Proteins amino acid requirements

Determination of the Daily Requirement and Recommended Daily Allowance for Protein Amino Acid Requirements Protein Quality... 

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. 

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

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. 

Most HPLC instruments monitor sample elution via ultraviolet (UV) light absorption, so the technique is most useful for molecules that absorb UV. Pure amino acids generally do not absorb UV therefore, they normally must be chemically derivatized (structurally altered) before HPLC analysis is possible. The need to derivatize increases the complexity of the methods. Examples of derivatizing agents include o-phthaldehyde, dansyl chloride, and phenylisothiocyanate. Peptides, proteins, amino acids cleaved from polypeptide chains, nucleotides, and nucleic acid fragments all absorb UV, so derivatization is not required for these molecules. 

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. 

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

Iodine is required for the formation of amino acids that act as thyroid hormones. The amino acids thyroxine and triiodothyronine, both derived from tyrosine, a protein amino acid, provide examples. 

Alanine and Glutamine in the Blood Normal human blood plasma contains all the amino acids required for the synthesis of body proteins, but not in equal concentrations. Alanine and glutamine are present in much higher concentrations than any other amino acids. Suggest why. 

The precise manner in which proteins with zinc fingers bind to DNA differs from one protein to the next. Some zinc fingers contain the amino acid residues that are important in sequence discrimination, whereas others appear to bind DNA nonspecifically (the amino acids required for specificity are located elsewhere in the protein). Zinc fingers can also function as RNA-binding motifs—for example, in certain proteins that bind eukaryotic mRNAs and act as translational repressors. We discuss this role later (Section 28.3). 

Dietary protein provides essential amino acids. The quality of a protein is a measure of its ability to provide the essential amino acids required for tissue maintenance. Proteins from animal sources, in general, have a higher quality protein than that derived from plants. However, proteins from different plant sources may be combined in such a way that the result is equivalent in nutritional value to animal protein. 

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