scholarly journals The role of phosphoenolpyruvate carboxykinase in amino acid metabolism in muscle

1978 ◽  
Vol 176 (2) ◽  
pp. 623-626 ◽  
Author(s):  
E A Newsholme ◽  
T Williams
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Malate Dehydrogenase ◽  
Amino Acid Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Acid Metabolism ◽  
High Protein Diet ◽  
High Protein ◽  
Protein Diet

Starvation or feeding rats on a high-protein diet, valine or isoleucine, but not leucine, increases the activity of muscle phosphoenolpyruvate carboxykinase, but has no effect on NADP+-linked malate dehydrogenase. This suggests that muscle phosphoenolpyruvate carboxykinase is involved in oxidation or conversion of some amino acids to alanine.

scholarly journals Characterization of homocysteine metabolism in the rat liver

2000 ◽  
Vol 350 (3) ◽  
pp. 685-692 ◽  
Author(s):  
Lori M. STEAD ◽  
Margaret E. BROSNAN ◽  
John T. BROSNAN
Keyword(s):  
Amino Acid ◽  
Dietary Protein ◽  
High Protein Diet ◽  
Plasma Homocysteine ◽  
High Protein ◽  
Protein Diet ◽  
Total Plasma ◽  
Methionine Concentration ◽  
Protein Group

Recent evidence suggests that an increased plasma concentration of the sulphur amino acid homocysteine is a risk factor for the development of vascular disease. The tissue(s) responsible for homocysteine production and export to the plasma are not well known. However, given the central role of the liver in amino acid metabolism, we developed a rat primary hepatocyte model in which homocysteine (and cysteine) production and export were examined. The dependence of homocysteine export from incubated hepatocytes on methionine concentration fitted well to a rectangular hyperbola, with half-maximal homocysteine export achieved at methionine concentrations of approx. 0.44mM. Hepatocytes incubated with 1mM methionine and 1mM serine (a substrate for the transulphuration pathway of homocysteine removal) produced and exported significantly less homocysteine (25–40%) compared with cells incubated with 1mM methionine alone. The effects of dietary protein on homocysteine metabolism were also examined. Rats fed a 60% protein diet had a significantly increased total plasma homocysteine level compared with rats fed a 20% protein diet. Invitro effects of dietary protein were examined using hepatocytes isolated from animals maintained on these diets. When incubated with 1mM methionine, hepatocytes from rats fed the high protein diet exported significantly more homocysteine compared with hepatocytes from rats fed the normal protein diet. Inclusion of serine significantly lowered homocysteine export in the normal protein group, but the effect was more marked in the high protein group. Invivo effects of serine were also examined. Rats fed a high protein diet enriched with serine had significantly lower total plasma homocysteine (25–30%) compared with controls. These data indicate a significant role for the liver in the regulation of plasma homocysteine levels.

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

Fluxes and membrane transport of amino acids in rat liver under different protein diets

1990 ◽  
Vol 259 (5) ◽  
pp. E614-E625 ◽  
Author(s):  
P. Fafournoux ◽  
C. Remesy ◽  
C. Demigne
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aromatic Amino Acids ◽  
High Protein Diet ◽  
High Protein ◽  
Protein Diet ◽  
Transport Systems ◽  
Low Concentrations ◽  
Significant Uptake

The aim of the present work was to evaluate in vivo the role of the transport step in hepatic amino acid metabolism. To vary hepatic utilization of amino acids, rats were adapted to diets containing various concentrations of casein (5, 15, and 60%). In rats fed 5 or 15% casein diets, Gln and Glu were released by the liver, and there was a significant uptake of Ala. Hepatic fluxes of amino acids increased considerably after adaptation to high-casein diet (up to 1.55 mumol.min-1.g liver-1 for Ala), because of the rise in afferent concentrations as well as enhanced uptake percentage (peaking at 60–75% for most glucogenic amino acids). Adaptation to a high-protein diet led to induction of not only system A but also of most of the other transport systems (Gly, anionic, T, y+, and to a lesser extent system N); only systems ASC and L were unchanged. The study of amino acid repartition between liver and plasma with different diets indicates that transport could modulate utilization of Ala, Ser, Thr, Gly, Gln, and Asp. For Arg and Asn, present in very low concentrations in liver under any condition, the transport step should be the major locus of control of their metabolism. For amino acids chiefly transported by nonconcentrative systems, such as aromatic amino acids, cellular metabolism could also be limited by the transport process. In conclusion, during adaptation to a high-protein diet, there is apparently a coordinated adaptation of amino acid transport and of their intracellular metabolism. For some amino acids, induction of catabolic enzymes seems greater than that of transport, so that the transport step may play an important role in control of metabolic fluxes. For example, concentration of amino acids such as Thr may be markedly depressed in rats adapted to a high-protein diet.

scholarly journals Exchange (uptake and synthesis) of amino acids in the digestive tract of cattle when used in diet different ingredient composition of the feed

2019 ◽  
pp. 54-57
Author(s):  
Sviatoslav Valerievich Lebedev ◽  
Elmira Zakievna Gubaidulina ◽  
Elena Vladimirovna Sheida ◽  
Victoria Vladimirovna Grechkina
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Digestive Tract ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Fish Meal ◽  
Sunflower Meal ◽  
Basic Amino Acids ◽  
Ingredient Composition

Materials characterizing the role of digestive tract in amino acid metabolism are obtained based on studies assessing the effect of diets with various sources of protein (fish meal, sunflower meal). A number of metabolic regularities (synthesis and assimilation) of amino acids in the digestive tract of an animal follow from the data obtained by us. Сhyme inflowing from the stomach into intestine, contains 1.5-2 times more amino acids, compared with the number of them in the diet. Consequently, the same amount of basic amino acids can be synthesized in the process of digestion of ruminants. Most of amino acids from chyme is digested in the intestine. The actual amount of amino acids digested and included in the metabolism of animal was significantly higher than their content in the eaten dietand reached 108.1 - 148.9% of that received with the diet.

Excretion of Taurine during Healing of Experimental Wounds

1960 ◽  
Vol 6 (2) ◽  
pp. 140-147 ◽  
Author(s):  
Martin B Williamson ◽  
John M Passmann
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Total Nitrogen ◽  
High Protein Diet ◽  
High Protein ◽  
Protein Diet ◽  
Nitrogen Excretion ◽  
Amino Acid Nitrogen ◽  
Protein Free Diet

Abstract A comparison of the excretion of amino acids by normal and wounded rats on a high protein and protein-free diet was made. The nontaurine amino acid nitrogen excretion was found to be the same the control and wounded animals, although the rats on the high protein diet excreted considerably more amino acid nitrogen than did those on the protein-free diet. The wounded animals on the high protein diet had the same total nitrogen output but excreted significantly larger amounts of taurine than did the nonwounded controls. The wounded animals given the protein-free diet excreted the same amount of taurine but produced more total nitrogen than did the control rats. On the basis of the total nitrogen-taurine excretion ratios, data indicate that cystine is conserved by the wounded as compared to the normal animals.

The acute transient polymorphic psychosis: a biochemical subtype of the cycloid psychosis

2003 ◽  
Vol 15 (1) ◽  
pp. 38-43 ◽  
Author(s):  
L Pepplinkhuizen ◽  
F M M A van der Heijden ◽  
S Tuinier ◽  
W M A Verhoeven ◽  
D Fekkes
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Psychotic Disorders ◽  
Acid Metabolism ◽  
Plasma Concentrations ◽  
One Carbon Metabolism ◽  
The One

Background:The pathogenesis of atypical psychoses, in particularly those characterized by polymorphic psychopathology, is hypothesized to be related to disturbances in amino acid metabolism.Objective:In the present study, the role of the amino acid serine was investigated in patients with acute transient polymorphic psychosis.Methods:Patients were loaded with serine and with the amino acids glycine and alanine as controls and subsequently evaluated for the development of psychopathological symptoms. In addition, plasma levels of amino acids were measured.Results:In a subgroup of patients suffering from atypical psychoses, this biochemical challenge resulted in the reappearance of psychedelic symptoms in particular. Furthermore, significantly lower plasma concentrations of serine were found. In vitro experiments revealed a disturbance in the one-carbon metabolism. In another group of patients the loading provoked vegetative symptoms and fatigue.Conclusions:Disturbances in amino acid metabolism may be involved in the emergence of certain psychotic disorders.

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