The amino acid composition of actin, myosin, tropomyosin and the meromyosins

Kominz, David R.; Hough, Aubrey J.; Symonds, P.; Laki, K.

doi:10.1016/0003-9861(54)90017-x

Cited by 225 publications

(56 citation statements)

References 17 publications

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“…The basal pattern of individual amino acids released from forearm muscle that we have observed agrees remarkably well with that described previously by London, Foley, and Webb (33). The high postabsorptive output of alanine relative to the other amino acids is striking since analysis of a wide variety of specific muscle proteins shows that alanine comprises no more than 10% of these proteins (34). Even after a 3-6 wk fast when the outputs of most amino acids including alanine have decreased, alanine release remains disproportionately high (35).…”

Section: * Probability That the Change In A-dv After Insulin Is A Chasupporting

confidence: 78%

Amino acid balance across tissues of the forearm in postabsorptive man. Effects of insulin at two dose levels

Pozefsky¹,

Felig²,

Tobin³

et al. 1969

J. Clin. Invest.

422

130

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A B S T R A C T Amino acid balance across skeletal muscle and across subcutaneous adipose tissue plus skin of the forearm has been quantified in postabsorptive man before and after insulin infusion into the brachial artery.Skeletal muscle released significant amounts of alpha amino nitrogen after an overnight fast. Most individual amino acids were released. Alanine output was by far the greatest. The pattern of release probably reflects both the composition of muscle protein undergoing degradation and de novo synthesis of alanine by transamination. A significant correlation was observed between the extent of release of each amino acid and its ambient arterial concentration.Elevation of forearm insulin in eight subjects from postabsorptive (12 uU/ml) to high physiologic levels (157 /IU/ml) in addition to stimulating muscle glucose uptake blocked muscle alpha amino nitrogen release by 74%. Consistent declines in output were seen for leucine, isoleucine, tyrosine, phenylalanine, threonine, glycine, and a-aminobutyric acid. Alanine output was insignificantly affected. Doubling forearm insulin levels (from 10 to 20 iAU/ml) in eight subjects increased muscle glucose uptake in three and blocked alpha amino nitrogen output in two although both effects were seen concurrently in only one subject. Changes in net amino acid balance after insulin could be accounted for by increased transport of amino acids into muscle cells or retardation of their exit.

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Section: * Probability That the Change In A-dv After Insulin Is A Chasupporting

confidence: 78%

Amino acid balance across tissues of the forearm in postabsorptive man. Effects of insulin at two dose levels

Pozefsky¹,

Felig²,

Tobin³

et al. 1969

J. Clin. Invest.

422

130

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“…In contrast, only transient splanchnic escape and peripheral uptake was observed for a variety of other amino acids. Inasmuch as the branched chain amino acids account for only 20% of the total amino acid residues in ingested beef (muscle) proteins (6,35), their primacy in protein-stimulated amino acid output from the splanchnic bed indicates a unique tendency for these amino acids to escape hepatic uptake and/or metabolism after intestinal absorption. A similar pattern of hepatic amino acid output involving the branched chain amino acids has been noted in a variety of experimental animals (dogs, rats, and sheep) after protein feeding (36)(37)(38).…”

Section: Resultsmentioning

confidence: 99%

“…It is thus clear that the branched chain amino acids are the major source for repletion of muscle nitrogen after protein intake. Furthermore, since the branched chain amino acids comprise only 20% of muscle amino acid residues (6,35) but are responsible for the majority of proteininduced amino acid uptake, it is likely that these amino acids are not solely utilized for protein synthesis but are largely catabolized in muscle. These data are in keeping with the conclusion that the branched amino acids are the major source of nitrogen for the glucosealanine cycle, (2,5,6,7,9) and possibly for muscle glutamine synthesis.…”

Section: Resultsmentioning

confidence: 99%

Effect of protein ingestion on splanchnic and leg metabolism in normal man and in patients with diabetes mellitus.

Wahren¹,

Felig²,

Hagenfeldt³

1976

J. Clin. Invest.

354

138

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A B S T R A C T The inter-organ flux of substrates after a protein-rich meal was studied in seven healthy subjects and in eight patients with diabetes mellitus. Arterial concentrations as well as leg and splanchnic exchange of amino acids, carbohydate substrates, free fatty acids (FFA), and ketone bodies were examined in the basal state and for 3 h after the ingestion of lean beef (3 g/kg body wt). Insulin was withheld for 24 h before the study in the diabetic patients.In the normal subjects, after protein ingestion, there was a large amino acid release from the splanchnic bed predominantly involving the branched chain amino acids. Valine, isoleucine, and leucine accounted together for more than half of total splanchnic amino acid output. Large increments were seen in the arterial concentrations of the branched chain amino acids (100-200%) and to a smaller extent for other amino acids. Leg exchange of most amino acids reverted from a basal net output to a net uptake after protein feeding which was most marked for the branched chain amino acids. The latter accounted for more than half of total peripheral amino acid uptake. Alanine and glutamine were continuously taken up by the splanchnic tissues and released by the leg tissues after the protein meal, although This work was presented in part at the 67th Annual

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“…Since alanine accounts for no more than 7-10% of the amino-acid residues in muscle proteins (16), peripheral synthesis of alanine by means of transamination of glucose-derived pyruvate has been suggested (8). Furthermore, on the basis of the large contribution of alanine to total hepatic amino-acid uptake (7) and its rapid conversion to glucose by perfused liver (17), a glucose-alanine cycle analogous to the Cori cycle for lactate has been proposed (8,9,17).…”

Section: Discussionmentioning

confidence: 99%

Evidence of Inter-organ Amino-Acid Transport by Blood Cells in Humans

Felig

Wahren²,

Räf

1973

Proc. Natl. Acad. Sci. U.S.A.

211

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To evaluate the contribution of blood cellular elements to inter-organ transport of amino acids, net exchange across the leg and splanchnic bed of 17 amino acids was determined in seven healthy postabsorptive subjects by use of both whole blood and plasma for analysis. Arterial-portal venous differences were measured in five additional subjects undergoing elective cholecystectomy. By use of whole blood, significant net release of amino acids was noted from the leg and gut, while a consistent uptake was observed by the splanchnic bed. The output of alanine from the leg and gut and the uptake of this amino acid by the splanchnic bed exceeded that of all other amino acids and accounted for 35-40% of total amino-acid exchange. Transport by way of plasma could not account for total tissue release or uptake of alanine, threonine, serine, glutamine, methionine, leucine, isoleucine, tyrosine, and citrulline. For each of these amino acids, significant tissue exchange was calculated to occur by way of the blood cellular elements, the direction of which generally paralleled the net shifts occurring in plasma. For alanine, 30% of its output from the leg and gut and 22% of its uptake by the splanchnic area occurred by way of blood cells. We conclude that the blood cellular elements, presumably erythrocytes, contribute substantially to the net flux of amino acids from muscle and gut to liver in normal postabsorptive humans. Alanine predominates in the inter-organ transfer of amino acids occurring by way of blood cells as well as plasma.It is generally believed that plasma rather than erythrocytes is the vehicle of amino-acid exchange between tissues (1). The slow equilibration time of amino-acid transport across erythrocyte membranes, as indicated by in vitro studies (2), has led to the widely held notion that erythrocytes are of little, if any, significance in the inter-organ transfer of amino acids. As a consequence, studies of amino-acid metabolism in physiologic as well as pathologic circumstances have generally been restricted to measurements of amino-acid concentrations in plasma rather than whole blood (1, 3). However, recent observations on glutamate flux in intact humans suggest a dynamic role for erythrocytes in the transport of this amino acid across muscle tissue (4). In addition, studies in dogs indicate that erythrocytes and plasma may play independent and occasionally opposing roles in the exchange of several amino acids across the liver and gut (5, 6). The present investigation was consequently undertaken to determine the contribution of blood cells, primarily erythrocytes, to inter-organ amino-acid transport in normal humans. This was done by examination of peripheral, splanchnic, and portal exchange of 17 individual amino acids in the postabsorptive state; whole blood as well as plasma was used for the determination of arterio-venous differences. In particular, we were interested in the contribution of the blood cellular elements to the tissue exchange of alanine. Plasma analyses have emphasized the ...

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The amino acid composition of actin, myosin, tropomyosin and the meromyosins

Cited by 225 publications

References 17 publications

Amino acid balance across tissues of the forearm in postabsorptive man. Effects of insulin at two dose levels

Amino acid balance across tissues of the forearm in postabsorptive man. Effects of insulin at two dose levels

Effect of protein ingestion on splanchnic and leg metabolism in normal man and in patients with diabetes mellitus.

Evidence of Inter-organ Amino-Acid Transport by Blood Cells in Humans

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