Topic
Phenylalanine
About: Phenylalanine is a research topic. Over the lifetime, 9829 publications have been published within this topic receiving 256009 citations. The topic is also known as: L-Phe & (S)-2-Amino-3-phenylpropionic acid.
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TL;DR: The main determinant of brain tryPTophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids that compete with it for uptake into the brain.
Abstract: When plasma tryptophan is elevated by the injection of tryptophan or insulin, or by the consumption of carbohydrates, brain tryptophan and serotonin also rise; however, when even larger elevations of plasma tryptophan are produced by the ingestion of protein-containing diets, brain tryptophan and serotonin do not change. The main determinant of brain tryptophan and serotonin concentrations does not appear to be plasma tryptophan alone, but the ratio of this amino acid to other plasma neutral amino acids (that is, tyrosine, phenylalanine, leucine, isoleucine, and valine) that compete with it for uptake into the brain.
1,090 citations
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TL;DR: It is found that pairs (dimers) of aromatic side chain amino acids preferentially align their respective aromatic rings in an off-centered parallel orientation, which is referred to as parallel displaced pi-stacking and is consistent with ab initio and molecular mechanics calculations of benzene dimer.
1,025 citations
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TL;DR: A rapid procedure for measuring the specific radioactivity of phenylalanine in tissues was developed, which facilitates the accurate determination of rates of protein synthesis in a wide range of tissues by injection of 150 mumol of L-[4-(3)H]phenylAlanine/100 g body wt.
Abstract: A rapid procedure for measuring the specific radioactivity of phenylalanine in tissues was developed. This facilitates the accurate determination of rates of protein synthesis in a wide range of tissues by injection of 150 mumol of L-[4-(3)H]phenylalanine/100 g body wt. The large dose of amino acid results in a rapid rise in specific radioactivity of free phenylalanine in tissues to values close to that in plasma, followed by a slow but linear fall. This enables the rate of protein synthesis to be calculated from measurements of the specific radioactivity of free and protein-bound phenylalanine in tissues during a 10 min period after injection of radioisotope.
903 citations
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TL;DR: It is concluded that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow, implying that protein intake immediately after exercise may be more anabolic than when ingested at some later time.
Abstract: Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.
823 citations
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TL;DR: Essential amino acids are primarily responsible for the amino acid-induced stimulation of muscle protein anabolism in the elderly.
778 citations