Impact of potassium,sodium, and salinity on the protein-and free amino acid content of wheat grain

A lysimeter study was conducted on Cajeme wheat (Triticum aestivum L.) to investigate the impact of salinity on protein and free amino acid content of the grain. Cross correlations were obtained between 16 different soil-plant-water based parameters and the concentration and total accumulation of amino acids. The results indicated that after 3 years of irrigation, the majority of protein bound and free amino acids increased in concentration in the grain. However, both free tryptophan and free proline revealed decreasing concentrations with increasing salinity. Free tryptophan showed a synergism between total accumulation, yield and concentration. Free proline concentrations decreased in association with increasing protein concentrations. Cross correlations of the 16 soil-plant-water based parameters with free and protein bound amino acids revealed significant correlations for free aspartic acid and glycine with total accumulation but not with concentrations. Only methionine plus cystine was lower than suggested FAO levels for essential amino acids and was lower in the third year than in the first year.     

Seasonal patterns of nucleic acid concentrations and amino acid profiles of Parapenaeus longirostris (Crustacea, Decapoda): relation to growth and nutritional condition

The present work describes the seasonal changes in nucleic acid concentrations and amino acid profiles in the muscle of juvenile Parapenaeus longirostris and their relation to growth and nutritional condition. RNA content varied significantly between seasons, being the highest values attained in spring and the lowest in winter (p < 0.05). Similar results were obtained with RNA:protein and RNA:DNA ratios. In respect to total amino acid content (TAA), a significant increase from winter to spring was observed (p < 0.05) and the major essential amino acids (EAA) were arginine, histidine and leucine. Within non-essential amino acids (NEAA) glutamic acid, aspartic acid, glycine and proline were dominant. From winter to spring, a significant variation in NEAA content occurred (26.8; p < 0.05), mainly due to the significant increase of glutamic acid (79.1) and serine (66.7) (p < 0.05). EAA content did not vary significantly between seasons (p > 0.05). In opposition, during this period a significant decrease in the free amino acid content (FAA) was observed (p < 0.05); a higher percentage of decrease was attained in free non-essential (FNEAA – 42.9) in comparison to free essential amino acids (FEAA – 40.2). The significant increase in RNA and TAA contents from winter to spring may be related with protein synthesis. On the other hand, the lowest values obtained in winter may be due to a reduction in feeding activity; in this period the muscle protein must be progressively hydrolysed, which is evident with the higher FAA content. The liberated amino acids enter FAA pool and become available for energy production. In conclusion, it was evident that the seasonal cycle in activities such as feeding and growth with nucleic acids and amino acid analyses was noticed.     

Amino Acid Metabolism of Lemna minor L. : I. Responses to Methionine Sulfoximine

When Lemna minor L. is supplied with the potent inhibitor of glutamine synthetase, methionine sulfoximine, rapid changes in free amino acid levels occur. Glutamine, glutamate, asparagine, aspartate, alanine, and serine levels decline concomitantly with ammonia accumulation. However, not all free amino acid pools deplete in response to this inhibitor. Several free amino acids including proline, valine, leucine, isoleucine, threonine, lysine, phenylalanine, tyrosine, histidine, and methionine exhibit severalfold accumulations within 24 hours of methionine sulfoximine treatment. To investigate whether these latter amino acid accumulations result from de novo synthesis via a methionine sulfoximine insensitive pathway of ammonia assimilation (e.g. glutamate dehydrogenase) or from protein turnover, fronds of Lemna minor were prelabeled with [¹⁵N]H₄⁺ prior to supplying the inhibitor. Analyses of the ¹⁵N abundance of free amino acids suggest that protein turnover is the major source of these methionine sulfoximine induced amino acid accumulations. Thus, the pools of valine, leucine, isoleucine, proline, and threonine accumulated in response to the inhibitor in the presence of [¹⁵N]H₄⁺, are ¹⁴N enriched and are not apparently derived from ¹⁵N-labeled precursors. To account for the selective accumulation of amino acids, such as valine, leucine, isoleucine, proline, and threonine, it is necessary to envisage that these free amino acids are relatively poorly catabolized in vivo. The amino acids which deplete in response to methionine sulfoximine (i.e. glutamate, glutamine, alanine, aspartate, asparagine, and serine) are all presumably rapidly catabolized to ammonia, either in the photorespiratory pathway or by alternative routes.     

Quantitative analysis of free amino acids and carbohydrates in spring barley anthers at different stages of maturity

The content of the carbohydrates glucose, fructose and sucrose was determined in spring barley anthers at different stages of maturity. During maturation the sucrose content of the anthers increased markedly. The following 17 free amino acids were detected in anthers of different stages of maturity: aspartic acid, glutamic acid, serine, alanine, arginine, leucine, isoleucine, lysine, α-aminobutyric acid, glutamine, proline, tyrosine, phenylalanine, valine, threonine, cystine and glycine. Quantitative analysis was only carried out in amino acids present in higher concentrations in the analysed samples. These were: aspartic acid, glutamic acid, α-aminobutyric acid, proline, serine, valine and glutamine, and a mixture of amino acids (leucine, isoleucine, valine and phenylalanine). The total content of free amino acids increased with increasing maturity of the anthers. However, not all amino acids followed contributed to this increase, but only proline, glutamic acid, aspartic acid and glutamine. A small difference was found in the variety Gopal in which the aspartic acid content did not increase significantly, but the content of the mixture of amino acids and serine did. With the exception of green anthers of the variety Firlbecks Union, proline was present in the highest concentration in all samples analysed.     

Biochemical factors affecting protein accumulation in the rice grain

Rice grains (Oryza sativa L.) from three varieties and three pairs of lines with different protein content were collected at 4-day intervals from 4 to 32 days after flowering. The samples were analyzed for protein, free amino nitrogen, ribonucleic acid, protease activity, and ribonuclease activity. In addition, the capacity of the intact grain to incorporate amino acids was determined for the three pairs of lines. The maximal level of free amino nitrogen and the capacity of the developing grain to incorporate amino acids were consistently found to be higher in the samples with the high protein content in the mature grain. The ribonucleic acid content of the grain tended to be higher in the high protein samples.     

Aspects of amino acid metabolism and nutrition in the ectoparasitoid wasp, Exeristes roborator

Exeristes roborator contains a wide variety of free amino acids, and the composition of all developmental stages was quantitatively dominated by proline and glutamic acid. The latter occurred together with lesser amounts of glycine, alanine, valine, leucine, tyrosine, and histidine which varied between developmental stages. Minor and trace amounts of most other commonly occurring amino acids were also found. The percentages or relative amounts of major constituents were not influenced when the parasite was reared on the alternate hosts, Pectinophora gossypiella and Gnorimoschema operculella. Likewise, the major characteristics of the latter hosts' free amino compositions could not be accounted for, in either case, by their diets.Differences in the relative distribution of the major amino acids between the developmental stages of E. roborator indicate large decreases in the percentage of proline occur during development from the larval to the adult stage with corresponding increases in the percentages of glycine in the pupal stage and alanine as well as other amino acids in the adult stage. The results suggest that proline may play an important rôle in E. roborator, probably as an energy reserve.The amino acid compositions of the total proteins of E. roborator and its hosts were similar and all quantitatively dominated by glutamic acid, aspartic acid, and amides. However, the disk gel electropherograms of the proteins of both hosts and parasite were different. Quantitative changes were evident in the protein pattern of the parasite when reared on the alternate hosts.E. roborator incorporated radioactivity from ¹⁴C(U)-glucose into the amino acids, glutamic acid, aspartic acid, serine, glycine, alanine, and proline. Furthermore, ¹⁴C(U)-glutamic acid was incorporated into a wide variety of proteins. The data suggest that the above amino acids may be non-essential dietary components for E. roborator. However, quantitative determinations indicate that the amount of glutamic acid synthesized does not account for the amount incorporated into protein over the same time period.     

外源一氧化氮、水杨酸和过氧化氢对烟草叶片游离氨基酸和可溶性蛋白含量的影响

测定了NO、SA和H2O2三种信号分子对烟草氮代谢产物游离氨基酸、脯氨酸和可溶性蛋白质含量的影响。结果表明：NO、SA和H2O2能调节烟草脯氨酸、游离氨基酸和可溶性蛋白质含量。低浓度的NO和H2O2处理后12h能提高脯氨酸含量,而较高浓度的NO、SA和H2O2处理降低烟草脯氨酸和游离氨基酸含量;三者对脯氨酸、游离氨基酸和可溶性蛋白质含量的影响具有相似性。     

Amino Acid Composition of Bulk Protein of Euglena Grown in Waste Water

The amino acid content of bulk protein in a sewage-grown Euglena sp. was examined. Concentrations of the essential amino acids, threonine, histidine, tryptophan, and valine, were similar to those found in other algae. The concentration of alanine was much higher. Methionine was not found at all, proline only in traces, and other amino acids at low concentrations. These results indicate that the amino acid content of bulk protein of the species of Euglena studied resembles that of plants far more closely than that of animals.     

Measurement of total protein in plant samples in the presence of tannins

A method for measuring total protein in situ in plant samples has been developed using the determination of amino acids released by acid hydrolysis of dried plant material. Standard proteins and plant samples were hydrolyzed with 3% sulfuric acid at 100 degrees C for 24 h and the amino acids released were measured with ninhydrin. Unhydrolyzed plant extracts were also analyzed for free amino acids with ninhydrin. Total amino acid equivalents (protein plus free amino acids) of a diverse set of plant samples was significantly correlated with total protein as estimated by elemental analysis (N X 6.25). The Lowry method as modified by precipitation of proteins with trichloroacetic acid was found to be unsatisfactory for dried plant samples due to the incomplete extractability of proteins. Although some alkaloids caused increased absorbance with ninhydrin, interference with quantification of protein is likely to be minimal. Tannins interfered with the Lowry and Bradford methods but not the ninhydrin method.     

Salivary amino acids in Lygus species (Heteroptera:Miridae)

Free and protein-bound amino acids were investigated in the phytophagous bug Lygus rugulipennis and its salivary gland. Over 38 substances were separated. The total content of amino compounds in the insects was about 1400 μmol/g fr. wt (16% by weight), of which 97% was amino acid residues in proteins.The salivary glands, which comprise about 1.5% of the live weight of the insects, contain 3.5% of the total free amino acids and 1% of the whote insect. Free and protein-bound amino acids comprise, respectively, about 1.4 and 11.6% of the fresh weight of the gland. The total concentration of free amino acids in the saliva was estimated to range from 0.5 to 2.2% by weight (ca. 0.1 M).The composition of free amino acids in the salivary gland of Lugus varies markedly. In four studied species (L. rugulipennis, L. gemellatus, L. pratensis, L. punctatus), the most abundant compounds were proline, arginine, lysine, leucine, glutamic acid, methionine sulphoxide and glycerophosphoethanolamine. In whole specimens of L. rugulipennis the predominant free amino acids were proline, alanine, taurine, glutamic acid, glutamine and methionine sulphoxide. The most abundant amino acids in proteins were glutamic and aspartic acid, glycine, alanine and leucine. The results indicate that the amino acid composition in the salivary glands of Lygus species does not differ markedly from that of the whole insect. The functions of salivary amino acids are discussed.     

Biochemical Changes in Terminal Root Galls Caused by an Ectoparasitic Nematode,Longidorus africanus: Amino Acids

The amino acids of terminal root galls caused by Longidorus africanus on bur marigold (Bidens tripartita L.) and grapevine (Vitis vinifera L.) were studied. The galled roots of bur marigold contained 73% more cell-wall protein and 184% more free amino acids. The main changes among the free amino acids of the galled tissue were a large increase (1900%) in proline and a decrease in aspartic acid (56%) compared with the respective check tissue. Hydroxyproline decreased in the wall protein fraction from 5.6% in the healthy tissue to 3.6% in the infected tissue.Percent of hydroxyproline in total amino acids of the wall protein fraction of grapevine roots decreased from 0.7% in the healthy tissue to 0.3% in the galled tissue, and total proteins of this fraction decreased from 9.5 mg to 4.5 rag, respectively. Total protein in the protoplasmic fraction also decreased from 3.0 mg in healthy to 1.0 mg in infected roots. No change was noticed in total proteins in the free amino acids fraction but free proline decreased 40% in the infected roots.The relationship of these differences to the specific reactions of the hosts to nematode feeding is discussed.     

Metabolism of Proline, Glutamate, and Ornithine in Proline Mutant Root Tips of Zea mays (L.)

In excised pro_1-1 mutant and corresponding normal type roots of Zea mays L. the uptake and interconversion of [¹⁴C]proline, [¹⁴C]glutamic acid, [¹⁴C]glutamine, and [¹⁴C]ornithine and their utilization for protein synthesis was measured with the intention of finding an explanation for the proline requirement of the mutant. Uptake of these four amino acids, with the exception of proline, was the same in mutant and normal roots, but utilization differed. Higher than normal utilization rates for proline and glutamic acid were noted in mutant roots leading to increased CO₂ production, free amino acid interconversion, and protein synthesis. Proline was synthesized from either glutamic acid (or glutamine) or ornithine in both mutant and normal roots; it did not accumulate but rather was used for protein synthesis. Ornithine was not a good precursor for proline in either system, but was preferentially converted to arginine and glutamine, particularly in mutant roots. The pro_1-1 mutant was thus not deficient in its ability to make proline. Based on these findings, and on the fact that ornithine, arginine, glutamic acid and aspartic acid are elevated as free amino acids in mutant roots, it is suggested that in the pro_1-1 mutant proline catabolism prevails over proline synthesis.     

Mechanism of plant growth stimulation by naphthenic Acid: effects on nitrogen metabolism of phaseolus vulgaris L

Fourteen-day-old Phaseolus vulgaris L. cv. Top Crop (bush bean) plants were sprayed with the plant growth stimulant, potassium naphthenate (20 mm). Seven days after treatment the contents of glutamic acid dehydrogenase, glutamic-oxaloacetic transaminase, nitrate reductase, glutamine synthetase, and cytochrome oxidase in the trifoliate leaf blades of treated plants were significantly larger, and the specific activity of the last four was significantly greater. Potassium nephthenate (1 μm) in the assay solutions did not significantly alter the activity of these enzymes in the cell-free extracts of untreated plants. Leaf discs from treated plants did not incorporate ¹⁴C-leucine into protein more actively. The protein content of leaves of treated plants was 15.3% greater, and the percentages of 16 individual amino acids in the hydrolysates of the proteins of control and treated plants showed numerous differences. The major changes were greater percentages of glutamic acid, glycine, and proline, and smaller values of arginine, lysine, tyrosine, and leucine in protein of treated plants. The content of ethanol-soluble (free) amino acids was greater by 7.5%. The principal changes in content of these acids were larger percentages of arginine and lysine, and smaller values for glutamic acid, serine, and proline in the leaves of potassium naphthenate-treated plants. The content of DNA, measured 1, 2, and 3 weeks after a foliar application of potassium naphthenate, was not significantly different from that of untreated plants, but the amount of RNA was significantly greater at all three times of measurement. The number and weight of green pods per plant 30 days after potassium naphthenate application were significantly larger, suggesting that the stimulative action of potassium naphthenate was in progress at the times of the assays. A mechanism, involving a genetic and a metabolic phase, is suggested for the stimulation of plant growth by naphthenate.     

Analysis of free amino acids during fermentation by Bacillus subtilis using capillary electrophoresis

A high performance capillary electrophoresis (HPCE) method was presented to identify and quantitate free amino acids during fermentation by Bacillus subtilis. Amino acids, pre-column derivatized with phenylisothicyanate, were separated and characterized by HPCE. In order to optimize separation conditions, the assay was developed by varying the β-cyclodextrin concentration and pH of the background electrolyte. A buffer system comprising 30 mM phosphate and 3 mM β-cyclodextrin at pH 7.0, voltage of 20 kV and detection wavelength of 254 nm showed the best results, with 17 out of 20 phenylthioncarbamyl amino acids in a solution adequately separated. For quantification, p-aminobenzoic acid was added as an internal standard. Analysis of free amino acids in Bacillus subtilis culture medium using this method revealed good consistency with the values obtained using conventional ninhydrin-based amino acid analyzer. Four free amino acids (aspartic acid, glutamic acid, proline, and tyrosine) concentration in an extracellular matrix during fermentation by Bacillus subtilis were mainly monitored using this method.     

Estimating the number of protein molecules in a plant cell: protein and amino acid homeostasis during drought

During drought stress, cellular proteostasis on the one hand and amino acid homeostasis on the other hand are severely challenged, because the decrease in photosynthesis induces massive proteolysis, leading to drastic changes in both the proteome and the free amino acid pool. Thus, we selected progressive drought stress in Arabidopsis (Arabidopsis thaliana) as a model to investigate on a quantitative level the balance between protein and free amino acid homeostasis. We analyzed the mass composition of the leaf proteome based on proteomics datasets, and estimated how many protein molecules are present in a plant cell and its subcellular compartments. In addition, we calculated stress-induced changes in the distribution of individual amino acids between the free and protein-bound pools. Under control conditions, an average Arabidopsis mesophyll cell contains about 25 billion protein molecules, of which 80% are localized in chloroplasts. Severe water deficiency leads to degradation of more than 40% of the leaf protein mass, and thus causes a drastic shift in distribution toward the free amino acid pool. Stress-induced proteolysis of just half of the 340 million RubisCO hexadecamers present in the chloroplasts of a single mesophyll cell doubles the cellular content of free amino acids. A major fraction of the amino acids released from proteins is channeled into synthesis of proline, which is a compatible osmolyte. Complete oxidation of the remaining fraction as an alternative respiratory substrate can fully compensate for the lack of photosynthesis-derived carbohydrates for several hours.

A quantitative perspective on the protein and amino acid composition of a leaf cell illustrates the dimension and specific consequences of massive proteolysis induced by severe water deficit.     

Salinity Stress and the Content of Proline in Roots of Pisum sativum and Tamarix tetragyna

Amino acid composition of the free amino acid pool and the TCA-insolubleprotein fraction were investigated in root tips of pea and Tamarixtetragyna plants grown at various levels of NaCl salinity. Salinitystress induced an increase of proline content, mainly in thefree amino acid pool in both plants, and of proline or hydroxyprolinecontent in the protein. Externally-supplied proline was absorbedand incorporated into protein, by pea roots, more effectivelythan by Tamarix roots. Salinity stress, apparently, stimulatedthe metabolism of externally-supplied labelled proline. Pearoots have a very large pool of free glutamic acid; however,70 per cent of the ¹⁴C from externally-supplied ¹⁴C-U-glutamicacid was released as CO₂. Very small amounts of it were incorporatedinto protein. No measurable amount of radioactivity could bedetected in any one of the individual amino acids, either ofprotein hydrolysate or the free amino acid pool. Proline very effectively counteracted the inhibitory effectof NaCl on pea seed germination and root growth. A similar effectbut to a lesser degree was achieved with phenylalanine and asparticacid. The feasibility of proline being a cytoplasmic osmoticumis discussed.     

Distribution of amino acids in the cellular fractions ofStaphylococcus aureus

WhenStaphylococcus aureus cells were labeled with a single radioactive amino acid for 20 minutes, the highest activity, except for alanine, leucine, and glycine, was found in the free pool. Significant amounts of the above amino acids and also valine and methionine were incorporated into the protein — cell wall fraction.Cells previously labeled with a single amino acid underwent a net loss of radioactivity when transferred to buffer, glucose, or complete medium. An exception was glycine. The greatest loss in activity occurred in the free pool.While some amino acids (alanine, cystine) were transferred from the free pool to the protein — cell wall fraction under all conditions tested, others (glutamic acid, proline) were transferred only under conditions of growth.Cells labeled with certain single amino acids and then transferred to a complete medium lost a significant portion of the label. The most extreme case noted was proline, but other amino acids also effluxed from the cell under these conditions.     

Metabolic profiling, free-radical scavenging and tyrosinase inhibitory activities of Lemna minor whole plants cultivated in various concentrations of proline and sucrose

Metabolic profiling of Lemna minor whole plants cultivated in proline and sucrose at various concentrations was performed using gas chromatography-mass spectrometry coupled with multivariate statistical analysis. In total, 46 compounds including alkaloids, amino acids, fatty acids, organic acids, phenolics, phytosterols, purines, and sugars were assigned, and the relative levels of these metabolites were compared in the L. minor whole plant samples. Free-radical scavenging and tyrosinase inhibitory activities were also investigated in L. minor whole plants cultivated in proline and sucrose at various concentrations. The whole plants cultivated in 3% sucrose and 0.5 mM proline for 42 days exhibited the highest antioxidative and tyrosinase inhibitory activities, and biomass accumulation. Total phenolic content and cinnamic acid content were also highest under those conditions, which might have contributed to the free-radical scavenging and tyrosinase inhibitory activities. There were strong correlations between free-radical scavenging activity and total phenolic content, and between tyrosinase inhibition activity and cinnamic acid content in L. minor whole plants cultivated under various conditions.     

Thin layer chromatographic analyses of amino acids in Echinostoma revolutum (Trematoda) adults

Bailey R. S. Jr. and Fried B. 1977. Thin layer Chromatographic analyses of amino acids in Echinostoma revolutum (Trematoda) adults. International Journal for Parasitology7: 497–499. Thin layer Chromatographic analyses were made on free pool amino acids and those obtained from the incubate fluid of Echinostoma revolutum adults maintained in a non-nutrient salt solution. The major free pool amino acids detected were alanine, proline, serine and methionine. Alpha-amino-n-butyric acid was also tentatively identified. Amino acids detected in the incubate fluid were leucine-isoleucine, valine, methionine, tyrosine, proline, alanine, glutamic acid, serine, arginine, and aplha-amino-n-butyric acid was also tentatively identified. Amino acids presumably isolated from either worm egesta or the protonephridial system were qualitively similar to those obtained from worm incubate fluid.     

Effect of sound and Lenzites-decayed wood on the amino acid composition of Reticulitermes flavipes

In hydrolysates of the eastern subterranean termite, Reticulitermes flavipes, the most abundant protein amino acids (μmoles) were glycine, alanine, and glutamic acid; the least abundant were methionine and histidine. Sawdust from both sound and Lenzites trabea-decayed sapwood blocks of sugar maple, loblolly pine, and slash pine was force-fed to termites. A diet of decayed rather than sound wood had little effect on protein amino acid composition of the termites; glycine content varied the most. In contrast, diet affected the free amino acid composition. Except for glutamic acid, the major protein amino acids of the termites were not the predominant free amino acids. Tyrosine and histidine were relatively more abundant as free than as protein amino acids. Greatest differences in protein amino acid compositions of sound and decayed wood were in contents of glycine, leucine, lysine, and arginine.