Amino Acid and Protein Metabolism During Differentiation (Sclerotization) of the Myxomycete Physarum flavicomum

1975 ◽  
Vol 53 (8) ◽  
pp. 834-843 ◽  
Author(s):  
Henry R. Henney Jr. ◽  
Glenna Maxey
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Metabolism ◽  
Cellular Proteins ◽  
Transport Systems ◽  
Differentiation Process ◽  
Cell Pool ◽  
Intracellular Amino Acids ◽  
Differentiation Period

Protein synthesized by growing plasmodia of Physarum flavicomum was steadily degraded when the plasmodia were induced to differentiate (form sclerotia). Protein synthesis occurred during the initial one-fifth (9 h) of the 48 h differentiation period, but most of this protein was also degraded shortly after its synthesis. Amino acids were primary catabolites during the differentiation process, and catabolism was extensive, even in the presence of dextrose. Glutamic acid was catabolized at a rate about two and a half or three times greater, respectively, than that observed for valine and arginine. Active transport systems for amino acids appeared to be present and to remain functional in P. flavicomum during differentiation. Amino acids included in the sclerotization media were rapidly accumulated into the cell pool and protein fractions. Intracellular amino acids were actively retained and were not released into the medium during differentiation.Differentiation of this Myxomycete, therefore, is characterized by a change in the metabolism of the sclerotizing plasmodium to an autolytic type, as cellular proteins and amino acids are actively catabolized during the formation of the dormant sclerotia.

Whole body protein kinetics in women: effect of pregnancy and IDDM during anabolic stimulation

2000 ◽  
Vol 279 (5) ◽  
pp. E978-E988 ◽  
Author(s):  
Paul G. Whittaker ◽  
Choy H. Lee ◽  
Roy Taylor
Keyword(s):  
Amino Acids ◽  
Type 1 Diabetes ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Metabolism ◽  
Whole Body ◽  
Protein Breakdown ◽  
Body Protein ◽  
In Pregnancy

The effects of pregnancy and type 1 diabetes [insulin-dependent diabetes mellitus (IDDM)] on protein metabolism are still uncertain. Therefore, six normal and five IDDM women were studied during and after pregnancy, using [13C]leucine and [2H5]phenylalanine with a hyperinsulinemic-euglycemic clamp and amino acid infusion. Fasting total plasma amino acids were lower in pregnancy in normal but not IDDM women (2,631 ± 427 vs. 2,057 ± 471 and 2,523 ± 430 vs. 2,500 ± 440 μmol/l, respectively). Whole body protein breakdown (leucine) increased in pregnancy [change in normal (ΔN) and IDDM women (ΔD) 0.59 ± 0.40 and 0.48 ± 0.26 g · kg−1 · day−1, both P < 0.001], whereas reductions in protein breakdown due to insulin/amino acids (ΔN −0.57 ± 0.19, ΔD −0.58 ± 0.20 g · kg−1 · day−1, both P < 0.001) were unaffected by pregnancy. Protein breakdown in IDDM women was not higher than normal, and neither pregnancy nor type 1 diabetes altered the insulin sensitivity of amino acid turnover. Nonoxidized leucine disposal (protein synthesis) increased in pregnancy (ΔN 0.67 ± 0.45, ΔD 0.64 ± 0.34 g · kg−1 · day−1, both P < 0.001). Pregnancy reduced the response of phenylalanine hydroxylation to insulin/amino acids in both groups (ΔN −1.14 ± 0.74, ΔD −1.12 ± 0.77 g · kg−1 · day−1, both P < 0.05). These alterations may enable amino acid conservation for protein synthesis and accretion in late pregnancy. Well-controlled type 1 diabetes caused no abnormalities in the regulation of basal or stimulated protein metabolism.

scholarly journals Amino Acid Concentrations and Protein Metabolism of Two Types of Rat Skeletal Muscle in Postprandial State and After Brief Starvation

2017 ◽  
pp. 959-967 ◽  
Author(s):  
M. HOLEČEK ◽  
S. MIČUDA
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Metabolism ◽  
Cathepsin B ◽  
Fed State ◽  
Postprandial State ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Amino Acid Concentrations

We have investigated amino acid concentrations and protein metabolism in musculus extensor digitorum longus (EDL, fast-twitch, white muscle) and musculus soleus (SOL, slow-twitch, red muscle) of rats sacrificed in the fed state or after one day of starvation. Fractional protein synthesis rates (FRPS) were measured using the flooding dose method (L-[3,4,5-3H]phenylalanine). Activities of two major proteolytic systems in muscle (the ubiquitin-proteasome and lysosomal) were examined by measurement of chymotrypsin like activity of proteasome (CTLA), expression of ubiquitin ligases atrogin-1 and muscle-ring-finger-1 (MuRF-1), and cathepsin B and L activities. Intramuscular concentrations of the most of non-essential amino acids, FRPS, CTLA and cathepsin B and L activities were in postprandial state higher in SOL when compared with EDL. The differences in atrogin-1 and MuRF-1 expression were insignificant. Starvation decreased concentrations of a number of amino acids and increased concentrations of valine, leucine, and isoleucine in blood plasma. Starvation also decreased intramuscular concentrations of a number of amino acids differently in EDL and SOL, decreased protein synthesis (by 31 % in SOL and 47 % in EDL), and increased expression of atrogin-1 and MuRF-1 in EDL. The effect of starvation on CTLA and cathepsin B and L activities was insignificant. It is concluded that slow-twitch (red) muscles have higher rates of protein turnover and may adapt better to brief starvation when compared to fast-twitch (white) muscles. This phenomenon may play a role in more pronounced atrophy of white muscles in aging and muscle wasting disorders.

scholarly journals Misincorporation of free m-tyrosine into cellular proteins: a potential cytotoxic mechanism for oxidized amino acids

2006 ◽  
Vol 395 (2) ◽  
pp. 277-284 ◽  
Author(s):  
Hande Gurer-Orhan ◽  
Nuran Ercal ◽  
Suneetha Mare ◽  
Subramaniam Pennathur ◽  
Hilmi Orhan ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Cho Cells ◽  
Chinese Hamster Ovary Cells ◽  
Trna Synthetase ◽  
Cellular Proteins ◽  
Alternative Mechanism ◽  
Tandem Mass Spectrometric

In vitro studies demonstrate that the hydroxyl radical converts L-phenylalanine into m-tyrosine, an unnatural isomer of L-tyrosine. Quantification of m-tyrosine has been widely used as an index of oxidative damage in tissue proteins. However, the possibility that m-tyrosine might be generated oxidatively from free L-phenylalanine that could subsequently be incorporated into proteins as an L-tyrosine analogue has received little attention. In the present study, we demonstrate that free m-tyrosine is toxic to cultured CHO (Chinese-hamster ovary) cells. We readily detected radiolabelled material in proteins isolated from CHO cells that had been incubated with m-[14C]tyrosine, suggesting that the oxygenated amino acid was taken up and incorporated into cellular proteins. m-Tyrosine was detected by co-elution with authentic material on HPLC and by tandem mass spectrometric analysis in acid hydrolysates of proteins isolated from CHO cells exposed to m-tyrosine, indicating that free m-tyrosine was incorporated intact rather than being metabolized to other products that were subsequently incorporated into proteins. Incorporation of m-tyrosine into cellular proteins was sensitive to inhibition by cycloheximide, suggesting that protein synthesis was involved. Protein synthesis using a cell-free transcription/translation system showed that m-tyrosine was incorporated into proteins in vitro by a mechanism that may involve L-phenylalanine-tRNA synthetase. Collectively, these observations indicate that m-tyrosine is toxic to cells by a pathway that may involve incorporation of the oxidized amino acid into proteins. Thus misincorporation of free oxidized amino acids during protein synthesis may represent an alternative mechanism for oxidative stress and tissue injury during aging and disease.

Human soleus and vastus lateralis muscle protein metabolism with an amino acid infusion

2005 ◽  
Vol 288 (3) ◽  
pp. E479-E485 ◽  
Author(s):  
Chad C. Carroll ◽  
James D. Fluckey ◽  
Rick H. Williams ◽  
Dennis H. Sullivan ◽  
Todd A. Trappe
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Resistance Exercise ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Vastus Lateralis ◽  
Translational Initiation ◽  
Acid Infusion ◽  
Amino Acid Infusion

The calf muscles, compared with the thigh, are less responsive to resistance exercise in ambulatory and bed-rested individuals, apparently due to muscle-specific differences in protein metabolism. We chose to evaluate the efficacy of using amino acids to elevate protein synthesis in the soleus, because amino acids have been shown to have a potent anabolic effect in the vastus lateralis. Mixed muscle protein synthesis in the soleus and vastus lateralis was measured before and after infusion of mixed amino acids in 10 individuals (28 ± 1 yr). Phosphorylation of ribosomal protein p70 S6 kinase (p70S6K; Thr389) and eukaryotic initiation factor 4E-binding protein-1 (4E-BP1; Thr37/46) was also evaluated at rest and after 3 h of amino acid infusion. Basal protein synthesis was similar ( P = 0.126), and amino acids stimulated protein synthesis to a similar extent ( P = 0.004) in the vastus lateralis (0.043 ± 0.011%/h) and soleus (0.032 ± 0.017%/h). Phosphorylation of p70S6K ( P = 0.443) and 4E-BP1 ( P = 0.192) was not increased in either muscle; however, the soleus contained more total ( P = 0.002) and phosphorylated ( P = 0.013) 4E-BP1 than the vastus lateralis. These data support the need for further study of amino acid supplementation as a means to compensate for the reduced effectiveness of calf resistance exercise in ambulatory individuals and those exposed to extended periods of unloading. The greater 4E-BP1 in the soleus suggests that there is a muscle-specific distribution of general translational initiation machinery in human skeletal muscle.

scholarly journals Relationship between intracellular amino acids and protein synthesis in the extensor digitorum longus muscle of rats

1969 ◽  
Vol 114 (2) ◽  
pp. 171-178 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Free Amino ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum Longus Muscle ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Intracellular Amino Acids ◽  
Free Amino Acid Pools

1. The incorporation into protein, and the accumulation into the free amino acid pools, of radioactive l-leucine and glycine was studied in rat extensor digitorum longus muscle. 2. The tissue was incubated first with 14C-labelled and then with 3H-labelled amino acid. 3. The experimental results were consistent with a model based on the premise that the amino acids in protein were incorporated directly from the extracellular pool.

scholarly journals The control by insulin of amino acid accumulation in muscle

1970 ◽  
Vol 117 (3) ◽  
pp. 457-465 ◽  
Author(s):  
K. L. Manchester
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Aminobutyric Acid ◽  
Technical Problems ◽  
Protein Uptake ◽  
Cell Pool ◽  
Acid Accumulation ◽  
Amino Acid Accumulation ◽  
Stimulation Of

1. The capacity of insulin to enhance the accumulation by muscle of several amino acids was studied. Reports that threonine uptake is enhanced by insulin were not confirmed, despite its enhanced incorporation into protein. Uptake of β-alanine and γ-aminobutyric acid also did not respond to the hormone. A stimulation of accumulation of alanine, histidine and ethionine was observed. 2. The capacity of inhibitors of protein synthesis to reveal a stimulation by insulin of accumulation of several amino acids, hitherto considered unresponsive to insulin in the absence of inhibitor, was confirmed. Cycloheximide was as effective as puromycin. However, two of these amino acids, alanine and histidine, here showed response to insulin in the absence of inhibitor. The presence of cycloheximide was found to enhance uptake of cycloleucine, ethionine and threonine; in its presence insulin enhanced uptake of β-alanine and α-methyltyrosine. 3. It is concluded that the influence of inhibitors of protein synthesis on amino acid accumulation and the response of amino acid accumulation to insulin are not adequately explained on the basis of inhibition of protein synthesis allowing amino acids to accumulate more readily. 4. The technical problems of whether linear rates of incorporation of amino acids into protein really indicate more than one cell pool are discussed and safeguards suggested. That initial rates of incorporation of label into protein are likely to be non-linear is shown.

On the Role of Branched-Chain Amino Acids in Protein Turnover of Skeletal Muscle. Studies in vivo with L-Norleucine

1985 ◽  
Vol 40 (5-6) ◽  
pp. 427-437 ◽  
Author(s):  
Klaus-Joachim Schott ◽  
Jochen Gehrmann ◽  
Ulla Potter ◽  
Volker Neuhoff
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Small Intestine ◽  
Amino Acid ◽  
Protein Metabolism ◽  
Protein Turnover ◽  
Protein Concentration ◽  
Amino Acid Concentrations

Abstract 1. The effect of ʟ-norleucine, an isomer of leucine, on protein metabolism in vivo was studied in suckling rats. Rats were injected subcutaneously with various doses of ʟ-norleucine (0.5 and 5.0 μmol/g body wt.) every 12 h from 3 to 15 days post partum. Protein concentration, amino acid concentrations, and incorporation of [3H]tyrosine into protein were analyzed in liver, muscles of thigh and small intestine. Amino acid concentrations and insulin levels in serum were also measured. 2. At 5 days of age, norleucine induced an increase in protein concentration of skeletal muscle with an increased incorporation of [3H]tyrosine into protein indicating an accelerated protein synthesis. Changes in protein metabolism were paralleled by alterations in the amino acid pattern of this tissue. 3. When protein concentration and protein synthesis were increased in skeletal muscle, protein concentration of small intestine was decreased, accompanied by elevated levels of amino acids in tissue. Protein synthesis of small intestine was not altered by the norleucine treatment. The results suggest a close interrelationship between skeletal muscle and small intestine with respect to protein turnover. 4. The effects of norleucine were less pronounced at 10 and 15 days of age, which indicates a metabolic adaptation to the treatment. 5. Alterations in amino acid concentrations of tissue due to changes in protein metabolism were not uniform but tissue-specific. 6. Current concepts for explaining the effects of branched-chain amino acids (BCAA) on protein turnover in skeletal muscle are based on the assumption that the BCAA or leucine alone might become rate-limiting for protein synthesis in muscle under catabolic conditions. The amino acid analogue norleucine, however, cannot replace any of the BCAA in protein. Additionally, norleucine affected protein metabolism in highly anabolic organisms. Therefore, the present thoughts on this issue appear to be incomplete.

scholarly journals Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

2021 ◽  
pp. 1-9
Author(s):  
Jorn Trommelen ◽  
Andrew M. Holwerda ◽  
Philippe J. M. Pinckaers ◽  
Luc J. C. van Loon
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Stable Isotope ◽  
Dietary Protein ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Human Subjects ◽  
Whole Body ◽  
Body Protein

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

scholarly journals 146 Prematurity Blunts the Protein Synthetic Response of Skeletal Muscle to Insulin and Amino Acids

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 118-119
Author(s):  
Teresa A Davis ◽  
Marko Rudar ◽  
Jane Naberhuis ◽  
Agus Suryawan ◽  
Marta Fiorotto
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Body Weight Gain ◽  
Human Infant ◽  
Long Term Effects ◽  
Plasma Insulin Concentration ◽  
Akt Phosphorylation ◽  
Relative Body Weight

Abstract Livestock animals are important dual-purpose models that benefit both agricultural and biomedical research. The neonatal pig is an appropriate model for the human infant to assess long-term effects of early life nutrition on growth and metabolic outcomes. Previously we have demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. The objective of this study was to determine whether reduced sensitivity to insulin and/or amino acids drives this blunted response. Pigs were delivered by caesarean section at preterm (PT, 103 d gestation) or at term (T, 112 d gestation) and fed parenterally for 4 d. On day 4, pigs were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps for 120 min, yielding six treatments: PT-FAST (n = 7), PT-INS (n = 9), PT-AA (n = 9), T-FAST (n = 8), T-INS (n = 9), and T-AA (n = 9). A flooding dose of L-[4-3H]Phe was injected into pigs 30 min before euthanasia. Birth weight and relative body weight gain were lower in PT than T pigs (P &lt; 0.001). Plasma insulin concentration was increased from ~3 to ~100 µU/mL in INS compared to FAST and AA pigs (P &lt; 0.001); plasma BCAA concentration was increased from ~250 to ~1,000 µmol/L in AA compared to FAST and INS pigs (P &lt; 0.001). Despite achieving similar insulin and amino acid levels, longissimus dorsi AKT phosphorylation, mechanistic target of rapamycin (mTOR)·Rheb abundance, mTOR activation, and protein synthesis were lower in PT-INS than T-INS pigs (Table 1). Although amino-acid induced dissociation of Sestrin2 from GATOR2 was not affected by prematurity, mTOR·RagA abundance, mTOR·RagC abundance, mTOR activation, and protein synthesis were lower in PT-AA than T-AA pigs. The impaired capacity of premature skeletal muscle to respond to insulin or amino acids and promote protein synthesis likely contributes to reduced lean mass accretion. Research was supported by NIH and USDA.

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