Leucine essentiality

Metabolic Functions. Zinc is essential for the function of many enzymes, either in the active site, ie, as a nondialyzable component, of numerous metahoenzymes or as a dialyzable activator in various other enzyme systems (91,92). WeU-characterized zinc metahoenzymes are the carboxypeptidases A and B, thermolysin, neutral protease, leucine amino peptidase, carbonic anhydrase, alkaline phosphatase, aldolase (yeast), alcohol... 

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. 

Alcohol dehydrogenase (5) and leucine a-ketoglutarate transaminase (33,34) contribute to the development of aroma during black tea manufacturing. Polyphenol oxidase and peroxidase are essential to the formation of polyphenols unique to fermented teas. 

Valine, Leucine, and Isoleucine. While leucine, valine, and isoleucine are all nutritionally essential... 

Not all proteins are nutritionally equivalent. Mote of some than of others is needed to maintain nittogen balance because different proteins contain different amounts of the various amino acids. The body s requirement is for specific amino acids in the correct proportions to replace the body proteins. The amino acids can be divided into two groups essential and nonessential. There are nine essential or indispensable amino acids, which cannot be synthesized in the body histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. If one of these is lacking or inadequate, then—regardless of the total intake of protein—it will not be possible to maintain nitrogen balance since there will not be enough of that amino acid for protein synthesis. 

The Rp toxins also have an additional residue at the N-terminus which extends the sheet one residue in that direction. This may be an indication that the structural difference arises from the substitution of F17 for L17 in RpII, because there is also leucine at position 17 in the A. xanthogrammica toxins. The structure of the core sheet is remarkably similar among the different toxins, considering that there is essentially no conservation of the residues involved in forming it, aside from the cystines. 

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. 

Ninhydrin assay. Ninhydrin reactivity was measured essentially as described previously (Moore and Stein, 1954 Moore, 1968) 100-pl aliquots were mixed with an equal volume of ninhydrin reagent in duplicate. After heating in a boiling water bath for 15 minutes and dilution with 0.80 ml ethanol/water (1 1 by vol.), the absorbance at 550 nm was measured with a Vitatron flow-through spectrophotometer. Standards comprised 0.0-0.5 mM leucine. 

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... 

Similarly, good results were obtained with poly-(i)-alanine, poly-(L)-leucine and poly-(i)-isoleucine, whereas with poly-(i)-vahne or random copolymers reduced chemical yields as weU as asymmetric induction were obtained. Chemical and optical yields are closely related in all cases. The enantiomeric excesses obtained increased as the average chain length of the catalyst increased varying from 10 to 30 amino acids (ee values between 50 to 99%). For high ee values it seems to be essential that the polymer chain is at least 10 units. The degree of asymmetric induction decreases as the temperature is raised. The amount of catalyst only influences the chemical yield, not the optical yield of... 

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. 

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