Amino acids concentrations in humans

Palmer A. M., Marion D. W., Botscheller M. L., Bowen D. M., and DeKosky S. T. (1994) Increased transmitter amino acid concentration in human ventricular CSF after brain trauma. NeuroReport 6, 153-156. 

Mcmenemy, R. M., Lund, C. C., and Oncley, J. L., Unbound amino acid concentrations in human blood plasmas, /. Clin. Invest., 36, 1672, 1957. 

Bergstrom J, Burst P, Noree LO, Vinnars E. Intracellular free amino acid concentration in human muscle tissue. J. Appl. Physiol. 36 693-699, 1974. 

This compound cluster exhibits a two-ring, "open-chained, indolic chemical structure, and in contrast to other psychedelics it is all but inactive when taken orally unless accompanied by certain other compounds. Shortacting tryptamines are closely related to neurotransmitters (such as bufotenine), to MDA (a major botanical source of the snuffs belongs to the nutmeg family), to tryptophan (an essential amino acid produced in human digestion of proteins) and to psilocybin and psilocin (which are tryptamines of longer duration). DMT, the simplest member, occurs normally in the blood, brain and (in higher concentrations) in the cerebrospinal fluid. 

This metabolic activity is achieved by a turnover of amino acids and proteins that is as rapid as that of lipids and carbohydrates. In an adult human -400 g of body proteins is turned over each day. Of this -50 g replaces digestive enzymes and -15 g replaces hemoglobin. The amino acid concentration in plasma is small (total 3.2 mM, of which -25% is glutamine) but the turnover of -400 g day of protein is equal to the uptake and release back into the plasma of 4.6 mol of a-amino-iV, so that the average lifetime of an amino acid in the plasma is -5 min. Plasma amino acids are turned over with the same kind of rapidity as plasma glucose or free fatty acids. Like plasma glucose, the plasma amino acid concentration is remarkably constant, but it is not understood how this is regulated. 

Urea is a colorless, odorless crystalline substance discovered by Hilaire Marin Rouelle (1718—1779) in 1773, who obtained urea by boiling urine. Urea is an important biochemical compound and also has numerous industrial applications. It is the primary nitrogen product of protein (nitrogen) metabolism in humans and other mammals. The breakdown of amino acids results in ammonia, NH3, which is extremely toxic to mammals. To remove ammonia from the body, ammonia is converted to urea in the liver in a process called the urea cycle. The urea in the blood moves to the kidney where it is concentrated and excreted with urine. 

Iodine is concentrated in humans by the thyroid gland to form the iodo-amino acid thyroxine, which is essential to normal health and development. Iodine is a rather rare element (crustal abundance 0.00003 weight %, cf. Table 1.1), so the thyroid gland has become very efficient at scavenging iodide ion. As iodine is deficient in the diet in some locations, a small amount of iodide ion is routinely added to commercial table salt ( iodized salt ). 

Since animals tend to concentrate in their own proteins the sulfur amino acids contained in the plants diey eat, such animal products (meat. eggs, and cheese) are valuable sources of the essential sulfur amino acids in human diets. In regions where die diet is composed almost entirely of foods of plant origin, deficiencies of sulfur amino acids may be critical in human nutrition. Frequently, persons in such areas (also voluntary vegetarians) are also likely to suffer from a number of odier dietary insufficiencies unless supplemental sources are used. 

The —50 kDa band (48-53 kDa) is identified as dysbindin-1 A in our WESTERNS, because it runs close to the molecular mass of our histidine-tagged recombinant mouse dysbindin-1 A. Its identity is confirmed by the fact that it is recognized by antibodies we have recently generated to amino acid sequences in the CTR of human dysbindin-lA, but not found in dysbindin-lB, -2, or -3. The —50 kDa band is the most consistently observed dysbindin-1 band across tissues. We find it in all tissues examined to date the adrenal gland, heart, kidney, liver, lung, spleen, skeletal muscle, testes, spinal cord, cerebellum, striatum, hippocampus, and cerebral cortex (e.g., Figure 2.2-12a and c). In mouse and human synaptosomes, the —50 kDa isoform is heavily concentrated in the PSD fraction with a much lesser amount in the presynaptic membrane and no detectable amount in the synaptic vesicle fraction (Talbot et al., in preparation). 

One must conclude that hydrophobic interactions may stabilise the multilayer TRP-ARG sandwich of gpl30, in spite of the different character of these two amino acids, and in spite of the entropic penalty mentioned above. However the gpl30 crystals themselves came from a solution which contained glycerol molecules and sulfate ions, and both of these components were trapped in the crystals where they may have helped to stabilise the observed protein structure. It would not be altogether surprising if some alternative conformation or conformations of gpl30 may also occur in vivo, if those somewhat unphysiological substances are not present in the human body in sufficient concentrations to stabilise the structure as observed. 

Adibi. S- A., and Mercer, D- W. (1973). Protein digestion in human intestine as reflected in Luminal mucosal and plasma amino acid concentrations after meals. /, Cfin, biiesf, 52, 15B6-1594. 

Intestinal absorption of is low, ranging from 0.4% to 2.5%, so fecal output is mainly unabsorbed dietary chromium. Absorption is increased marginally by ascorbic acid, amino adds, oxalate, and other dietary factors. After absorption, chromium binds to plasma transferrin with an affinity similar to that of iron. It then concentrates in human liver, spleen, other soft tissue, and bone. Urine chromium output is around 0.2 to 0.3 U,g/day, the amount excreted being to some extent dependent upon intake. Paradoxically, urine output appears to be relatively increased at low dietary levels. Thus 2% is lost in urine at an intake of lOpg/day, but only 0.5% at an intake of 40pg/day. Both running and resistive exercise increases urine chromium excretion. 

In 1950, Schurr et al.1 determined the amino add concentrations in various tissues of the rat. When these data were used to calculate tissue/plasma ratios, it became apparent that the relative availability of plasma tryptophan to tissues was much less than that of the other amino acids. In 1957, McMe-nemy et al.2 described a unique property of tryptophan It was the only amino acid in human plasma that was largely bound to protein. This attribute, specifically the ratio of free to bound tryptophan in the blood, has much physiological significance. For example, only the small free fraction of plasma tryptophan has access to the brain. Factors that influence the equilibrium between free and bound tryptophan in the plasma have been considered to alter the availability of tryptophan to the brain, where it has special importance as a precursor of the neurotransmitter 5-hydroxy-tryptamine (serotonin).3 5 Tryptophan differs from other amino acids in that its concentration in plasma of rats increases (30 to 40%) after fasting, after insulin administration, or after consuming a carbohydrate meal.6... 

Wide daily fluctuations in the concentrations of plasma tryptophan, as well as of other amino acids, occur in healthy humans.7 Feigin et al.8 reported a diurnal rhythm for total whole-blood amino acid levels in healthy humans. Daily fluctuations have been observed for all of the nutritionally important amino acids.910 A number of investigators have studied factors that may influence diurnal fluctuations of plasma tryptophan in humans.1112 Many reports cite marked variations, usually decreased levels, of plasma tryptophan, under a variety of disease states. However, it is difficult to assess the importance of these observations. 

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