scholarly journals BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS

1972 ◽  
Vol 54 (2) ◽  
pp. 279-294 ◽  
Author(s):  
David C. Shephard ◽  
Wendy B. Levin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Technical Problems ◽  
Hydrolyzed Protein ◽  
Protein Amino Acids ◽  
Amino Acid Labeling ◽  
Labeling Pattern

The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.

Effect of Cycloheximide on In Vitro and In Vivo Protein Synthesis by Certain Tissues of Rats and Pigeons with Special Reference to Muscle

1973 ◽  
Vol 51 (12) ◽  
pp. 933-941 ◽  
Author(s):  
Njanoor Narayanan ◽  
Jacob Eapen
Keyword(s):  
Amino Acids ◽  
Body Weight ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Incorporation ◽  
Contrast Administration ◽  
Acid Incorporation ◽  
Tissue Homogenates

The effect of cycloheximide in vitro and in vivo on the incorporation of labelled amino acids into protein by muscles, liver, kidneys, and brain of rats and pigeons was studied. In vitro incorporation of amino acids into protein by muscle microsomes, myofibrils, and myofibrillar ribosomes was not affected by cycloheximide. In contrast, administration of the antibiotic into intact animals at a concentration of 1 mg/kg body weight resulted in considerable inhibition of amino acid incorporation into protein by muscles, liver, kidneys, and brain. This inhibition was observed in all the subcellular fractions of these tissues during a period of 10–40 min after the administration of the precursor. Tissue homogenates derived from in vivo cycloheximide-treated animals did not show significant alteration in in vitro amino acid incorporation with the exception of brain, which showed a small but significant enhancement.

scholarly journals Key role of l-alanine in the control of hepatic protein synthesis

1987 ◽  
Vol 241 (2) ◽  
pp. 491-498 ◽  
Author(s):  
D Pérez-Sala ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Physiological Role ◽  
Chain Elongation ◽  
Liver Protein ◽  
Isolated Liver Cells ◽  
Metabolic Transformation ◽  
Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

scholarly journals In vivo Determination of Amino Acid Bioavailability in Humans and Model Animals

2005 ◽  
Vol 88 (3) ◽  
pp. 923-934 ◽  
Author(s):  
Malcolm F Fuller ◽  
Daniel Tomé
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
The Body ◽  
Whole Body ◽  
Intestinal Lumen ◽  
Stable Isotope Labelling ◽  
Ileal Digestibility ◽  
Hydrolyzed Protein ◽  
Protein Free Diet

Abstract Because the digestion of many dietary proteins is incomplete, and because there is a continuous (but variable) entry into the intestinal lumen of endogenous protein and amino acid nitrogen that is also subject to digestion, the fluxes of nitrogen, amino acids, and protein in the gut exhibit a rather complicated pattern. Methods to distinguish and quantitate the endogenous and dietary components of nitrogen and amino acids in ileal chyme or feces include the use of a protein-free diet, the enzyme-hydrolyzed protein method, different levels of protein intake, multiple regression methods, and stable-isotope labelling of endogenous or exogenous amino acids. Assessment of bioavailability can be made, with varying degrees of difficulty, in man directly but, for routine evaluation of foods, the use of model animals is attractive for several reasons, the main ones being cost and time. Various animals and birds have been proposed as models for man but, in determining their suitability as a model, their physiological, enzymological, and microbiological differences must be considered. Fecal or ileal digestibility measurements, as well as apparent and true nitrogen and amino acid digestibility measurements, have very different nutritional significance and can, thus, be used for different objectives. Measurements at the ileal level are critical for determining amino acid losses of both dietary and endogenous origin, whereas measurements at the fecal level are critical in assessing whole-body nitrogen losses. A complementary and still unresolved aspect is to take into account the recycling of intestinal nitrogen and bacterial amino acids to the body.

scholarly journals Amino acid infusion increases the sensitivity of muscle protein synthesis in vivo to insulin. Effect of branched-chain amino acids

1988 ◽  
Vol 254 (2) ◽  
pp. 579-584 ◽  
Author(s):  
P J Garlick ◽  
I Grant
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain

Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.

Control of Muscle Protein Synthesis as a Result of Contractile Activity and Amino Acid Availability: Implications for Protein Requirements

2001 ◽  
Vol 11 (s1) ◽  
pp. S170-S176 ◽  
Author(s):  
Michael J. Rennie
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Contractile Activity ◽  
Muscle Protein Synthesis ◽  
Protein Requirements ◽  
Amino Acid Availability ◽  
Separate Pathway

The major anabolic influences on muscle are feeding and contractile activity. As a result of feeding, anabolism occurs chiefly by increases in protein synthesis with minor changes in protein breakdown. Insulin has a permissive role in increasing synthesis, but the availability of amino acids is crucial for net anabolism. We have investigated the role of amino acids in stimulating muscle protein synthesis, the synergy between exercise and amino acid availability, and some of the signaling elements involved. The results suggest that muscle is acutely sensitive to amino acids, that exercise probably increases the anabolic effects of amino acids by a separate pathway, and that for this reason it is unlikely that accustomed physical exercise increases protein requirements.

Role of Leucine in Protein Metabolism During Exercise and Recovery

2002 ◽  
Vol 27 (6) ◽  
pp. 646-662 ◽  
Author(s):  
Donald K. Layman
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Branched Chain Amino Acids ◽  
New Findings ◽  
Branched Chain

Exercise produces changes in protein and amino acid metabolism. These changes include degradation of the branched-chain amino acids, production of alanine and glutamine, and changes in protein turnover. One of the amino acid most affected by exercise is the branched-chain amino acid leucine. Recently, there has been an increased understanding of the role of leucine in metabolic regulations and remarkable new findings about the role of leucine in intracellular signaling. Leucine appears to exert a synergistic role with insulin as a regulatory factor in the insulin/phosphatidylinositol-3 kinase (PI3-K) signal cascade. Insulin serves to activate the signal pathway, while leucine is essential to enhance or amplify the signal for protein synthesis at the level of peptide initiation. Studies feeding amino acids or leucine soon after exercise suggest that post-exercise consumption of amino acids stimulates recovery of muscle protein synthesis via translation regulations. This review focuses on the unique roles of leucine in amino acid metabolism in skeletal muscle during and after exercise. Key words: branched-chain amino acids, insulin, protein synthesis, skeletal muscle

scholarly journals Effects of p-chlorophenylalanine and α-methylphenylalanine on amino acid uptake and protein synthesis in mouse neuroblastoma cells

1978 ◽  
Vol 174 (3) ◽  
pp. 931-938 ◽  
Author(s):  
C J Kelly ◽  
T C Johnson
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Animal Models ◽  
Phenylalanine Hydroxylase ◽  
Present Report ◽  
Neuroblastoma Cells ◽  
Acid Uptake

The phenylalanine analogues p-chlorophenylalanine and alpha-methylphenylalanine were used to inhibit phenylalanine hydroxylase in animal models for phenylketonuria. The present report examines the affects of these analogues on the metabolism of neuroblastoma cells. p-Chlorophenylalanine inhibited growth and was toxic to neuroblastoma cells. Although in vivo this analogue increased cell monoribosomes by 42%, it did not significantly affect poly(U)-directed protein synthesis in vitro. P-Chlorophenylalanine did not compete with phenylalanine or tyrosine for aminoacylation of tRNA and was therefore not substituted for those amino acids in nascent polypeptides. The initial cellular uptake of various large neutral amino acids was inhibited by this analogue but did not affect the flux of amino acids already in the cell; this suggested that an alteration of the cell's amino acid pools was not responsible for the cytotoxicity of the analogues. In contrast with p-chlorophenylalanine, alpha-methylphenylalanine did not exert these direct toxic effects because the administration of alpha-methylphenylalanine in vivo did not affect brain polyribosomes and a comparable concentration of this analogue was neither growth inhibitory nor cytotoxic to neuroblastoma cells in culture. The suitability of each analogue as an inhibitor of phenylalanine hydroxylase in animal models for phenylketonuria is discussed.

scholarly journals Amino Acid Metabolism in Apicomplexan Parasites

Metabolites ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 61
Author(s):  
Aarti Krishnan ◽  
Dominique Soldati-Favre
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Current Knowledge ◽  
Acid Biosynthesis ◽  
Apicomplexan Parasites ◽  
Obligate Intracellular ◽  
Metabolic Functions ◽  
Transcriptomics Data

Obligate intracellular pathogens have coevolved with their host, leading to clever strategies to access nutrients, to combat the host’s immune response, and to establish a safe niche for intracellular replication. The host, on the other hand, has also developed ways to restrict the replication of invaders by limiting access to nutrients required for pathogen survival. In this review, we describe the recent advancements in both computational methods and high-throughput –omics techniques that have been used to study and interrogate metabolic functions in the context of intracellular parasitism. Specifically, we cover the current knowledge on the presence of amino acid biosynthesis and uptake within the Apicomplexa phylum, focusing on human-infecting pathogens: Toxoplasma gondii and Plasmodium falciparum. Given the complex multi-host lifecycle of these pathogens, we hypothesize that amino acids are made, rather than acquired, depending on the host niche. We summarize the stage specificities of enzymes revealed through transcriptomics data, the relevance of amino acids for parasite pathogenesis in vivo, and the role of their transporters. Targeting one or more of these pathways may lead to a deeper understanding of the specific contributions of biosynthesis versus acquisition of amino acids and to design better intervention strategies against the apicomplexan parasites.

In vivo regulation of phenylalanine hydroxylation to tyrosine, studied using enrichment in apoB-100

2008 ◽  
Vol 294 (2) ◽  
pp. E475-E479 ◽  
Author(s):  
Mahroukh Rafii ◽  
Jane M. McKenzie ◽  
Susan A. Roberts ◽  
George Steiner ◽  
Ronald O. Ball ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Isotope Ratio Mass Spectrometry ◽  
Break Point ◽  
Adult Men ◽  
Plasma Phenylalanine ◽  
Independent Verification

Phenylalanine hydroxylation is necessary for the conversion of phenylalanine to tyrosine and disposal of excess phenylalanine. Studies of in vivo regulation of phenylalanine hydroxylation suffer from the lack of a method to determine intrahepatocyte enrichment of phenylalanine and tyrosine. apoB-100, a hepatic export protein, is synthesized from intrahepatocyte amino acids. We designed an in vivo multi-isotope study, [15N]phenylalanine and [2H2]tyrosine to determine rates of phenylalanine hydroxylation from plasma enrichments in free amino acids and apoB-100. For independent verification of apoB-100 as a reflection of enrichment in the intrahepatocyte pool, [1-13C]lysine was used as an indicator amino acid (IAA) to measure in vivo changes in protein synthesis in response to tyrosine supplementation. Adult men ( n = 6) were fed an amino acid-based diet with low phenylalanine (9 mg·kg−1·day−1, 4.54 μmol·kg−1·,h−1) and seven graded intakes of tyrosine from 2.5 (deficient) to 12.5 (excess) mg·kg−1·day−1. Gas chromatography-quadrupole mass spectrometry did not detect any tracer in apoB-100 tyrosine. A new and more sensitive method to measure label enrichment in proteins using isotope ratio mass spectrometry demonstrated that phenylalanine hydroxylation measured in apoB-100 decreased linearly in response to increasing tyrosine intake and reached a break point at 6.8 mg·kg−1·day−1. IAA oxidation decreased with increased tyrosine intake and reached a break point at 6.0 mg·kg−1·day−1. We conclude: apoB-100 is an accurate and useful measure of changes in phenylalanine hydroxylation; the synthesis of tyrosine via phenylalanine hydroxylation is regulated to meet the needs for protein synthesis; and that plasma phenylalanine does not reflect changes in protein synthesis.

Sign in / Sign up

Export Citation Format

Share Document