Amino acid essential

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. 

---

As constituents of proteins the amino-acids are important constituents of the food of animals. Certain amino-acids can be made in the body from ammonia and non-nitrogenous sources others can be made from other amino-acids, e.g. tyrosine from phenylalanine and cystine from methionine, but many are essential ingredients of the diet. The list of essential amino-acids depends partly on the species. See also peptides and proteins. 

M.p. 207°C. The naturally occurring substance is dextrorotatory. Arginine is one of the essential amino-acids and one of the most widely distributed products of protein hydrolysis. It is obtained in particularly high concentration from proteins belonging to the prolamine and histone classes. It plays an important role in the production of urea as an excretory product. 

H2N-CH2 [CH2j3.CH(NH2) COOH. Colourless needles, m.p. 224 C (decomp.), very soluble in water, insoluble in alcohol. L-(-H)-Lysine is one of the basic amino-acids occurring in particularly large quantities in the protamine and histone classes of proteins. It is an essential amino-acid, which cannot be synthesized by the body and must be present in the food for proper growth. It can be manufactured by various fermentation processes or by synthesis. 

C11H12N2O2. M.p. 289°C. L-Tryptophan is an essential amino-acid, its presence in the food of animals is necessary for proper growth. It is present in small quantities in the hydrolysis products of most proteins, although absent in certain vegetable proteins. 

Our bodies can make some of Ihe ammo acids shown m Ihe fable The olhers which are called essential amino acids, we have to gel from whal we eal... 

An essential amino acid which must be present in the diet of animals to ensure normal growth... 

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. 

Gelatin can be a source of essential amino acids when used as a diet supplement and therapeutic agent. As such, it has been widely used in muscular disorders, peptic ulcers, and infant feeding, and to spur nail growth. Gelatin is not a complete protein for mammalian nutrition, however, since it is lacking in the essential amino acid tryptophan [73-22-3] and is deficient in sulfur-containing amino acids. 

Casein. Milk contains proteins and essential amino acids lacking in many other foods. Casein is the principal protein in the skimmed milk (nonfat) portion of milk (3—4% of the weight). After it is removed from the Hquid portion of milk, whey remains. Whey can be denatured by heat treatment of 85°C for 15 minutes. Various protein fractions are identified as a-, P-, and y-casein, and 5-lactoglobulin and blood—semm albumin, each having specific characteristics for various uses. Table 21 gives the concentration and composition of milk proteins. 

Table 4. Essential Amino Acid Content of Nuts ...

Amino acids are important components of the elementary nutrients of living organisms. For humans, ten amino acids are essential for existence and must be iagested ia food. The nutritional value of proteias is governed by the quantitative and qualitative balance of iadividual essential amino acids. ... 

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. 

Feeding standards, which have been instituted nationally, indicate the amount of the essential amino acids (together with other nutrients) for the rational breeding of domestic animals. The feeding standards of the National Research Council (NRC) of the United States and Agricultural Research Council (ARC) of the United Kingdom are well known (the former indicates the minimal amount and the latter shows the recommended amount). 

Amino acids essential for young rats (98) and fishes (99) have been reviewed. Rats preferably eat a diet with sufficient amounts of essential amino acids rather than one that is deficient (100). Each essential amino acid, consumed in self-selection, has been reviewed (101). A protein diet with an excess of essential amino acids has been described as a poor protein diet from investigations that showed remarkable growth inhibition and occurrence of fatty fiver disease in rats (102). This is called amino acid imbalance (103). 

Currently available proteins are all deficient to greater or lesser extent in one or more of the essential amino acids. The recently advanced plastein reaction (229) has made it possible to use protein itself as substrate and to attach amino acid esters to the protein with high efficiency. By this method, soy bean protein (which is deficient in methionine) has been improved to the extent of having covalently attached L-methionine at 11%. 

Data Sheets ofMmino Mcids, Part 1 (1985), The Japan Essential Amino Acids Association, Tokyo, Japan, 1985 R. C. Weast, ed. Handbook of Chemistry and Physics, 67th edition, CRC Press, Inc., Boca Raton, Fla., 1986, p. C-702. 

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

Free substitution of protein meals ia feeds is much more restricted than interchange of oils ia foods. Because of a good balance of essential amino acids, soybean meal is an indispensable ingredient for efficient feeding of nonmminants, eg, poultry and swine. Soybeans provide ca 60% of the world s protein meals, including fish meal (Table 14). Of the 30.0 x 10 t of soybean meal produced in the United States in 1994—1995, 24.2 x 10 t was used domestically, primarily in feeds, and 5.7 x 10 t was exported (50). In the United States, poultry consume the largest share of soybean meal, followed by swine. Lesser amounts are fed to beef and dairy catde. Soybean meal is a principal ingredient in many pet foods (see Feeds and feed additives). 

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. 

Taufine [107-35-7] (2-aminoethanesulfonic acid), is the only known naturally occurring sulfonic acid. The material is an essential amino acid for cats and is used extensively by Ralston Putina Company as a food supplement ia cat food manufacture. Approximately 5,000—6,000 t of tautine (synthetic and natural) were produced ia 1993 50% for pet food manufacture, 50% ia pharmaceutical appHcations (114). 

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

Purification. The objective of crystallization also can be purification of a chemical species. For example, L-isoleucine (an essential amino acid) is separated by crystallization from a fermentation broth that has been filtered and subjected to ion exchange. The recovered crystals contain impurities deleterious to use of the product, and these crystals are, therefore, redissolved and recrystalHzed to enhance purity. 

Although essential amino acids are requited by both host and tumor, deprivation of select essential amino acids for 2—3 weeks is tolerated by the host yet exerts a pronounced antiproliferative effect on the tumor. Thus, treatment of mice with indole-3-alkane-a-hydroxylase [63363-76-8] from Pseudomonas, which transforms L-tryptophan [73-22-3] to 3-indolylglycaldehyde, lowers the concentration of L-tryptophan in plasma, brain, and lungs, and inhibits the growth of a variety of tumors (32—34). 

One fflnino acid often serves as the biological precursor to another. L-Phenylala-nine is classified as an essential amino acid, whereas its p-hydroxy derivative, L-tyro-sine, is not. This is because animals can convert L-phenylalanine to L-tyrosine by hydrox-ylation of the aromatic ring. An arene oxide (Section 24.7) is an intennediate. 

Essential amino acids (Section 27.1) Amino acids that must be present in the diet for normal growth and good health. 

Humans are able to synthesize only 11 of the 20 amino acids in proteins, called nonessential amino acids. The other 9, called essential amino acids, are biosynthesized only in plants and microorganisms and must be obtained in our diet. The division between essential and nonessential amino acids is not clearcut, however tyrosine, for instance, is sometimes considered nonessential because humans can produce it from phenylalanine, but phenylalanine itself is essential and must be obtained in the diet. Arginine can be synthesized by humans, but much of the arginine we need also comes from our diet. 

Biological examples of pericyclic reactions are relatively rare, although one much-studied example occurs during biosynthesis in bacteria of the essential amino acid phenylalanine. Phenylalanine arises from the precursor chorismate,... 

WEB Glycine, an essential amino acid, has the formula NH2CH2COOH. Its skeleton structure has C—C and C—N bonds but no N—O bonds. Write its Lewis structure. 

These are essential amino acids that cannot be synthesized by the body and therefore must be obtained from the diet... 

---