Leucine essential amino acid

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. 

Humans have a limited capacity to synthesize amino acids de novo, but extensive interconversions can occur. Those amino acids which cannot be formed within the body and must be supplied by the diet are called essential . Members of this group, which includes the branched chain amino acids leucine and valine, and also methionine and phenylalanine, are all dietary requirements. Such essential amino acids may be chemically converted, mainly in the liver, into the non-essential amino acids. The term non-essential does not equate with not biochemically important but simply means they are not strict dietary components. 

Second, the essential amino acids leucine, isoleucine, and phenylalanine are precursors for several additional tomato flavor elements. Here, too, these flavor elements are important flavor constituents in other fruits, including strawberries and apples. They are also found in breads, cheeses, wine, and beer. 

The female-produced sex pheromone of the scarab beetle, Phyllophaga lanceolata was identified as the methyl ester of an essential amino acid, L-leucine. Three amino acid derivatives were identified in the extracts of pheromone glands of the scarab beetle, Phyllophaga elenans. These were... 

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. 

The branched-chain amino acids, isoleucine, leucine, and valine, are essential amino acids. In contrast to other amino acids, they are metabolized primarily by the peripheral tissues (particularly muscle), rather than by the liver. Because these three amino acids have a similar route of catabolism, it is convenient to describe them as a group (see Figure 20.10). 

Correct answer = D. Methionine is the precursor of cysteine. An increase in gluconeogenesis releases increased ammonia and results in increased urea production. The essential amino acids leucine and lysine are ketogenic. Ornithine and citrulline are amino acids that are intermediates in the urea cycle, but are not found in tissue proteins. 

In a rare autosomal recessive condition (discovered in 1954) the urine and perspiration has a maple syrup odor/ High concentrations of the branched-chain 2-oxoacids formed by transamination of valine, leucine, and isoleucine are present, and the odor arises from decomposition products of these acids. The branched-chain amino acids as well as the related alcohols also accumulate in the blood and are found in the urine. The biochemical defect lies in the enzyme catalyzing oxidative decarboxylation of the oxoacids, as is indicated in Fig. 24-18. Insertions, deletions, and substitutions may be present in any of the subunits (Figs. 15-14,15-15). The disease which may affect one person in 200,000, is usually fatal in early childhood if untreated. Children suffer seizures, mental retardation, and coma. They may survive on a low-protein (gelatin) diet supplemented with essential amino acids, but treatment is difficult and a sudden relapse is apt to prove fatal. Some patients respond to administration of thiamin at 20 times the normal daily requirement. The branched-chain oxoacid dehydrogenase from some of these children shows a reduced affinity for the essential coenzyme thiamin diphosphate.d... 

Proteins are either complete or incomplete. Complete protein simply means that it contains at least the minimal amounts of amino acids to sustain life. Which of course under lines the fact that a high protein "content" does not necessarily mean a high quality protein. It is the essential amino acid pattern and ratio that counts most. The essential amino acids are L-Leucine, L-Isoleucine, L-Valine, (These three are branch chain amino... 

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. 

A minor pathway of valine catabolism is concerned with its conversion to leucine. Because leucine is an essential amino acid, its synthesis from valine is clearly not sufficiently significant to meet the organism s daily demand for leucine. In this reaction, isobutyryl-CoA (see Figure 20.20) is condensed with a molecule of acetyl-CoA to give /3-ketoisocaproate, which is then transaminated to give (3-leucine. A mutase is then used to convert /3-leucine to leucine. This mutase... 

The liver plays a central role in the synthesis of nearly all circulating proteins. Plasma contains 60-80 g/L of protein and this is turned over at a rate of approximately 250 g/day. A variety of proteins are constructed in the liver using amino acids (Aa) as their basic building blocks. Amino acids are categorised as essential and non-essential , the former being a requirement of dietary intake as they cannot be constructed in vivo, whereas the latter can be synthesised hepatically. The essential amino acids are further categorised as branched-chain amino acids (BCAA leucine, valine, isoleucine) or aromatic amino acids (AAA phenylalanine, tyrosine, methionine) according to their structure. Table... 

Oxo-isovalerate may be formed by the transamination of valine it is also the immediate precursor of valine biosynthesis and an intermediate in the synthesis of leucine (both are essential amino acids in mammals). Oxo-lso-valerate undergoes a hydroxymethyl transfer reaction, in which the donor is... 

On the other hand, other studies focused on O. oeni amino acid requirements for growth and malolactic fermentation in several growth media (Tracey and Britz 1989). Remize et al. (2006) determined the essential amino acids for the growth of five different strains of Oenococcus oeni. These amino acids corresponded to glutamic acid, methionine, phenylalanine, serine and tyrosine for all the strains studied. They also found that the amino acids valine, leucine, tryptophan, isoleucine, histidine and arginine were essential or necessary for the strains studied, but that the amino acids alanine, glycine and proline were not essential. 

This discussion of the metalloexopeptidases has focused on the general role of these enzymes in the conversion of dietary proteins into amino acids. In particular, the apparent synergistic relationship which the pancreatic carboxypeptidases have with the major endopeptidases, trypsin, chymotrypsin, and pepsin, in order to facilitate formation of essential amino acids has been stressed. The chemical characteristics, metalloenzyme nature, and mechanistic details of a representative of each class of exopeptidase have been presented. Leucine aminopeptidase from bovine lens was shown to be subject to an unusual type of metal ion activation which may be representative of a more general situation. Carboxypeptidase A of bovine pancreas was discussed in terms of its three-dimensional structure, the implications of x-ray crystallography to mecha ... 

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. 

Leucine is an essential amino acid and is consumed as part of a normal diet. It is generally regarded as a nontoxic and nonirritant material. It is moderately toxic by the subcutaneous route. 

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