Muscle protein degradation and amino acid metabolism during prolonged knee-extensor exercise in humans

1999 ◽  
Vol 97 (5) ◽  
pp. 557-567 ◽  
Author(s):  
G. VAN HALL ◽  
B. SALTIN ◽  
A. J. M. WAGENMAKERS
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Degradation ◽  
Acid Production ◽  
Glycogen Content ◽  
Muscle Protein ◽  
Knee Extensor ◽  
Total Amino Acid ◽  
Amino Acid Production ◽  
Muscle Protein Degradation

The aim of this study was to investigate whether prolonged one-leg knee-extensor exercise enhances net protein degradation in muscle with a normal or low glycogen content. Net amino acid production, as a measure of net protein degradation, was estimated from leg exchange and from changes in the concentrations of amino acids that are not metabolized in skeletal muscle. Experiments were performed at rest and during one-leg knee-extensor exercise in six subjects having one leg with a normal glycogen content and the other with a low glycogen content. Exercise was performed for 90 min at a workload of 60–65% of maximal one-leg power output, starting either with the normal-glycogen or the low-glycogen leg, at random. The net production of threonine, lysine and tyrosine and the sum of the non-metabolized amino acids were 9–20-fold higher (P< 0.05) during exercise of the normal-glycogen leg than at rest. Total amino acid production was also 10-fold higher during exercise compared with that at rest (difference not significant). The net production rates of threonine, glycine and tyrosine and of the sum of the non-metabolized amino acids were about 1.5–2.5-fold higher during exercise with the leg with a low glycogen content compared with the leg with a normal glycogen content (P< 0.05). Total amino acid production was 1.5-fold higher during exercise for the low-glycogen leg compared with the normal-glycogen leg (difference not significant). These data indicate that prolonged one-leg knee-extensor exercise leads to a substantial increase in net muscle protein degradation, and that a lowering of the starting muscle glycogen content leads to a further increase. The carbon atoms of the branched-chain amino acids (BCAA), glutamate, aspartate and asparagine, liberated by protein degradation, and the BCAA and glutamate extracted in increased amounts from the blood during exercise, are used for the synthesis of glutamine and for tricarboxylic-acid cycle anaplerosis.

Influence of fatty acids on ammonia and amino acid flux from active human muscle

1991 ◽  
Vol 261 (2) ◽  
pp. E168-E176 ◽  
Author(s):  
T. E. Graham ◽  
B. Kiens ◽  
M. Hargreaves ◽  
E. A. Richter
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Muscle Protein ◽  
Knee Extensor ◽  
Essential Amino Acids ◽  
Order Effect ◽  
Work Capacity ◽  
Human Muscle ◽  
Control Series ◽  
Ammonia Release

This study examined the dynamics of ammonia and amino acid exchange of human muscle during prolonged steady-state one-legged exercise at 80% of knee extensor maximal work capacity. Subjects (n = 10) performed leg extensor exercise for 1 h (control series), rested for 40 min while an infusion of Intralipid and heparin was begun, and then exercised the contralateral leg with the identical protocol [free fatty acid (FFA) series]. In the control series, ammonia efflux rose progressively, and 4.4 +/- 0.6 mmol were released in 1 h compared with 2.4 +/- 0.5 mmol (P less than 0.05) in the FFA series. The exercise was associated with large effluxes of total amino acids from the active muscle over the hour (12.8 +/- 4.3 and 10.3 +/- 3.3 mmol for control and FFA, respectively). Glutamine and alanine accounted for 47 and 64% of the efflux for the control and FFA series, respectively, while comparable values for essential amino acids were 24 and 20%. The latter implies that a net muscle protein catabolism was occurring during the exercise. The FFA treatment was associated not only with a reduced muscle ammonia release but also with a decreased (P less than 0.05) arterial concentration of nine amino acids (alanine, methionine, lysine, hydroxyproline, serine, glycine, proline, asparagine, and ornithine). Interpretation is limited due to the treatment order effect, but these data are compatible with the hypothesis that plasma clearance was affected by FFA.

scholarly journals Rates of protein synthesis in skin and bone, and their importance in the assessment of protein degradation in the perfused rat hemicorpus

1981 ◽  
Vol 194 (1) ◽  
pp. 373-376 ◽  
Author(s):  
V R Preedy ◽  
P J Garlick
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Degradation ◽  
Muscle Tissue ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Muscle Protein ◽  
Muscle Metabolism ◽  
Muscle Protein Degradation

The perfused rat hemicorpus preparation, which has frequently been used to study muscle metabolism, contains 39% by weight of non-muscle tissue such as skin and bone. Both the concentration of RNA and the incorporation of [U-14C]tyrosine into protein indicate that the non-muscle components are more active in protein synthesis than is muscle. These observations have important implications for studies of amino acid metabolism, and in particular for the measurement of muscle protein degradation in the hemicorpus.

scholarly journals Genome Sequence of Leuconostoc mesenteroides LK-151 Isolated from a Japanese Sake Cellar as a High Producer of d-Amino Acids

2017 ◽  
Vol 5 (30) ◽  
Author(s):  
Shiro Kato ◽  
Tadao Oikawa
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Acid Production ◽  
Leuconostoc Mesenteroides ◽  
Amino Acid Production ◽  
Content Type

ABSTRACT Here, we report the complete genome sequence of strain LK-151 of Leuconostoc mesenteroides, which was isolated from a Japanese sake cellar and has the potential to produce large amounts of d-amino acids, namely, d-Ala and d-Glu. The genome contains 4 genes related to d-amino acid production.

scholarly journals The localization of proteolytic activity in rat liver mitochondria and its relation to mitochondrial swelling and aging

1969 ◽  
Vol 111 (5) ◽  
pp. 763-776 ◽  
Author(s):  
K. G. M. M. Alberti ◽  
W. Bartley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Proteolytic Activity ◽  
Rat Liver ◽  
Acid Production ◽  
Liver Mitochondria ◽  
Ground Substance ◽  
Rat Liver Mitochondria ◽  
Amino Acid Production ◽  
Freezing And Thawing

1. On storage of rat liver mitochondria at 0°, water content, total amino acid content and leakage of protein all rose steadily over a 72hr. period. The initial ratio of intramitochondrial to extramitochondrial amino acid concentration lay between 18 and 24. Initially this rose, but it then fell to 1·9 at the end of storage. The concentration gradient between internal and external amino acids was relatively constant throughout the period. These processes were accentuated at 22° and 40°, the concentration gradient reaching 70μmoles/ml., water content rising to 8·3mg./mg. dry wt. and protein leakage reaching 42% of total mitochondrial protein. ‘Swelling agents’ produced no correlated changes in amino acid production and swelling. 2. Added glutamate was not concentrated within the pellet of whole or disrupted mitochondria. Endogenous amino acids were distributed evenly between the pellet and the supernatant of disrupted mitochondria. It is concluded that amino acids are produced within mitochondria and that adsorption and uptake from the medium do not contribute significantly to amino acids in the pellet. 3. β-Glycerophosphate, a lysosome protectant, increased amino acid production by rat liver mitochondria. Treatment with Triton X-100 and disruption by freezing and thawing showed that 56% of proteolytic activity was ‘free’ in whole mitochondria, whereas only 11% of acid phosphatase activity, a lysosomal enzyme, was ‘free’. 4. ‘Light’ mitochondria contained 30% more neutral proteolytic activity but 300% more acid phosphatase activity than ‘heavy’ mitochondria. 5. Electron micrographs of mitochondrial preparations showed less than one particle in 500 that could be identified as a lysosome. Treatment with Triton X-100 disrupted the structure of roughly 50% of the mitochondria; the rest appeared to retain their membrane, cristae and ground substance. Freezing and thawing caused gross swelling and loss of ground substance and rupture of external membranes. 6. Of the recovered proteolytic activity, 81% at pH7·4 and 70% at pH5·8 were found in the high-speed supernatant of broken mitochondria. A further fivefold increase in specific activity was found in the first protein fraction obtained by Sephadex G-50 gel filtration. 7. Between 60 and 80% of proteolytic activity was found in the 40–60%-saturated ammonium sulphate precipitate. Almost all of the soluble-fraction proteolytic activity could be recovered in a pH5·0 supernatant. 8. The results give no support to the view that mitochondrial neutral proteolytic activity reflects lysosomal content. 9. The possible role of intramitochondrial amino acid production and the proteolysis of internal barriers in passive swelling of mitochondria is discussed.

scholarly journals Inverse Regulation of Protein Turnover and Amino Acid Transport in Skeletal Muscle of Hypercatabolic Patients

2002 ◽  
Vol 87 (7) ◽  
pp. 3378-3384 ◽  
Author(s):  
Gianni Biolo ◽  
R. Y. Declan Fleming ◽  
Sergio P. Maggi ◽  
Thuan T. Nguyen ◽  
David N. Herndon ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Degradation ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Transmembrane Transport ◽  
Protein Breakdown ◽  
Balance Technique

We have investigated the relationships between the rates of muscle protein synthesis and degradation and of transmembrane transport of selected amino acids in leg skeletal muscle of 19 severely burned patients and 18 normal controls in the postabsorptive state. Patients were studied on the 14 ± 5 postburn day, and their mean burn size was 66% ± 18% of total body surface area. Methods were based on the leg arteriovenous balance technique in combination with biopsies of the vastus lateralis muscle and infusions of isotopic tracers of amino acids. Net muscle protein breakdown was greater in the patients because of an 83% increase in the rate of muscle protein degradation. The rate of muscle protein synthesis was also increased in the patients but to a lesser extent than protein degradation, i.e. by 50% with the arteriovenous phenylalanine balance technique and by 49% with the direct tracer incorporation method. The absolute values of inward transport of phenylalanine, leucine, and lysine were not significantly different in the two groups. However, the ability of transport systems to take up amino acids from the bloodstream, as assessed by dividing inward transport by amino acid delivery to leg muscle, were 50–63% lower in the patients. In contrast, outward phenylalanine and lysine transport were 40% and 67% greater in the patients than in the controls, respectively. We conclude the primary alteration in muscle protein metabolism is an acceleration of protein breakdown, and the increase in protein synthesis likely is due to increased intracellular amino acid availability as a result of accelerated breakdown. Transmembrane transport in the outward direction is accelerated, presumably to facilitate the export of amino acids from muscle to other tissues. In contrast, transmembrane transport in the inward direction is impaired relatively to the increased delivery of circulating amino acid to skeletal muscle secondary to accelerated blood flow.

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