Threonine essential amino acid

See also - Table 5.1, Genetic Code, Glutathione, Metabolism of Serine, Glycine, and Threonine, Essential Amino Acids, Titration Curve of Glycine... 

See also Metabolism of Serine, Glycine, and Threonine, Essential Amino Acids... 

Because of the simplicity of swiae and poultry feeds, most feed manufacturers add vitamins (qv) and trace minerals to ensure an adequate supply of essential nutrients. Amino acids (qv) such as methionine [7005-18-7] lysiae [56-87-17, threonine [36676-50-3] and tryptophan [6912-86-3], produced by chemical synthesis or by fermentation (qv), are used to fortify swiae and poultry diets. The use of these supplements to provide the essential amino acids permits diets with lower total cmde proteia coateat. 

The nutritional value of a proteia can be improved by the addition of amino acids of low abundance ia that proteia. Thus the fortification of plant proteias such as wheat, com, and soybean with L-lysiae, DL-methionine, or other essential amino acids (L-tryptophan and L-threonine) is expected to alleviate some food problems (11). Such fortification has been widespread ia the feedstuff of domestic animals. 

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. 

Sundower Seed. Compared to the FAO/WHO/UNU recommendations for essential amino acids, sunflower proteins are low in lysine, leucine, and threonine for 2 to 5-year-olds but meet all the requirements for adults (see Table 3). There are no principal antinutritional factors known to exist in raw sunflower seed (35). However, moist heat treatment increases the growth rate of rats, thereby suggesting the presence of heat-sensitive material responsible for growth inhibitions in raw meal (72). Oxidation of chlorogenic acid may involve reaction with the S-amino group of lysine, thus further reducing the amount of available lysine. 

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. 

The complete identification of the amino acids which are essential in the diet is due to W.C. Rose (1938). His first attempts to replace casein with its constituents were unsuccessful because an essential amino acid component in the protein hydrolysate had been missed. After threonine had been isolated by him from casein and fibrin, and shown to be essential, Rose identified val, met, his, lys, phe, leu, ile, thr, and arg as... 

Because of their unique biological functions, a significant and growing part of new drug discovery and development is focused on this class of biomolecules. Their biological functions are determined by the exact arrangement, or sequence of different amino acids in their makeup. There are 20 naturally occurring amino acids, 8 of which are essential amino acids, namely, l-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-valine, l-threonine, and L-tryptophan. 

Kirchgessner and Steinhart (52) studied the in vitro digestion of soy protein isolate with pepsin. They showed that a relatively higher percentage of the essential amino acids threonine, valine, isoleucine, leucine and phenylalanine were found in the undigested residue and therefore would be present in lower proportions in the hydrolysate. Myers et al. ( ) hydrolyzed a soy protein isolate with a fungal acid protease. They also found that the essential amino acid content of the hydrolyzate was lower than the isolate, but, as prepared by their continuous process, the hydrolyzate PER was not significantly reduced as compared to the isolate PER. 

Methionine, threonine, lysine, isoleucine, valine, and leucine are essential amino acids. Their biosynthetic pathways are complex and interconnected (Fig. 22-15). 

FIGURE 22-15 Biosynthesis of six essential amino acids from oxalo-acetate and pyruvate in bacteria methionine, threonine, lysine, isoleucine, valine, and leucine. Here, and in other multistep pathways, the enzymes are listed in the key. Note that L,L-a,e-diaminopimelate, the product of step (HI), is symmetric. The carbons derived from pyruvate (and the amino group derived from glutamate) are not traced beyond this point, because subsequent reactions may place them at either end of the lysine molecule. 

A distribution of amino acids in dietary proteins can be obtained accordingly by taking both animal and plant proteins at a ratio of 1 3-4. Although plant proteins are lower cost, they are markedly deficient in some essential amino acids. Their protein efficiency is low without addition of deficient ammo acids. Enrichment of human and animal diets with free amino acids, such as lysine, methionine, threonine, and tryptophan, as a substitute for animal proteins, has proved successful. 

Lysine, threonine Corynebacterium glutamicum, Brevibacterium flavum, Escherichia coli Essential amino-acids, added to supplement low grade protein... 

The description of ci-amino acids as D or L is a holdover from an older nomenclature system. In this system (5)-alanine is called L-alanine. The enantiomer would be D- or ( )-serine. The l (laevo, turned to the left D = dextro, turned to the right) designation refers to the ct-carbon in the essential amino acids. In alanine, there is a single a-carbon that is asymmetric. When two asymmetric centers are present as in L-threonine, the stereochemistry of both carbons must be considered. The common form of L-threonine is the 25,3R stereoisomer. 

Human beings are able to synthesize 10 of the amino acids, termed nonessentiul amino acids, from other compounds in the diet. However, the other 10 amino acids, termed essential amino acids, cannot be synthesized by humans (or are synthesized only in small amounts) and must be obtained from protein sources in the diet. The essential amino acids are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. 

Proteins that are severely deficient in one or more of the essential amino acids are called incomplete proteins. If the protein in a person s diet comes mostly from one incomplete source, the amount of human protein that can be synthesized is limited by the amounts of the deficient amino acids. Plant proteins are generally incomplete. Rice, com, and wheat are all deficient in lysine. Rice also lacks threonine, and corn also lacks tryptophan. Beans, peas, and other legumes have the most complete proteins among the common plants, but they are deficient in methionine. 

Although all of the amino acids listed in Table SO-1 are present in the proteins of the human body, not all of them need to be in the food. Experiments have been carried out which show that nine of the amino acids are essential to man. 1 hese nine essential amino acids are histidine, lysine, tryptophan, phenylalanine, leucine, isoleucine, threonine, methionine, and valine. The human body seems to be able to manufacture the others, which are called the non-essential amino acids. Some organisms that we usually consider to be simpler than man have greater powers than the human organism, in that they are able to manufacture all of the amino acids from inorganic constituents. The red bread mold, Neurospora, has this power. 

Most of the prokaryotic and many eukaryotic organisms (plants) are capable of synthesizing all the amino acids present in the protein. But higher animals including man possess this ability only for certain amino acids. The other amino acids, which are needed for normal functioning of the body but cannot be synthesized from metabolic intermediates, are called essential amino acids. These must be obtained from the diet and a deficiency in any one of the amino acids prevents growth and may even cause death. Methionine, Threonine, Tryptophan, Valine, Isoleucine, Leucine, Phenylalanine and Lysine are the essential amino acids, however, Histidine and Arginine are considered semi essential amino acids as it can be partly synthesized by the body. 

Nine amino acids cannot be synthesized in the body and, therefore, must be present in the diet in order for protein synthesis to occur. The essential amino acids are lysine, isoleucine, leucine, threonine, valine, tryptophan, phenylalanine, methionine, and histidine. 

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