scholarly journals Protein turnover rates of two human subjects during an unassisted crossing of Antarctica

1996 ◽  
Vol 76 (2) ◽  
pp. 165-174 ◽  
Author(s):  
M. A. Stroud ◽  
A. A. Jackson ◽  
J. C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Human Subjects ◽  
Austral Summer ◽  
High Energy ◽  
Turnover Rates ◽  
Energy Expenditures ◽  
Combined Stresses ◽  
Freeze Dried ◽  
Product Method

During the Austral summer of 1992–3, two men, MS and RF, walked 2300 km across Antarctica in 96 d, unassisted by other men, animals or machines. During the journey they ate freeze-dried rations, towed on sledges, that contained an average of 21·3 MJ/d of which 56·7% was fat, 35·5% carbohydrate and 7·8% protein (98·8 g). Despite this high energy intake both men lost more than 20 kg in body weight due to their extremely high energy expenditures. Studies of protein turnover using [15N]glycine by the single-dose end-product method were made before, during and after the journey, and these demonstrated considerable differences in the metabolic responses of the two men to the combined stresses of exercise, cold and undernutrition. However, both men maintained high and relatively stable levels of protein synthesis during the expedition despite the great exertion and the onset of considerable debilitation. This stability indicates the vital physiological function of protein synthesis.

scholarly journals The end-product method of measuring whole-body protein turnover: a review of published results and a comparison with those obtained by leucine infusion

2005 ◽  
Vol 94 (2) ◽  
pp. 141-153 ◽  
Author(s):  
S. L. Duggleby ◽  
J. C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Gold Standard ◽  
Protein Turnover ◽  
Population Studies ◽  
Whole Body ◽  
Precursor Method ◽  
Body Protein ◽  
Short Account ◽  
Product Method ◽  
Pros And Cons

The present review summarizes the results of all published papers on whole-body protein turnover in man measured by [15N]glycine and the end-product method using both urea and ammonia. It begins with a short account of the underlying assumptions and the justification for the use of [15N]glycine. The results are then compared with those of a large sample of measurements by the ‘gold standard’ precursor method with continuous infusion of [13C]leucine. The pros and cons of the two methods are compared and it is suggested that there is a place for further work by the less invasive end-product method, particularly for population studies of the genetic, environmental and functional determinants of whole-body rates of protein synthesis.

scholarly journals Proteome dynamics during homeostatic scaling in cultured neurons

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Aline Ricarda Dörrbaum ◽  
Beatriz Alvarez-Castelao ◽  
Belquis Nassim-Assir ◽  
Julian D Langer ◽  
Erin M Schuman
Keyword(s):  
Protein Synthesis ◽  
Protein Function ◽  
Protein Turnover ◽  
Experimental Approach ◽  
Large Fraction ◽  
Synaptic Proteins ◽  
Turnover Rates ◽  
Cellular Environment ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Protein turnover, the net result of protein synthesis and degradation, enables cells to remodel their proteomes in response to internal and external cues. Previously, we analyzed protein turnover rates in cultured brain cells under basal neuronal activity and found that protein turnover is influenced by subcellular localization, protein function, complex association, cell type of origin, and by the cellular environment (Dörrbaum et al., 2018). Here, we advanced our experimental approach to quantify changes in protein synthesis and degradation, as well as the resulting changes in protein turnover or abundance in rat primary hippocampal cultures during homeostatic scaling. Our data demonstrate that a large fraction of the neuronal proteome shows changes in protein synthesis and/or degradation during homeostatic up- and down-scaling. More than half of the quantified synaptic proteins were regulated, including pre- as well as postsynaptic proteins with diverse molecular functions.

scholarly journals The number of catalytic cycles in an enzyme’s lifetime and why it matters to metabolic engineering

2021 ◽  
Vol 118 (13) ◽  
pp. e2023348118
Author(s):  
Andrew D. Hanson ◽  
Donald R. McCarty ◽  
Christopher S. Henry ◽  
Xiaochen Xian ◽  
Jaya Joshi ◽  
...  
Keyword(s):  
Metabolic Engineering ◽  
Active Site ◽  
Protein Turnover ◽  
Metabolic Flux ◽  
Failure Modes ◽  
High Energy ◽  
Enzyme Engineering ◽  
Turnover Rates ◽  
Catalytic Cycles

Metabolic engineering uses enzymes as parts to build biosystems for specified tasks. Although a part’s working life and failure modes are key engineering performance indicators, this is not yet so in metabolic engineering because it is not known how long enzymes remain functional in vivo or whether cumulative deterioration (wear-out), sudden random failure, or other causes drive replacement. Consequently, enzymes cannot be engineered to extend life and cut the high energy costs of replacement. Guided by catalyst engineering, we adopted catalytic cycles until replacement (CCR) as a metric for enzyme functional life span in vivo. CCR is the number of catalytic cycles that an enzyme mediates in vivo before failure or replacement, i.e., metabolic flux rate/protein turnover rate. We used estimated fluxes and measured protein turnover rates to calculate CCRs for ∼100–200 enzymes each from Lactococcus lactis, yeast, and Arabidopsis. CCRs in these organisms had similar ranges (<103 to >107) but different median values (3–4 × 104 in L. lactis and yeast versus 4 × 105 in Arabidopsis). In all organisms, enzymes whose substrates, products, or mechanisms can attack reactive amino acid residues had significantly lower median CCR values than other enzymes. Taken with literature on mechanism-based inactivation, the latter finding supports the proposal that 1) random active-site damage by reaction chemistry is an important cause of enzyme failure, and 2) reactive noncatalytic residues in the active-site region are likely contributors to damage susceptibility. Enzyme engineering to raise CCRs and lower replacement costs may thus be both beneficial and feasible.

scholarly journals Protein turnover in the developing Triticum aestivum grain

2021 ◽  
Author(s):  
Hui Cao ◽  
Owen Duncan ◽  
A. Harvey Millar
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Storage Proteins ◽  
Spatiotemporal Pattern ◽  
Turnover Rates ◽  
Grain Development ◽  
Wheat Grain ◽  
Stable Isotope Labelling ◽  
Atp Production

Protein abundance in cereal grains is determined by the relative rates of protein synthesis and protein degradation during grain development. Through combining in vivo stable isotope labelling and in-depth quantitative proteomics, we have measured the turnover of 1400 different types of proteins during wheat grain development. We demonstrate that there is a spatiotemporal pattern to protein turnover rates which explain part of the variation in protein abundances that is not attributable to differences in wheat gene expression. We show that approximately 20% of total grain ATP production is used for grain proteome biogenesis and maintenance, and nearly half of this budget is invested exclusively in storage protein synthesis. We calculate that 25% of newly synthesized storage proteins are turned over during grain development rather than stored. This approach to measure protein turnover rates at proteome scale reveals how different functional categories of grain proteins accumulate, calculates the costs of protein turnover during wheat grain development and identifies the most and the least stable proteins in the developing wheat grain.

scholarly journals Protein turnover and growth in the whole body, liver and kidney of the rat from the foetus to senility

1984 ◽  
Vol 217 (2) ◽  
pp. 507-516 ◽  
Author(s):  
D F Goldspink ◽  
F J Kelly
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Post Partum ◽  
Protein Composition ◽  
Whole Body ◽  
Turnover Rates ◽  
Tissue Mass ◽  
Age Related ◽  
Foetal Life

Changes in the growth and protein turnover (measured in vivo) of the rat liver, kidney and whole body were studied between 16 days of life in utero and 105 weeks post partum. Tissue and whole-body growth were related to changes in both cellular hyperplasia (i.e. changes in DNA) and hypertrophy (protein/DNA values) and to the protein composition within the enlarging tissue mass. The suitability of using a single large dose of phenylalanine for measuring the rates of protein synthesis during both pre- and post-natal life was established. The declining growth rates in the whole animal and the two visceral tissues were then explained by developmental changes in the fractional rates of protein synthesis and breakdown, turnover rates being age-for-age higher in the liver than in the kidney, which in turn were higher than those measured in the whole animal. The declining fractional rates of synthesis in both tissues and the whole body with increasing age were related to changes in the tissues' ribosomal capacity and activity. The fall in the hepatic rate between 18 and 20 days of foetal life (from 134 to 98% per day) corresponded to a decrease in both the ribosomal capacity and the rate of synthesis per ribosome. No significant changes in any of these parameters were, however, found in the liver between weaning (3 weeks) and senility (105 weeks). In contrast, the fractional synthetic (and degradative) rates progressively declined in the kidney (from 95 to 24% per day) and whole body (from 70 to 11% per day) throughout both pre- and post-natal life, mainly as a consequence of a progressive decline in the ribosomal capacity, but with some fall in the ribosomal activity also during foetal life. The age-related contributions of these visceral tissues to the total amount of protein synthesized per day by the whole animal were determined. The renal contribution remained fairly constant at 1.6-2.9%, whereas the hepatic contribution declined from 56 to 11%, with increasing age. Approximate-steady-state conditions were reached at, and between, 44 and 105 weeks post partum, the half-life values of mixed whole-body, kidney and liver proteins being 6.4, 3.0 and 1.5 days, respectively, at 105 weeks.

scholarly journals Protein turnover forms one of the highest maintenance costs in Lactococcus lactis

Microbiology ◽  
2014 ◽  
Vol 160 (7) ◽  
pp. 1501-1512 ◽  
Author(s):  
Petri-Jaan Lahtvee ◽  
Andrus Seiman ◽  
Liisa Arike ◽  
Kaarel Adamberg ◽  
Raivo Vilu
Keyword(s):  
Growth Rate ◽  
Total Energy ◽  
Specific Growth Rate ◽  
Lactococcus Lactis ◽  
Protein Turnover ◽  
Biomass Yield ◽  
Specific Growth ◽  
High Energy ◽  
Turnover Rates ◽  
Maintenance Costs

Protein turnover plays an important role in cell metabolism by regulating metabolic fluxes. Furthermore, the energy costs for protein turnover have been estimated to account for up to a third of the total energy production during cell replication and hence may represent a major limiting factor in achieving either higher biomass or production yields. This work aimed to measure the specific growth rate (μ)-dependent abundance and turnover rate of individual proteins, estimate the ATP cost for protein production and turnover, and compare this with the total energy balance and other maintenance costs. The lactic acid bacteria model organism Lactococcus lactis was used to measure protein turnover rates at μ = 0.1 and 0.5 h−1 in chemostat experiments. Individual turnover rates were measured for ~75 % of the total proteome. On average, protein turnover increased by sevenfold with a fivefold increase in growth rate, whilst biomass yield increased by 35 %. The median turnover rates found were higher than the specific growth rate of the bacterium, which suggests relatively high energy consumption for protein turnover. We found that protein turnover costs alone account for 38 and 47 % of the total energy produced at μ = 0.1 and 0.5 h−1, respectively, and gene ontology groups Energy metabolism and Translation dominated synthesis costs at both growth rates studied. These results reflect the complexity of metabolic changes that occur in response to changes in environmental conditions, and signify the trade-off between biomass yield and the need to produce ATP for maintenance processes.

Respiratory energy requirements and rate of protein turnover in vivo determined by the use of an inhibitor of protein synthesis and a probe to assess its effect

1994 ◽  
Vol 92 (4) ◽  
pp. 585-594 ◽  
Author(s):  
T. J. Bouma ◽  
R. De Visser ◽  
J. H. J. A. Janssen ◽  
M. J. De Kock ◽  
P H. Van Leeuwen ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Energy Requirements ◽  
Inhibitor Of Protein Synthesis

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats

2000 ◽  
Vol 278 (3) ◽  
pp. R705-R711 ◽  
Author(s):  
T. A. McAllister ◽  
J. R. Thompson ◽  
S. E. Samuels
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Cold Acclimation ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Turnover ◽  
Protein Mass ◽  
The Absolute

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C (cold) or 25°C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was ∼28% lower in skeletal muscle (gastrocnemius and soleus) and ∼24% higher in heart in cold compared with control rats ( P < 0.05). In skeletal muscle, the fractional rates of protein synthesis ( k syn) and degradation ( k deg) were not significantly different between cold and control rats, although k syn was lower (approximately −26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately −21%; P < 0.05) and degradation (approximately −13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k syn(approximately +12%; P < 0.1) and k deg(approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats ( P < 0.05). Plasma triiodothyronine concentration was higher ( P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

scholarly journals Influence of Subcellular Localization and Functional State on Protein Turnover

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1747
Author(s):  
Roya Yousefi ◽  
Kristina Jevdokimenko ◽  
Verena Kluever ◽  
David Pacheu-Grau ◽  
Eugenio F. Fornasiero
Keyword(s):  
Subcellular Localization ◽  
Functional State ◽  
Protein Turnover ◽  
Protein Localization ◽  
Small Gtpase ◽  
Turnover Rates ◽  
Cellular Behavior ◽  
Two Factors ◽  
Brain Creatine Kinase ◽  
Selection Of

Protein homeostasis is an equilibrium of paramount importance that maintains cellular performance by preserving an efficient proteome. This equilibrium avoids the accumulation of potentially toxic proteins, which could lead to cellular stress and death. While the regulators of proteostasis are the machineries controlling protein production, folding and degradation, several other factors can influence this process. Here, we have considered two factors influencing protein turnover: the subcellular localization of a protein and its functional state. For this purpose, we used an imaging approach based on the pulse-labeling of 17 representative SNAP-tag constructs for measuring protein lifetimes. With this approach, we obtained precise measurements of protein turnover rates in several subcellular compartments. We also tested a selection of mutants modulating the function of three extensively studied proteins, the Ca2+ sensor calmodulin, the small GTPase Rab5a and the brain creatine kinase (CKB). Finally, we followed up on the increased lifetime observed for the constitutively active Rab5a (Q79L), and we found that its stabilization correlates with enlarged endosomes and increased interaction with membranes. Overall, our data reveal that both changes in protein localization and functional state are key modulators of protein turnover, and protein lifetime fluctuations can be considered to infer changes in cellular behavior.

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.

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