Amino acid requirements

Proteins. Proteins (qv) supply amino acids (qv), palatabiHty enhancement, and, when present in more than requited amounts, energy as the proteins are degraded and nitrogen compounds excreted. Dogs and cats can consume and meet amino acid requirements in the form of pure amino acids with complete success. However, animal tissue cannot differentiate between pure, plant, or animal sources of those amino acids, and those amino acids can be obtained much more economically from either plant or animal proteins. 

Amino acid compositions of the four oilseeds are given in Table 3 along with the amino acid (see Amino ACIDS) requirements for humans suggested by a Joint FAO/WHO/UNU Expert consultation. 

Table 3. Amino Acid Composition of Defatted Oilseed Meals and Amino Acid Requirements, mg/g Crude Protein...

Essential amino acid requirements for humans recommended by FAO/WHO/UNU (21). An essential amino acid is one that caimot be synthesized by... 

Cottonseed. When compared with FAO/WHO/UNU essential amino acid requirements (see Table 3), cottonseed proteins are low in lysine, threonine, and leucine for 2 to 5-year-old children, yet meet all requirements for adults. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Specific methods to separate tire amino acid required from its contaminant products, such as medium components and other amino adds, are proceeded by removal of the cells and proteineous material from the culture broth. 

Eagle, H. (1955). The specific amino acid requirements of a mammalian cell (strain L) in tissue culture. J. Bio. Chem. 214, 83 85. 

Fuller MF, Garlick PJ Human amino acid requirements. Annu RevNutr 1994 14 217. 

Early rhizosphere establishment is demonstrated in 2-3 day-old wheat plants when there is a shift towards a population of amino acid requiring bacteria (19). Maximum activity and numbers of rhizosphere microorganisms correlated with maximum vegetative plant development (20-22). Once established, the rhizosphere remains qualitatively similar, but quantitatively increases from seedling stage to maturity (23). After maturity the bacterial population reverts to a population similar to that in non-rhizospheric soils. 

Plants synthesize all the amino acids they require. They do so using as raw material carbohydrates, which they make during photosynthesis, and nitrogen, derived from nitrate ions absorbed from the soil. Animals cannot synthesize all the amino acids required for their regular living, health, and growth. Those they cannot synthesize, known as the essential amino acids, are acquired from plants and/or animals they consume as food. Human beings, for example, acquire nine essential amino acids from their diet. 

A GC analysis of amino acids requires a derivatisation step to increase the volatility of the amino acids. Generally, norleucine and/or norvaline are the internal standards added to the hydrolysate to check the derivatisation yield. According to the experimental method applied, the limits of detection (LOD) vary in the range 10 100 pg for each amino acid. Regarding the chromatographic columns, as most of the derivatives are esters barely polar compounds the most commonly used are fused-silica capillary columns with a low... 

The other nine amino acids are essential and must be taken from the diet. Notice that some of the amino acids require other amino acids for their synthesis. Exam questions usually center on whether or not an amino acid is essential and the metabolites that serve as precursors for specific amino acids. 

It is noteworthy that there is another limiting factor in the choice of amino acid types at the junction sites which affect the enzymatic process of the intein. For example, in the case of SceVMA (also called PI-Seel) from the IMPACT system, proline, cysteine, asparagine, aspartic acid, and arginine cannot be at the C-terminus of the N-terminal target protein just before the intein sequence. The presence of these residues at this position would either slow down the N-S acyl shift dramatically or lead to immediate hydrolysis of the product from the N-S acyl shift [66]. The compatibility of amino acid types at the proximal sites depends on the specific inteins and needs to be carefully considered during the design of the required expression vectors. The specific amino acid requirements at a particular splicing site depends on the specific intein used and is thus a crucial point in this approach. 

There are several reasons for anticipating that the quantities of the various amino acids required will be found to be distinctive for each individual. Many of the enzymes involved in the metabolism and inter-conversions of amino acids are known, and the differing efficiencies of these enzymes and those involved in protein synthesis in different individuals should be the basis for needs which are quantitatively distinctive for each individual. 

Little attention has been paid to the question of inter-individual differences in amino acid requirements. In the attempts to determine what the human adult requirements for individual essential amino acids are (for maintaining nitrogen equilibrium), studies have been made on individual young men. The following inter-individual ranges... 

Anthony A. Albanese, Protein and Amino Acid Requirements of Mammals, Academic Press, New York, N.Y., 1950. 

Onoue, Y. and Mori, M., Amino acid requirements for the growth and enterotoxin production by Staphylococcus aureus in chemically defined media, Int. J. Food Microbiol., 36, 77-82, 1997. 

The test is commonly employed as an initial screen for genotoxic activity and, in particular, for point mutation-inducing activity. It detects point mutations, which involve substimtion, addition or deletion of one or a few DNA base pairs. The reverse mutation test in either Salmonella typhimurium or Escherichia coli detects mutation in an amino acid requiring strain (histidine or tryptophan, respectively) to produce a strain independent of an outside supply of amino acid. The principle of the test is that it detects mutations, which revert mutations present in the test strains and restore the functional capability of the bacteria to synthesize an essential amino acid. The revertant bacteria are detected by their ability to grow in the absence of the amino acid required by the parent test strain. 

The active form of vitamin Be, pyridoxai phosphate, is the most important coenzyme in the amino acid metabolism (see p. 106). Almost all conversion reactions involving amino acids require pyridoxal phosphate, including transaminations, decarboxylations, dehydrogenations, etc. Glycogen phosphory-lase, the enzyme for glycogen degradation, also contains pyridoxal phosphate as a cofactor. Vitamin Be deficiency is rare. 

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