of several amino acids related to the metabolism of aspartic acid on the growth and development of gemmalings of the liverwort Marchantia polymorpha were investigated under axenic conditions. Lysine and theonine synergistically inhibit the growth of these plants and cause a loss of normal pigmentation at concentrations as low as 1 μm. These effects are highly specific for this pair of amino acids, are partially reversible upon removal of the effectors, and can be prevented by low concentrations of methionine or its metabolic precursor, homoserine. Alterations in the growth and development of gemmalings in the presence of natural amino acids are discussed in relation to metabolic regulatory mechanisms which have been well established in microorganisms.