Essential amino acids levels

Tamarind seeds contain 13% crade protein, which is comparable to a previous report (Balogun and Fetuga, 1986, cited in 4)). According to Ishola and collaborators (9), tamarind seeds are a good sonrce of protein (269.3 g/kg). Amino acid profdes of tamarind reveal that the proteins contain fairly balanced essential amino acid levels (Table VII). All essential amino acid levels, except threonine, valine and tiytophan, are higher than the FAO/WHO reference pattern (Table VIII). Tamarind seeds conld, therefore, be used as a less expensive source of protein to help alleviate protein malnutrition found so widespread in many developing countries ((4) cited in (5)). 

Lofberg E, et al. Correction of acidosis in dialysis patients increases branched-chain and total essential amino acid levels in muscle. Clin Nephrol 1997 48 230-237. 

Fig. 8. Summary diagram representing possible changes in circulating hormones, essential amino acid levels and liver protein synthesis with feeding, fasting and refeeding in trout. (McMillan and Houlihan 1990a)...

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

AA biosynthesis. At an ever deeper level it is possible that high concentrations of the product AA can inhibit expression of the gene for formation of the RNA needed for enzyme synthesis. This form of suppression of gene action over many generations could lead to loss of the gene, causing the AA to become an essential amino acid. 

There are a few substances that can reduce serotonin, norepinephrine and/or dopamine rapidly and substantially, reducing them to levels thought to be lower than those of depressed patients.23 That is what reserpine was supposed to do and, as we have seen, it did not cause depression - despite the early clinical impression that it did. Other substances have been used in later studies, the most common of which are amino-acid mixtures that lack the essential amino acids needed by the body to produce these neurotransmitters. For example, having people drink a beverage that is rich in amino acids, but does not contain tryptophan (the amino acid needed to produce serotonin), lowers their serotonin levels within a couple of hours. 

The bulk hydrogen isotopic composition of amino acids has been shown to depend on animal trophic level (Birchall et al. 2005). Furthermore, compound-specific hydrogen isotopic analyses of amino acids may help elucidate the mechanism behind this enrichment, by determining the differences in 8D value between essential and non-essential amino acids, and may also provide a further palaeodietary indicator (e.g. Corr et al. 2005). However, amino acids are highly functional, with both amino and carboxyl extremely... 

A specific example of the law of the minimum on a molecular level is the essential amino acids. The need for essential amino acids in human nutrition shows that one amino acid cannot substitute for another. Substitution of one amino acid for another can lead to disease. This is shown, for example, in sickle... 

The presence of residual unbound transition-metal ions on a dyed substrate is a potential health hazard. Various eco standards quote maximum permissible residual metal levels. These values are a measure of the amount of free metal ions extracted by a perspiration solution [53]. Histidine (5.67) is an essential amino acid that is naturally present as a component of perspiration. It is recognised to play a part in the desorption of metal-complex dyes in perspiration fastness problems and in the fading of such chromogens by the combined effects of perspiration and sunlight. The absorption of histidine by cellophane film from aqueous solution was measured as a function of time of immersion at various pH values. On addition of histidine to an aqueous solution of a copper-complex azo reactive dye, copper-histidine coordination bonds were formed and the stability constants of the species present were determined [54]. Variations of absorption spectra with pH that accompanied coordination of histidine with copper-complex azo dyes in solution were attributable to replacement of the dihydroxyazo dye molecule by the histidine ligand [55]. 

Characteristically, legume seeds are rich in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal diets. Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water solubility, water and fat binding and emulsification. Thus soybean flours, protein concentrates and isolates have been used widely as nutritional supplements and functional ingredients in foods. 

From amino acid compositions, evaluations o7" the nutritional potentials of cucurbit meals and globulins can be calculated according to FA0/WH0 (54). The A E ratios, which are the amounts of each essential amino acid relative to the total amount of essential amino acids, are shown in Table II. These data indicate that, like most other oilseeds, cucurbit seeds are deficient in lysine and sulfur-containing amino acids. However, sulfur-containing amino acids are considerably high in CitrullI us colocynthis (egusi, ancestral watermelon) seed protein and exceed the suggested level in FA0/WH0 reference protein (55). 

Infants with classic phenylketonuria (PKU) are normal at birth but if untreated show slow development, severe mental retardation, autistic symptoms, and loss of motor control. Children may have pale skin and white-blonde hair. The neurotoxic effects relate to high levels of phenylalanine and not to the phenylketones from which the name of the disease derives. Infants are routinely screened a few days after birth for blood phenylalanine level. Treatment consists of a life-long semisynthetic diet restricted in phenylalanine (smalt quantities are necessary because it is an essential amino acid). Aspartame (N-aspartyl-phenylalanine methyl ester), which is widely used as an artificial sweetener, must be strictly avoided by phenyiketonurics. 

One trick is the administration of benzoate or phenylac-etate. These acids react with glycine or glutamine, respectively, to produce complexes (conjugates) which are excreted in the urine (Figure 10.10). This decreases the plasma level of either of these non-essential amino acids... 

Today aspartame is used in more than 6,000 food products. Aspartame is 160 times as sweet as sucrose based on mass equivalents. Approximately 16,000 tons are consumed annually on a global basis, with approximately 8,000 tons used in the United States and 2,500 tons in Europe. In the body aspartame is metabolized into its three components aspartic acid, phenylalanine, and methanol (Figure 11.1). Aspartic acid is a nonessential amino acid and phenylalanine is an essential amino acid. The condition called phenylketonuria (PKU) is a genetic disorder that occurs when a person lacks the enzyme phenylalanine hydroxylase and cannot process phenylalanine. This results in high phenylalanine blood levels that are metabolized into products one of these is phenylpyruvate, which contains a ketone group and... 

In addition to carbohydrates, extrafloral nectar may contain variable amounts of proteins, amino acids, and lipids (Baker et al., 1978 Smith et al., 1990). The particular amino acid composition can increase the attractiveness of extrafloral nectar as a food source (Lanza, 1988). Nevertheless, extrafloral nectar by itself falls short from providing a well-balanced diet. Low amino acid levels or the absence of certain essential amino acids forces nectar consumers to seek out supplementary protein sources, thereby stimulating predation. 

Homocysteine (Hey) metabolism is closely linked to that of the essential amino acid methionine and thus plays a central role in several vital biological processes. Methionine itself is needed for protein synthesis and donates methyl groups for the synthesis of a broad range of vital methylated compounds. It is also a main source of sulphur and acts as the precursor for several other sulphur-containing amino acids such as cystathionine, cysteine and taurine. In addition, it donates the carbon skeleton for polyamine synthesis [1,2]. Hey is also important in the metabolism of folate and in the breakdown of choline. Hey levels are determined by its synthesis from methionine, which involves several enzymes, its remethylation to methionine and its breakdown by trans-sulphuration. 

The essential amino acid lysine (2,5-diaminohexanoic acid) can be degraded via two pathways, viz. the so-called saccharopine pathway and the pipecolic acid (PA) pathway. Both pathways merge at the level of a-aminoadipic acid semialdehyde (AASA). It is generally accepted that the saccharopine pathway constitutes the major breakdown pathway. However, the PA pathway has attracted much attention since the discovery of the association between the presence of elevated PA levels and Zellweger syndrome almost 40 years ago. Mainly because the analysis of amino acids was the primary biochemical approach for studying presumed inborn errors of metabolism, PA in Zellweger syndrome was discovered even before it was realized that this disorder was based on a defect of peroxisomal functions. 

Depletion of ATP is caused by many toxic compounds, and this will result in a variety of biochemical changes. Although there are many ways for toxic compounds to cause a depletion of ATP in the cell, interference with mitochondrial oxidative phosphorylation is perhaps the most common. Thus, compounds, such as 2,4-dinitrophenol, which uncouple the production of ATP from the electron transport chain, will cause such an effect, but will also cause inhibition of electron transport or depletion of NADH. Excessive use of ATP or sequestration are other mechanisms, the latter being more fully described in relation to ethionine toxicity in chapter 7. Also, DNA damage, which causes the activation of poly(ADP-ribose) polymerase (PARP), may lead to ATP depletion (see below). A lack of ATP in the cell means that active transport into, out of, and within the cell is compromised or halted, with the result that the concentration of ions such as Na+, K+, and Ca2+ in particular compartments will change. Also, various synthetic biochemical processes such as protein synthesis, gluconeogenesis, and lipid synthesis will tend to be decreased. At the tissue level, this may mean that hepatocytes do not produce bile efficiently and proximal tubules do not actively reabsorb essential amino acids and glucose. 

Nutritive value of foods and feedstuffs depends to a large degree on protein level and quality, i.e., the relative amounts of the component amino acids compared to the requirements of the animal for various metabolic functions. The cereal grains are notoriously low in certain essential amino acids. Usually lysine is the first or second limiting amino acid. The grain of rye (Secale cereale L.) exhibits an amino acid profile superior to that of other cereal grains, especially wheat (1,2,3,4,5). Despite this fact, lysine is still the first limiting amino acid in rye in most instances (6,7). 

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