METABOLISM OF GLUTAMIC ACID AND RELATED AMINO ACIDS IN THE BRAIN STUDIED WITH 14C-LABELLED GLUCOSE, BUTYRIC ACID AND GLUTAMIC ACID IN HYPERCAPNIC RATS

Abstract— The influence of hypercapnia on the metabolism of glutamic acid, aspartic acid, glutamine and GABA in rat brain was studied using three different precursors. Acute hypercapnia induced a fall in the concentration of glutamic and aspartic acid, and a rise in the concentration of glutamine and GABA. Acute hypercapnia had a profound effect on the relative specific radioactivity of glutamine indicating that the excess glutamine, present in the brain in hypercapnia, was synthetized from glutamic acid in the compartment where it could become quickly labelled from butyric and glutamic acid, but not from glucose. This effect was maintained in chronic hypercapnia.     

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.     

THE EFFECTS OF 4-HYDROXYBUTYRIC ACID ON THE BIOSYNTHESIS OF AMINO ACIDS IN THE CENTRAL NERVOUS SYSTEM

—The effect of 4-hydroxybutyrate (GHB) on cerebral glucose metabolism has been studied. GHB increases the glucose level, decreases the lactate concentration and diminishes the incorporation of glucose carbon into glutamic acid, glutamine, aspartic acid and GABA in the brain of the rat in a state of general anaesthesia. The data reported here suggest that GHB interferes in the metabolism of glucose in brain.     

Free amino acids in the spinal cord, ganglia and ischiadic nerve of the dog after ligature of the abdominal aorta

The effect of occlusion of the abdominal aorta for 10, 20 and 40 minutes on the concentration of aspartic and glutamic acids, glutamine, glycine, alanine and gamma-amino butyric acid in the anterior and posterior horns of the lumbosacral spinal cord was studied in the dog, further, concentration of amino acids (except GABA) in lumbosacral spinal ganglia and in the ischiadic nerve following 40 minutes of occlusion. The changes were most marked after 40 minutes of occlusion with a rise in concentration of alanine, glutamine and glutamic acid in the dorsal part of grey matter. Striking was also the simultaneous elevated concentration of Glu and Gln in spinal ganglia. The significance of these changes is discussed from the aspect of metabolism and function of nerve cells. Under physiological conditions the free amino acid pool in the central nervous system remains essentially constant. Under pathological conditions, however, like ischemic-hypoxic states, various changes occur.     

Free Amino Acids in Cigarette Smoke (I)–(II)

Free amino acids in the cigarette smoke, produced in constant-volume continuous smoking by the use of an artificial smoking-device, have been paper-chromatographically studied, and twelve amino acids, i.e., α-alanine, β-alanine, glycine, glutamic acid, glutamine, serine, γ-amino butyric acid, valine, leucine, aspartic acid, proline, and ornithine(?) were qualitatively identified. Besides these amino acids, the presence of the other two unidentified ninhydrin-positive substances was observed. The presence of ten amino acids, other than glutamic acid and glutamine, has not yet been reported in the literature concerning tobacco smoke.     

Effect of nicotine on the level of extracellular amino acids in the hippocampus of rat

Using microdialysis, we compared intracerebral and subcutaneous administration of nicotine for the effect on the levels of extracellular amino acids in the hippocampus of anesthetized rats. Administration by microdialysis of 10 mM nicotine, resulting in a nicotine concentration of 0.134 μmol/g in the hippocampus, increased the extracellular levels of aspartic acid, glutamic acid, and serine by 26–60%. At 50 mM nicotine the increases in the levels of aspartic acid, glutamic acid, serine, glycine, and glutamine were between 76% and 141%. Subcutaneous administration of nicotine at a dose of 6 μmol/kg caused a 57% increase in the extracellular level of glutamic acid. After a dose of 12 μmol/kg that resulted in a nicotine level of 0.015 μmol/kg in the hippocampus, the extracellular level of glutamic acid was increased by 100%, and that of aspartic acid by 24%. Thus, higher cerebral nicotine levels were needed with intracerebral than with subcutaneous administration to obtain similar amino acid changes. Prior administration of mecamylamine or L-kynurenine prevented the subcutaneous nicotine-induced elevation of the extracellular levels of aspartic acid and glutamic acid. Our results indicate that receptor interactions modulate nicotine effects and that both nicotinic cholinergic and NMDA/glycine glutamatergic receptors participate in the action of nicotine in increasing extracellular amino acid levels.     

Effects of induced hypothermia on amino acids and glycogen in rat brain

Abstract— The concentrations of free amino acids and glycogen in the cerebral cortex of normal and deeply hypothermic (body temperature 18–20°C) rats were measured. The significant changes which accompanied the induction of hypothermia were a large reduction in glutamic acid concentration and moderate increases in the concentrations of glutamine and aspartic acid. The concentrations of γ-aminobutyric acid, N-acetylaspartic acid and glycogen did not change significantly.     

Interaction between Glu-219 and His-245 within the a subunit of F1F0-ATPase in Escherichia coli

Oligonucleotide-directed mutagenesis was used to generate mutations in the a subunit gene (uncB) altering the glutamic acid 219 and the histidine 245 codons. Substitutions of aspartic acid, glutamine, histidine, and leucine for glutamic acid at position 219 neither alter the hydrolytic activity of membrane-bound F1 nor the association of F1 with F0. However, the efficiency of F0-mediated proton translocation was reduced to varying degrees. Replacement of glutamic acid 219 with leucine reduced the ATP-driven proton pumping activity of intact F1F0 to undetectable levels. Roughly 5% of normal activity was observed when glutamine occupied position 219. Surprisingly higher activity, approaching 20% of wild type levels, is seen when histidine replaced glutamic acid 219. The aspartic acid substitution resulted in little loss of enzyme function. Substitution of glutamic acid for histidine 245 results in a reduction to about 45% of normal proton translocation. Construction of the double mutant with substitution of histidine at position 219 and glutamic acid at position 245 yields a complex with better proton translocation than with either mutant separately. The possibility that a functionally important interaction between histidine 245 and glutamic acid 219 of the a subunit may be directly involved in the proton translocation mechanism of F1F0-ATP synthase is discussed.     

Effect of coordinated addition of specific amino acids on the synthesis of recombinant glucose isomerase

The amplified expression of a recombinant protein is known to lead to an intracellular depletion of specific amino acid pools which in turn may affect the production of the desired protein. In order to counteract and overcome such a situation during the fermentation of the recombinant Escherichia coli (PMSG27) containing the glucose isomerase (GI) gene from Streptomyces sp. NCIM 2730, the effect of addition of different amino acids on the specific activity of GI was studied. The amino acid composition of GI from Streptomyces sp. NCIM 2730 reveals predominantly aspartic acid, glutamic acid, and glycine; therefore, in the present paper, the effect of coordinated addition of the assorted combinations of these three amino acids on the synthesis of recombinant GI was studied. The results were analyzed using a 2³ factorial design. The following conclusions were derived from the analysis of two-factor interactions of the three amino acids: (i) The interaction between the aspartic and glutamic acid is independent of aspartic acid concentration but is affected by the increasing concentrations of glutamic acid, (ii) The effect of aspartic acid concentration is more than that of glycine, and (iii) During the interaction of glutamic acid and glycine, the effect of glutamic acid is more prominent than that of glycine. The three-factor interaction analyses reveal that the effect of the three amino acids is in the order aspartic acid > glutamic acid > glycine.     

Different binding sites for entry and exit of amino acids in whole cells of Mycobacterium phlei.

On the basis of mutual inhibition of uptake with different amino acids in whole cells of Mycobacterium phlei, it was demonstrated that the binding site of proline was different from those of all other amino acids studied. Other groups of amino acids share a common binding site: lysine, histidine, and arginine; valine, leucine, and isoleucine; tryptophan, tyrosine, and phenylalanine; glutamic acid and aspartic acid. The exit and entry processes were studied for proline, glutamine, and glutamic acid. It was observed that in each case the entry and exit processes were mediated by different membrane sites.     

Effect of amino acids on rooting of apple dwarf rootstocksin vitro

The effect of twelve amino acids and lactalbumin hydrolysate in concentration of 200 mg 1^?1 on rooting of the dwarf apple rootstocks P 2 and P 60 was testedin vitro. Arginine, omithine, glutamic acid and glycine enhanced root number of the P 60 rootstock; proline and lactalbumin hydrolysate were neutral; and asparagine, tyrosine, methionine, cysteine and glutamine lowered the root number. Tyrosine, methionine, cysteine and glutamine reduced almost completely rooting of P 60. In the recalcitrant P 2 rootstock aspartic acid, glutamic acid and omithine significantly enhanced the number of roots and rooted shoots, arginine and tryptophan increased the root number only slightly, asparagine was neutral, and proline reduced the root number.     

Influence of Several Growth Regulators and Amino Acids on in vitro Organogenesis of Torenia fournieri Lind.

The effects of several growth regulators and amino acids onin vitro organogenesis of Torenia fournieri Lind. were determinedusing internodal segments. Treatment with 2,4-D¹ resulted innodular callus formation, while NAA and IAA induced roots constantlybut much less frequently shoot buds. Individually BA, zeatin,and 4-PU induced bud formation, but these shoot buds did notdevelop further. Formation of buds by cytokinin was influencedby a simultaneous application of NAA or 2,4-D, but not of IAA,its degree being reduced when BA was simultaneously appliedwith NAA or 2,4-D. When zeatin or kinetin was added with NAA,numerous roots were induced. The effects of various L-amino acids on in vitro organogenesiswere also investigated using the defined medium in which KNO₃was a principal source of nitrogen. The formation of buds wasconsiderably stimulated by alanine and asparagine, and slightlyby glutamic acid in the medium containing both NAA and BA, inwhich bud formation was easily induced. On the other hand, allamino acids except for glutamic acid and aspartic acid inhibitedroom formation in this medium. Root formation was greatly stimulated by proline, alanine, glutamine,glutamic acid, and aspartic acid, and slightly by arginine andtryptophan in the medium containing NAA but no BA. Glutamicacid and aspartic acid also enhanced bud formation in this medium.     

Changes in the Free Amino Compounds in Young Tomato Plants in Light and Darkness with particular Reference to {gamma}-Aminobutyric Acid

Tomato plants were grown to the five-leaf stage under uniformconditions in a growth room with a daily light period of 15h. Plants were sampled at intervals through 24 h periods andthe free ninhydrin-positive compounds determined in roots, bleedingsap, stems and shoots (mainly leaves), using ion-exchange columnchromatography and a lithium-buffer separation system. The compoundspresent and their range of concentrations are given for twooccasions: after illumination for 8 hand after 5 h of darkness. Data for -aminobutyric acid (GAB), glutamic acid, glutamine,alanine, aspartic acid and ammonia are summarized graphicallyfor all occasions and for all parts of the plant; asparaginefor sap only. The data were examined for correlations betweenthese substances for both light and dark conditions. Relative amounts of free acids were: root glutamine> glutamicand GAB > aspartic > alanine; bleeding sap glutamine >asparagine > GAB > aspartic> alanine; stem glutamine> glutamic > GAB and aspartic > alanine; shoot (leaf)GAB and glutamine > aspartic > alanine and glutamic. Patternsof change were as follows: in the root GAB and glutamic weresimilar and unlike glutamine; alanine did not change;sap ammonia,GAB and alanine were parallel, glutamine was similar to theseonly in light; in the stem glutamine and glutamic tended toaccumulate in parallel in light, but GAB did not; in the shoot(leaf) GAB and glutamine were similar except that the formeraccumulated more rapidly in the initial light period; glutamicacid and alanine were similar to each other but distinct fromGAB and glutamine. The relatively large amounts of GAB in tomato plants and themagnitude of the changes occurring in light and darkness seemindicative of its importance as a temporary storage productfor protein amino acids, but the factors controlling accumulationand utilization in different parts of the plant are unknown.     

Changes in the Nitrogen Compounds of Xylem Sap of Mulberry (Morus alba L.) during Regrowth after Pruning

Changes in fresh and dry weights and total nitrogen in stemsections of mulberry (Morus alba L.) and seasonal fluctuationin the amounts of exudate, pH and nitrogen compounds in xylemsap from cut stems of the plant after pruning have been studied.The amount and concentrations of nitrogen compounds in the sapchanged during the experimental period, but nitrate-nitrogenand ammonia-nitrogen were constant constituents, and asparaginewas quantitatively the major organic nitrogen compound. Smalleramounts of glutamine, aspartic acid and glutamic acid were alsofound, but no ureides or alkaloids were detected. Relationshipsbetween growth and nitrogen in xylem sap of mulberry and therole and importance of asparagine in nitrogen metabolism arediscussed. Morus alba L., mulberry, asparagine, exudates, nitrogen, amino-acids, xylem sap, stem growth, aspartic acid, glutamic acid, ureides     

A kinetic study of the assimilation of 15N-labelled ammonium in rice seedling roots

The pathway of ammonium nitrogen assimilation, its incorporationinto amino acids and synthesis of protein was studied with theaid of nitrogen-15. The analysis of ¹⁵N involves the use ofoptical emission spectrometry. Kinetic analysis of nitrogen assimilation by the roots indicatesthat glutamine and glutamic acid were the primary products ofammonium assimilation. Possibly some of the amino acids, suchas aspartic acid and alanine received their amino nitrogen directlyfrom free ammonia in the roots. Amino groups were transformedinto other amino acids from these primary products, especiallyfrom glutamic acid through transamination. (Received April 1, 1974; )     

LEVELS OF AMINO ACIDS AND PROTEINS IN PACINIAN CORPUSCLES OF THE CAT

Abstract— Paper chromatography of extracts from mesenteric Pacinian corpuscles of the cat revealed the presence of glutamic acid, glutamine, aspartic acid and alanine as major amino acids, and glycine, serine and threonine in traces; GABA was not detected. Levels of glutamic acid (0·75 μmol/g ' 0·37, s.d. ), glutamine (1·34 ± 0·55), and aspartic acid (0·32 ± 0·22) of mesenteric and pancreatic samples of Pacinian corpuscles were determined by separation on chromatographic columns. The protein values averaged 5·2 ± 0·66 per cant of the wet weight.
Treatment of the cats with reserpine or pargyline or deafferentation of the Pacinian corpuscles did not significantly alter these values.     

Effect of glutamic acid on the anaerobic formation of ATP in the heart muscle

The effect of exogenous glutamic acid on nitrogenous and energetic metabolism of isolated perfused heart of the rat was studied under anoxia. Addition of 5 mM glutamic acid to the perfusate significantly increased the ATP level in anoxic heart. Perfusion of anoxic heart with 5 mM glutamic acid recovered the glutamate and aspartate tissue content and caused augmented production of alanine and succinate, while lactate formation did not change. In the presence of glutamic acid, the glutamine and asparagine contents in the heart-perfusate system markedly increased; however, the ammonia content did not reduce significantly. The effect on glutamic acid was reproduced by its transamination products, 5 mM aspartic and 5 mM alpha-ketoglutaric acids, and was totally eliminated by 2 mM aminooxyacetic acid, an inhibitor of transaminases. These data suggest that the glutamate-induced protective effect of ATP is probably related to the stimulation of substrate phosphorylation in mitochondria, resulting in succinate synthesis that is coupled with glutamate transamination.     

Site-directed mutagenesis of catalytic active-site residues of Taka-amylase A.

The cDNA encoding Taka-amylase A (EC.3.2.1.1, TAA) was isolated to identify functional amino acid residues of TAA by protein engineering. The putative catalytic active-site residues and the substrate binding residue of TAA were altered by site-directed mutagenesis: aspartic acid-206, glutamic acid-230, aspartic acid-297, and lysine-209 were replaced with asparagine or glutamic acid, glutamine or aspartic acid, asparagine or glutamic acid, and phenylalanine or arginine, respectively. Saccharomyces cerevisiae strain YPH 250 was transformed with the expression plasmids containing the altered cDNA of the TAA gene. All the transformants with an expression vector containing the altered cDNA produced mutant TAAs that cross-reacted with the TAA antibody. The mutant TAA with alteration of Asp206, Glu230, or Asp297 in the putative catalytic site had no alpha-amylase activity, while that with alteration of Lys209 in the putative binding site to Arg or Phe had reduced activity.     

End products of glucose and glutamine metabolism by L929 cells

Products of glucose and glutamine metabolism by L929 cells were detected and quantitated by gas chromatography and mass spectrometry of the oxime-trimethylsilyl derivatives. This method allowed detection and identification of all major carboxylic and amino acids produced in the system. Although lactic acid was expected to be the major product, alanine, citric, glutamic, aspartic, and pyruvic acids were also released into the culture medium at significant rates. Incorporation of labeled carbon from D-[U-13C]glucose showed that the alanine, lactic, and pyruvic acids were derived from glucose as was one-third of the citric acid carbon. The rate of glucose utilization for production of these end products was 29-fold greater than the rate of glucose oxidation to CO2, and calculated ATP production from alanine and pyruvate synthesis exceeded that from lactate synthesis by nearly 2-fold. Utilization of glutamine for synthesis of aspartic, glutamic, and citric acids also exceeded the rate of glutamine oxidation, thereby making end-product synthesis from glucose and glutamine the dominant cellular metabolic activity. In the absence of glucose, synthesis and intracellular levels of aspartic and glutamic acids increased, whereas synthesis and cell content of the other acids decreased markedly. This response is consistent with the metabolic pattern proposed by Moreadith and Lehninger (Moreadith, R.W., and Lehninger, A.L. (1984) J. Biol. Chem. 259, 6215-6221) in which much of the glutamine used by these cells is converted to aspartate in the absence of a pyruvate source and to aspartate or citrate in the presence of pyruvate.