Some features of the regulation of the free amino acids in adult Calliphora erythrocephala

The amounts of nearly every amino acid in Calliphora remain unchanged inspite of stress. Thus the free amino acid pool is regulated. The amounts of free amino acid in the haemolymph account for only a small part of the total free amino acid in a fly and therefore most free amino acid is located and regulated intracellularly. A comparison of the rates of conversion and turnover of glycine-C¹⁴ in flies fed protein and sugar and in flies fed sugar alone indicates that in the absence of a dietary source of amino acid, not only is the rate of total turnover appreciably lower but the rates of conversion to other amino acids also change. With a dietary source of amino acid, the rates of incorporation into protein account for only a part of the total turnover of each amino acid. With a sufficiency of amino acid, substantial amounts are probably used as an energy source.     

Infusion of amino acids decreases the hyperglycaemic effect of per- and postoperative glucose infusion: an experimental study in the rabbit

The effects on blood glucose concentration of 10% glucose with amino acid solution at low (18%) and high (25%) concentration of branched chain amino acids were studied, two days after laparotomy in fasted rabbits. During the whole study period, saline infusion was associated with normoglycaemia. Among the other infusion combinations peroperative infusion of amino acid solution high in branched chain amino acids with 10% glucose was the least hyperglycaemic. An amino acid solution low in branched chain amino acids with 10% glucose had the lowest hyperglycaemic effect 24 hours postoperatively. After 48 hours an infusion of 10% glucose produced the weakest hyperglycaemia. In preoperatively and 24 hours postoperatively 10% glucose was more hyperglycaemic than 10% glucose with the two amino acid solutions. After 24 and 48 hours, infusion of 10% glucose with amino acids high in branched chain amino acids was more hyperglycaemic than 10% glucose with amino acids low in branched chain amino acids.     

On the antisymmetry of the amino acid code table

Antisymmetry of the amino acid code table in terms of codon degeneracy is pointed out, and it is related to a physico-chemical problem of codon-anticodon interaction energy. A strong negative correlation between molecular weight of an amino acid and its codon degeneracy is pointed out, and its implication to the origin of the amino acid code table is discussed. Finally, an earlier form of the amino acid code table is proposed.     

Accq.Tag法测定氨基酸口服液的氨基酸含量

采用AccQ .Tag法对氨基酸口服液中游离氨基酸和牛磺酸含量进行了分离测定。产品中氨基酸总量达 85mg/ml以上 ,共 1 3种氨基酸。必需氨基酸与非必需氨基酸比例为 2 .2 0～ 2 .50∶1 ,支 /芳比为 2 .30～ 2 .55∶1 .配方接近于FAO氨基酸比例模式 ,以FAO氨基酸模式及化学评分评价了该制剂的营养价值 ,基本上不存在限制氨基酸 ,化学评分均在 90分以上。     

橄榄蚶软体部营养成分分析与评价

测定了橄榄蚶(EsteUarca olivacea)软体部的基本生化成分、氨基酸和脂肪酸的含量.结果表明,橄榄蚶软体部含水量为81.36%,粗蛋白、粗脂肪、总糖和灰分分别占软体部干重的63.64%、10.95%、13.55%和8.97%.橄榄蚶软体部含有18种氨基酸,总氨基酸、必需氨基酸和呈味氨基酸分别占软体部干重的54.83%、19.80%和27.54%,总氨基酸占软体部蛋白质的86.13%,必需氨基酸和呈味氨基酸分别占氨基酸总量的36.11%和56.52%.橄榄蚶的限制性氨基酸为蛋氨酸+胱氨酸和色氨酸.橄榄蚶软体部含28种脂肪酸,不饱和脂肪酸(UFA)、单不饱和脂肪酸(MUFA)、多不饱和脂肪酸(PuFA)及"w-3系列多不饱和脂肪酸(w-3PUFA)分别占脂肪酸的41.31%、23.06%、18.25%和10.54%,DHA和EPA分别占脂肪酸的2.82%和4.59%.     

Differential effects of amino acids on the period of the circadian rhythm from the Aplysia eye

The effect of continuous treatments of single L -amino acids (0.1mM) on the free running rhythm from the isolated Aplysia eye was examined. A variation in the change in free running period produced by different amino acids was observed. Two well-known precursors of neurotransmitter (tyrosine, tryptophan) had the largest effects. These amino acids lengthened the period ca. 1.7 h. Another group of amino acids (alanine, threonine, proline) lengthened the period by about 1 h. Smaller effects were produced by aspartic acid and leucine and no effects were caused by lysine, glycine, valine, and serine. Phenylalanine may shorten the period a small amount. Glucose (5mM) lengthens the period a small amount (0.4 h), decreases the effect of tyrosine somewhat, and has no effect on the lengthening of the period produced by tryptophan. Three amino acids not involved in protein synthesis (ornithine, β-alanine, citrulline) had at most small effects on the free running period. Also, D -tryptophan lengthened the period by 0.6 h but the effect of D -tryptophan was considerably smaller than the effect of L -tryptophan. A few of the amino acids had small short-term effects on spike rate and longer-term effects on the amplitudes of the rhythms but these effects did not correlate with the effects of the amino acids on the free running period. Though continuous treatments of certain amino acids lengthened the periods, shorter treatments (tryptophan, 6 h) did not phase-shift the rhythm. Since eyes maintained in a commonly used culture medium have longer periods than eyes in a simple seawater medium, the amino acids of the culture medium must be responsible, at least in part, for the lengthening effect of the culture medium. The mechanism of action of the amino acids is unknown. The magnitude of the effects did not correlate with physical-chemical properties of the amino acids nor with whether the amino acids were “essential” or “nonessential.” The effects of the amino acids may be mediated by their effects on neurotransmitter and/or protein synthesis.     

Optimizing the protein nutrition of growing-finishing pigs

Growing-finishing pigs should consume each day the minimum amounts of energy and amino acids needed for maximum lean deposition. This should optimize performance traits, carcass leanness, and N excretion. These ideal conditions are difficult to achieve under experimental or farm conditions due to the factors affecting amino acid requirements and feed intake on a daily basis. Lean deposition rate and sex are two of the major factors affecting amino acid needs. If possible, maximum lean deposition rates should be determined for each herd in order to customize feeding programs, and split-sex feeding will improve N utilization.

Amino acid requirements have been determined empirically and by the factorial method. The latter is preferred if the efficiency of use of absorbed amino acids can be accurately determined. Development of computer models will likely be needed to accomplish this. Apparent ileal digestibility of amino acids is the most practical means of estimating amino acid absorption at present, although it likely overestimates amino acid availability for some amino acids.

Crystalline amino acids can be used to improve amino acid balance and reduce excessive intake of protein which should improve feed efficiency. A portion of the high-quality protein feeds in pig diets can be replaced by synthetic amino acids without sacrificing performance, but the effects of these substitutions on carcass merit is uncertain.

Excretion of N, and the concomitant reduction of N in manure that has to be disposed of, can be manipulated nutritionally by increased use of crystalline amino acids to lower dietary protein, by use of highly digestible feedstuffs and by precise matching of amino acid needs to amino acid supply. Use of these factors could lead to a reduction in total N wastes of 20–30%.     

炒焦对山楂中氨基酸含量的影响分析

为探索炒焦对山楂中氨基酸的影响及山楂炒焦过程中氨基酸的变化,对炒焦前后山楂中氨基酸含量的变化进行了分析.测定结果显示,炒焦前后山楂中氨基酸的种类不变,各种氨基酸含量变化不一;方差分析显示炒焦前后氨基酸的含量变化不显著,炒焦对山楂中氨基酸的影响较小.由于山楂在炒焦过程具备发生美拉德反应的物质基础和客观条件,推测山楂中的氨...     

An Analysis of the Metabolic Theory of the Origin of the Genetic Code

A computer program was used to test Wong's coevolution theory of the genetic code. The codon correlations between the codons of biosynthetically related amino acids in the universal genetic code and in randomly generated genetic codes were compared. It was determined that many codon correlations are also present within random genetic codes and that among the random codes there are always several which have many more correlations than that found in the universal code. Although the number of correlations depends on the choice of biosynthetically related amino acids, the probability of choosing a random genetic code with the same or greater number of codon correlations as the universal genetic code was found to vary from 0.1% to 34% (with respect to a fairly complete listing of related amino acids). Thus, Wong's theory that the genetic code arose by coevolution with the biosynthetic pathways of amino acids, based on codon correlations between biosynthetically related amino acids, is statistical in nature. Received: 8 August 1996 / Accepted: 26 December 1996     

Utilization of amino acids during development of the African migratory locust embryo

Summary The metabolic fate of amino acids introduced into the locust egg by the addition of amino acids after oviposition is compared to that of amino acids derived from the maternal haemocoel. It was found that amino acids from the two sources did not always follow the same pattern of utilization. Topical application resulted in some of the applied amino acids being converted into other amino acids and ammonia. When the labelled amino acid was administered to the egg via the maternal haemocoel, radioactivity was restricted to the amino acid orginally provided.     

鱼腥草种质资源氨基酸组成及含量分析

分别对鱼腥草16个不同居群幼嫩地上和地下部分的氨基酸成分进行高效液相色谱分析。结果发现,鱼腥草不同居群的氨基酸含量不尽相同,同一居群幼嫩地上茎叶和地下茎的氨基酸含量也有差异,多以地上茎叶高于地下茎。在分析的17种氨基酸中,所有居群均含有16种氨基酸,都不含Cys-SS-Cys。地上部分氨基酸中Glu含量最高,His含量最低;地下部分氨基酸中Glu含量最高,Tyr含量最低。地上部分氨基酸总量以W01-16为最高,而地下部分氨基酸总量以W01-99为最高,分别为27.89mg/g和15.46mg/g。蕺菜与峨眉蕺菜间氨基酸成分间无显著差别。鱼腥草种质资源氨基酸含量与染色体数目间相关不显著。     

诺丽果与热带水果中氨基酸含量及组成对比分析

以诺丽果和16种海南常见热带水果为材料,对比分析了氨基酸含量及组成。结果表明:诺丽果含有18种氨基酸,种类齐全。其氨基酸总量、人体必需氨基酸含量和儿童必需氨基酸含量均居第1位。诺丽果的E/T值为37.13%,E/N值为0.59,符合理想蛋白质的要求。诺丽果中各种人体必需氨基酸,Val、Ile、Leu、Phe+Tyr、M et+Cys、Thr的含量占氨基酸总量的比例,与1973年FAO/WHO修订的人体必需氨基酸含量模式谱基本一致,仅Lys中度缺乏。诺丽果中鲜味类、芳香族、甜味类氨基酸含量居第1位。     

Impact of the C-N status on the amino acid profile in tobacco source leaves

This paper investigates the influence of the carbon (C) and nitrogen (N) status on the amino acid profile in tobacco source leaves. Treatments used included growing plants at different light intensities, using an antisense RBCS (small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase) construct to inhibit Rubisco activity, growing plants on 12 or 0.5 mM nitrate, comparing wild-types with genotypes that have small and large decreases in nitrate reductase (NIA) activity, and sampling plants at different times during the diurnal cycle. This combination of experiments provides information on how amino acid levels respond to several inputs including the C and N status, nitrate, excess light and light-dark transitions. The data set was analysed using principal component analysis, regression analysis and by normalizing the level of each individual amino acid on the total amino acid pool. Most amino acids show a downward trend when the C or the N status is decreased, and rise during day and fall at night during the diurnal cycle. However, individual amino acids often showed deviating responses. Furthermore, no evidence was found for feedback inhibition of minor amino acid synthesis, either within or between pathways, when 18 individual amino acids were supplied to detached leaves. Results indicate that regulation of amino acid metabolism, for example by the C and N status, leads to qualitatively similar responses of many amino acids, but homeostatic mechanisms involving feedback inhibition within or between individual amino acid biosynthesis pathways are not stringent. All of the above inputs affect the level of phenylalanine, an amino acid that is also the substrate for an important sector of secondary metabolism. The levels of glutamate were remarkably constant, indicating that unknown mechanisms stabilize the concentration of this key central amino acid. Analyses of metabolite levels and feeding experiments indicated that 2-oxoglutarate plays an important role in regulating glutamate levels. Glutamate was the most effective inhibitor of NIA activity when 18 individual amino acids were supplied to detached leaves. Feeding glutamate, and other downstream amino acids, led to an increase of glutamine, indicating glutamate exerts feedback regulation on ammonium metabolism.     

Submerged culture conidial germination and conidiation of the bioherbicideColletotrichum truncatum are influenced by the amino acid composition of the medium

Summary Submerged culture experiments were conducted to determine the optimal nitrogen source for rapidly producing conidia of the bioherbicide,Colletotrichum truncatum. Germination ofC. truncatum conidial inocula in submerged culture occurred most rapidly (>95% in 6 h) in media provided with a complete complement of amino acids. When (NH₄)₂SO₄, urea, or individual amino acids were provided as the sole nitrogen source, conidial germination was less than 20% after 6 h incubation. Conidia production was delayed inC. truncatum cultures grown in media with urea or individual amino acids as nitrogen sources compared to cultures supplied with Casamino acids or complete synthetic amino acid nitrogen sources. The use of methionine, lysine, tryptophan, isoleucine, leucine or cysteine as a sole nitrogen source severely inhibitedC. truncatum conidia production. Media with synthetic amino acid mixtures less these inhibitory amino acids produced significantly higher conidia yields compared to media with amino acid mixtures containing these amino acids. When various amounts of each individual inhibitory amino acid were added to media which contained amino acid mixtures, cysteine and methionine were shown to be most effective in reducing conidiation. An optimal nitrogen source forC. truncatum conidiation in submerged culture should contain a complete mixture of amino acids with low levels of cysteine, methionine, leucine, isoleucine, lysine and tryptophan for rapid conidiation and optimal conidia yield.The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.     

The atmosphere of the primitive Earth and the prebiotic synthesis of amino acids

The atmosphere of the Earth at the time of its formation is now generally believed to have been reducing, an idea proposed by Oparin and extensively discussed by Urey. This atmosphere would have contained CH₄, N₂ with traces of NH₃, water and hydrogen. Only traces of NH₃ would have been present because of its solubility in water. UV light and electric discharges were the major sources of energy for amino acid synthesis, with electric discharges being the most efficient, although most other sources of energy also give amino acids.The first prebiotic electric discharge synthesis of amino acids showed that surprisingly high yields of amino acids were synthesized. Eleven amino acids were identified, four of which occur in proteins. Hydroxy acids, simple aliphatic acids and urea were also identified. These experiments have been repeated recently, and 33 amino acids were identified, ten of which occur in proteins, including all of the hydrophobic amino acids.Methionine can be synthesized by electric discharges if H₂S or CH₃SH is added to the reduced gases. The prebiotic synthesis of phenylalanine, tyrosine and trytophan involves pyrolysis reactions combined with plausible solution reactions.Eighteen amino acids have been identified in the Murchison meteorite, a type II carbonaceous chondrite, of which six occur in proteins. All of the amino acids found in the Murchison meteorite have been found among the electric discharge products. Furthermore, the ratios of amino acids in the meteorite show a close correspondence to the ratios from the electric discharge synthesis, indicating that the amino acids on the parent body of the carbonaceous chondrites were synthesized by electric discharges or by an analogous process.     

Influence of the yeast strain on the changes of the amino acids,peptides and proteins during sparkling wine production by the traditional method

The influence of five yeast strains on the nitrogen fractions, amino acids, peptides and proteins, during 12 months of aging of sparkling wines produced by the traditional or Champenoise method, was studied. High-performance liquid chromatography (HPLC) techniques were used for analysis of the amino acid and peptide fractions. Proteins plus polypeptides were determined by the colorimetric Bradford method. Four main stages were detected in the aging of wines with yeast. In the first stage, a second fermentation took place; amino acids and proteins plus polypeptides diminished, and peptides were liberated. In the second stage, there was a release of amino acids and proteins, and peptides were degraded. In the third stage, the release of proteins and peptides predominated. In the fourth stage, the amino acid concentration diminished. The yeast strain used influenced the content of free amino acids and peptides and the aging time in all the nitrogen fractions. Received 25 March 2002/ Accepted in revised form 31 July 2002     

Expansion of the Genetic Code Through the Use of Modified Bacterial Ribosomes

Biological protein synthesis is mediated by the ribosome, and employs ~20 proteinogenic amino acids as building blocks. Through the use of misacylated tRNAs, presently accessible by any of several strategies, it is now possible to employ in vitro and in vivo protein biosynthesis to elaborate proteins containing a much larger variety of amino acid building blocks. However, the incorporation of this broader variety of amino acids is limited to those species utilized by the ribosome. As a consequence, virtually all of the substrates utilized over time have been L-α-amino acids. In recent years, a variety of structural and biochemical studies have provided important insights into those regions of the 23S ribosomal RNA that are involved in peptide bond formation. Subsequent experiments, involving the randomization of key regions of 23S rRNA required for peptide bond formation, have afforded libraries of E. coli harboring plasmids with the rrnB gene modified in the key regions. Selections based on the use of modified puromycin derivatives with altered amino acids then identified clones uniquely sensitive to individual puromycin derivatives. These clones often recognized misacylated tRNAs containing altered amino acids similar to those in the modified puromycins, and incorporated the amino acid analogues into proteins. In this fashion, it has been possible to realize the synthesis of proteins containing D-amino acids, β-amino acids, phosphorylated amino acids, as well as long chain and cyclic amino acids in which the nucleophilic amino group is not in the α-position. Of special interest have been dipeptides and dipeptidomimetics of diverse utility.     

海洋生物保健制剂中氨基酸的测定及营养评价

本文对以海参、鱼翅、鱼鳔等为主要原料,添加一些具有食疗作用的中药而制成具有不同功效的６种保健制剂,测定了其中的游离氨基酸及１８种常见氨基酸的含量。以ＦＡＯ／ＷＨＯ的氨基酸模式及化学评分,评价了这些保健制剂的蛋白质营养价值。限制性氨基酸主要是赖氨酸和（或）亮氨酸。这些制剂的氨基酸评分大多数都很高,有４种制剂的化学评分在９０分以上。     

Control of amino acid transport in the mammary gland of the pregnant mouse

The regulation of the uptake of the amino acid analog α-aminoisobutyric acid was studied in diced mammary glands from pregnant mice. Stimulation of uptake by insulin was not prevented by inhibitors of protein synthesis; protein synthesis inhibitors decreased uptake by 20%; this response occurred more promptly in insulintreated tissues. Elimination of extracellular amino acids led to a substantial increase in transport which was not abolished by inhibitors of protein synthesis. These results indicate that insulin does not increase amino acid transport in this system by altering synthesis and degradation of transport protein. They are consistent with a model in which the activity of the existing amino acid transport protein is subject to negative feedback regulation from the intracellular amino acid pool.     

On the origin of the genetic code

It is argued that three chemical criteria determined the evolution of the genetic code: codon-anticodon pairing; codon-amino acid pairing; amino acid pairing. The first criterium determined the set of interactive nucleotides; the second, the set of nucleotides interactive with amino acids; the third, the set of mutually interactive amino acids. The code resulted from the intersection of these sets. This hypothesis explains the specificity and universality of the code as well as the “choice” of the standard amino acids and nucleotides from among those available in nature. The specific mechanism for codon-amino acid pairing assumed here is the “backwards” (Crick, 1967) Pelc-Welton (1966) models. Three types of evidence support “backwards” pairing: parallel genetic coding of amino acid pairs (Root-Bernstein, 1982); results of binding experiments by Saxinger and Ponnamperuma (1974); reinterpretation of Jungck's (1978) correlations between the properties of amino acids and their respective anticodon nucleotides. The inversion of the code to its present state occurred as a result of the evolution of tRNA molecules which supplanted parallel codon-amino acid interactions with antiparallel codon-anticodon ones. The paper concludes with suggestions for testing the hypothesis.