scholarly journals The inhibition of bacterial growth by hypochlorous acid. Possible role in the bactericidal activity of phagocytes

1988 ◽  
Vol 254 (3) ◽  
pp. 685-692 ◽  
Author(s):  
S M McKenna ◽  
K J A Davies
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Cell Division ◽  
Protein Degradation ◽  
Bacterial Growth ◽  
Colony Formation ◽  
Hypochlorous Acid ◽  
Selective Inhibition ◽  
Membrane Disruption ◽  
Bacterial Membrane

The ‘respiratory burst’ of phagocytes such as neutrophils generates superoxide which forms H2O2 by dismutation. H2O2 and Cl- ions serve as substrates for the enzyme myeloperoxidase to generate hypochlorous acid (HOCl). HOCl is thought to play an important role in bacterial killing, but its mechanism of action is not well characterized. Furthermore, although many studies in vitro have shown HOCl to be a damaging oxidant with little or no specificity (particularly at high concentrations), bacteria which have been ingested by phagocytes appear to experience a rapid and selective inhibition of cell division. Bacterial membrane disruption, protein degradation, and inhibition of protein synthesis, do not seem to occur in the early phases of phagocyte action. We have now found that low concentrations of HOCl exert a rapid and selective inhibition of bacterial growth and cell division, which can be blocked by taurine or amino acids. Only 20 microM-HOCl was required for 50% inhibition of bacterial growth (5 x 10(8) Escherichia coli/ml), and 50 microM-HOCl completely inhibited cell division (colony formation). These effects were apparent within 5 min of HOCl exposure, and were not reversed by extensive washings. DNA synthesis (incorporation of [3H]-thymidine) was significantly affected by even a 1 min exposure to 50 microM-HOCl, and decreased by as much as 96% after 5 min. In contrast, bacterial membrane disruption and extensive protein degradation/fragmentation (release of acid-soluble counts from [3H]leucine-labelled cells) were not observed at concentrations below 5 mM-HOCl. Protein synthesis (incorporation of [3H]leucine) was only inhibited by 10-30% following 5 min exposure to 50 microM-HOCl, although longer exposure produced more marked reductions (80% after 30 min). Neutrophils deficient in myeloperoxidase cannot convert H2O2 to HOCl, yet can kill bacteria. We have found that H2O2 is only 6% as effective as HOCl in inhibiting E. coli growth and cell division (0.34 mM-H2O2 required for 50% inhibition of colony formation), and taurine or amino acids do not block this effect. Our results are consistent with a rapid and selective inhibition of bacterial cell division by HOCl in phagocytes. H2O2 may substitute for HOCl in myeloperoxidase deficiency, but by a different mechanism and at a greater metabolic cost.

scholarly journals Effect of long-term refeeding on protein metabolism in patients with cirrhosis of the liver

1997 ◽  
Vol 77 (2) ◽  
pp. 197-212 ◽  
Author(s):  
Jens Kondrup ◽  
Klaus Nielsen ◽  
Anders Juul
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Protein Metabolism ◽  
Cirrhosis Of The Liver ◽  
N Balance ◽  
Whole Body ◽  
Protein Requirement ◽  
Protein Utilization ◽  
Igf I

Patients with cirrhosis of the liver require an increased amount of protein to achieve N balance. However, the utilization of protein with increased protein intake, i.e. the slope from regression analysis of N balance v. intake, is highly efficient (Nielsen et al. 1995). In the present study, protein requirement and protein utilization were investigated further by measuring protein synthesis and degradation. In two separate studies, five or six patients with cirrhosis of the liver were refed on a balanced diet for an average of 2 or 4 weeks. Protein and energy intakes were doubled in both studies. Initial and final whole-body protein metabolism was measured in the fed state by primed continous [15N]glycine infusion. Refeeding caused a statistically significant increase of about 30% in protein synthesis in both studies while protein degradation was only slightly affected. The increase in protein synthesis was associated with significant increases in plasma concentrations of total amino acids (25%), leucine (58%), isoleucine (82%), valine (72%), proline (48%) and triiodothyronine (27%) while insulin, growth hormone, insulin-like growth factor (IGF)-I and IGF-binding protein-3 were not changed significantly. The results indicate that the efficient protein utilization is due to increased protein synthesis, rather than decreased protein degradation, and suggest that increases in plasma amino acids may be responsible for the increased protein synthesis. A comparison of the patients who had a normal protein requirement with the patients who had an increased protein requirement suggests that the increased protein requirement is due to a primary increase in protein degradation. It is speculated that this is due to low levels of IGF-I secondary to impaired liver function, since initial plasma concentration of IGF-I was about 25% of control values and remained low during refeeding.

scholarly journals mTOR inhibition activates overall protein degradation by the ubiquitin proteasome system as well as by autophagy

2015 ◽  
Vol 112 (52) ◽  
pp. 15790-15797 ◽  
Author(s):  
Jinghui Zhao ◽  
Bo Zhai ◽  
Steven P. Gygi ◽  
Alfred Lewis Goldberg
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Mammalian Cells ◽  
Cholesterol Biosynthesis ◽  
Mammalian Target Of Rapamycin ◽  
Ubiquitin Proteasome System ◽  
Mtor Inhibition ◽  
Protein Ubiquitination ◽  
Ubiquitin Proteasome

Growth factors and nutrients enhance protein synthesis and suppress overall protein degradation by activating the protein kinase mammalian target of rapamycin (mTOR). Conversely, nutrient or serum deprivation inhibits mTOR and stimulates protein breakdown by inducing autophagy, which provides the starved cells with amino acids for protein synthesis and energy production. However, it is unclear whether proteolysis by the ubiquitin proteasome system (UPS), which catalyzes most protein degradation in mammalian cells, also increases when mTOR activity decreases. Here we show that inhibiting mTOR with rapamycin or Torin1 rapidly increases the degradation of long-lived cell proteins, but not short-lived ones, by stimulating proteolysis by proteasomes, in addition to autophagy. This enhanced proteasomal degradation required protein ubiquitination, and within 30 min after mTOR inhibition, the cellular content of K48-linked ubiquitinated proteins increased without any change in proteasome content or activity. This rapid increase in UPS-mediated proteolysis continued for many hours and resulted primarily from inhibition of mTORC1 (not mTORC2), but did not require new protein synthesis or key mTOR targets: S6Ks, 4E-BPs, or Ulks. These findings do not support the recent report that mTORC1 inhibition reduces proteolysis by suppressing proteasome expression [Zhang Y, et al. (2014) Nature 513(7518):440–443]. Several growth-related proteins were identified that were ubiquitinated and degraded more rapidly after mTOR inhibition, including HMG-CoA synthase, whose enhanced degradation probably limits cholesterol biosynthesis upon insulin deficiency. Thus, mTOR inhibition coordinately activates the UPS and autophagy, which provide essential amino acids and, together with the enhanced ubiquitination of anabolic proteins, help slow growth.

Selective Inhibition of Cleavage in Different Regions of the Frog Egg by Sulphydryl Inhibitors

Development ◽  
1956 ◽  
Vol 4 (1) ◽  
pp. 73-92
Author(s):  
Lucena J. Barth
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Total Nitrogen ◽  
Selective Inhibition ◽  
Inorganic Materials ◽  
Crescent Formation ◽  
Animal Pole ◽  
Grey Crescent ◽  
Histochemical Methods ◽  
Small Spot

That the materials for protein synthesis in the frog egg must come from yolk is indicated by the constancy of total nitrogen during development (Gregg & Ballentine, 1946) and the fact that the egg can develop with no outside source of organic or inorganic materials. When and where in the developing egg new proteins arise, and what are the mechanisms which control the rate and direct the specificity of such syntheses, are problems which are beginning to occupy increasing numbers investigators using several methods of attack—immunological, enzymological, electrophoretic, and incorporation of labelled amino acids, for example. Brachet (1940), using histochemical methods, described a change in the distribution of sulphydryl proteins coincident with grey crescent formation. In the newly-laid egg of Triton or Pleurodeles Brachet found the sulphydryl proteins to be restricted to a small spot centred about the maturation figure near the animal pole. This picture changed during the first few hours after fertilization.

scholarly journals Effects of amino acids, ammonia and leupeptin on protein synthesis and degradation in isolated rat hepatocytes

1978 ◽  
Vol 174 (2) ◽  
pp. 469-474 ◽  
Author(s):  
P O Seglen
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Specific Radioactivity ◽  
Rat Hepatocytes ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Isolated Rat Hepatocytes ◽  
Lysosomal Protein ◽  
Isolated Rat

Protein synthesis in isolated rat hepatocytes, as measured by the incorporation of [14C]-valine at constant specific radioactivity, proceeded at a rate of 0.3-0.5%/h in an unsupplemented medium, i.e. only about one-tenth the rate of protein degradation (4%/h). Leupeptin, which inhibits lysosomal protein degradation (previously found to be 75% of the total degradation in hepatocytes), had no effect on protein synthesis, showing that endogenous protein degradation supplied amino acids in excess of the substrate requirements for protein synthesis. The inhibition of protein synthesis by NH4Cl (another inhibitor of lysosomal protein degradation) as well as the stimulation by a physiological amino acid mixture must therefore represent indirect effects, either on general energy metabolism, or on unknown regulatory processes.

Regulation of protein synthesis and degradation during in vitro cardiac work

1980 ◽  
Vol 238 (5) ◽  
pp. E431-E442 ◽  
Author(s):  
H. E. Morgan ◽  
B. H. Chua ◽  
E. O. Fuller ◽  
D. Siehl
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Nitrogen Balance ◽  
Cardiac Work ◽  
Amino Acid Availability ◽  
Intracellular Concentrations ◽  
Substrate Mixtures ◽  
Beta Hydroxybutyrate

Cardiac work increased protein synthesis in hearts supplied glucose (mixture 1), glucose-insulin-glucagon-lactate-beta-hydroxybutyrate (mixture 2) or palmitate-beta-hydroxybutyrate-glucose (mixture 3). In hearts provided mixture 1, acceleration of synthesis involved increased rates of peptide chain initiation. In these hearts intracellular concentrations of 5 amino acids decreased and 13 others were unchanged, indicating that faster protein synthesis did not depend on increased amino acid availability. In hearts supplied mixtures 2, 3, or 4 (lactate-glucose-insulin), intracellular concentrations of branched-chain amino acids were decreased by work, whereas intracellular levels of some acidic and neutral amino acids increased. Protein degradation was decreased by work in hearts supplied mixtures 1 and 2, but not mixtures 3 and 4. In hearts provided mixture 1, nitrogen balance was negative, but less so in working preparations. Nitrogen balance was zero or positive in working hearts provided mixtures 2 and 4. These studies indicated that in hearts supplied some, but not all, of the substrate mixtures, cardiac work maintained efficiently of protein synthesis and inhibited protein degradation. An improved method for perfusion of working hearts with albumin-containing buffer is described.

Protein and amino acid metabolism in posterior hemicorpus of acutely uremic rats

1983 ◽  
Vol 244 (6) ◽  
pp. E615-E623 ◽  
Author(s):  
R. M. Flugel-Link ◽  
I. B. Salusky ◽  
M. R. Jones ◽  
J. D. Kopple
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Alkaline Protease ◽  
Cathepsin D ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Creatine Phosphate ◽  
Net Uptake ◽  
Nonessential Amino Acids

Protein synthesis and degradation and net uptake and release of amino acids and minerals were examined in the perfused hemicorpus of bilaterally nephrectomized and sham-operated control rats. Animals were studied 30 h after surgery. In comparison with controls, uremic rats had greater urea N appearance (net urea generation) and lower plasma and muscle concentrations of most amino acids. Muscle protein synthesis was not altered, but protein degradation was greater in uremic versus sham rats. There was greater net release of phenylalanine, tyrosine, alanine, total nonessential amino acids, total amino acids, potassium, and phosphorus from the perfused hemicorpus of uremic rats and greater release of citrulline from sham rats. ATP, creatine phosphate, cAMP, and activities of cathepsin B1, cathepsin D, and alkaline protease were not different in muscles of the uremic versus sham rats. Thus, in acutely uremic rats there is increased protein wasting in the hemicorpus due to enhanced protein degradation. The enhanced protein degradation does not appear to be due to increased muscle cathepsin B1, cathepsin D, or alkaline protease activities.

Protein Degradation in Human Skeletal Muscle Tissue: The Effect of Insulin, Leucine, Amino Acids and Ions

1981 ◽  
Vol 60 (3) ◽  
pp. 319-326 ◽  
Author(s):  
K. Lundholm ◽  
S. Edström ◽  
L. Ekman ◽  
I. Karlberg ◽  
P. Walker ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Muscle Tissue ◽  
Human Skeletal Muscle ◽  
Degradation Rate ◽  
Rectus Abdominus ◽  
Protein Degradation Rate

1. The protein degradation rate of human skeletal muscle was evaluated in vitro in isolated fibre bundles from the rectus abdominus muscle by measuring the tyrosine released from muscle tissue proteins. Protein metabolism in this semi-intact preparation was compared with that of the intact extensor digitorum longus muscles from rats under the same experimental conditions. 2. Protein balance was negative in both preparations, but protein synthesis and degradation were two to three times higher in the rat muscles. Tyrosine was released at a constant rate for at least 3 h of incubation independent of whether protein synthesis was inhibited or not. Disintegration of the muscle fibres more than doubled the tyrosine release rate. Human red gastrocnemius muscle showed 37% higher degradation rate compared with the predominantly white rectus abdominus muscle. The half-life of human skeletal muscle protein in vitro was estimated to be 20 days when calculated from the rate of tyrosine release. 3. The addition of leucine to the incubation medium decreased the rate of protein degradation, which was further decreased by the addition of other amino acids. Insulin did not influence the protein degradation rate during 2 h of incubation. This did not reflect a lack of sensitivity to insulin of the preparation, since protein synthesis responded to insulin. Calcium (5 mmol/l) stimulated and zinc (0.1 mmol/l) inhibited the protein degradation. 4. This experimental system may be suitable as an additional tool for evaluating protein degradation in human skeletal muscles.

Insulin selectively attenuates breakdown of nonmyofibrillar proteins in peripheral tissues of normal men

1994 ◽  
Vol 266 (4) ◽  
pp. E645-E652 ◽  
Author(s):  
A. C. Moller-Loswick ◽  
H. Zachrisson ◽  
A. Hyltander ◽  
U. Korner ◽  
D. E. Matthews ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Skeletal Muscles ◽  
Plasma Concentrations ◽  
Constant Infusion ◽  
Acid Uptake ◽  
Peripheral Tissues ◽  
Protein Pool ◽  
Glucose Clamp Technique

The role of insulin to control protein synthesis and degradation in the human leg and forearm was investigated in eight healthy individuals. The glucose clamp technique with simultaneous infusion of crystalline amino acids were used to create hyperinsulinemia (100–120 mU/l) in combination with euglycemia and elevated plasma concentrations of amino acids (> 4 mmol/l). A primed constant infusion with L-[U-14C]tyrosine and L-[phenyl-2H5]phenylalanine was used for simultaneous measurements of the disposal (protein synthesis) and the release (protein degradation) of tyrosine and phenylalanine, respectively, across the leg and forearm before and during hyperinsulinemia. The balance of 3-methylhistidine was also determined as a measure of muscle breakdown. Insulin stimulated tissue glucose and net amino acid uptake across the arm and leg tissues, whereas the disposal of both tyrosine and phenylalanine (protein synthesis) was not stimulated across the arm and the leg during hyperinsulinemia. The release of tyrosine and phenylalanine was significantly decreased from both leg and arm tissues (protein degradation) in response to insulin. However, the release of 3-methylhistidine from skeletal muscles was totally unaffected by hyperinsulinemia. We conclude that it is unlikely that insulin contributes to the normal stimulation of protein synthesis during feeding in humans and that insulin has no effect on breakdown of the large myofibrillar protein pool in skeletal muscles in unstressed individuals.

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