Isoleucine, phenylalanine, methionine

Table 5.2 lists the amino acid molar ratios determined for LHCP from several plant sources, and compares these results with the mean values obtained for the main glycopeptide subfraction (peak I in Table 5.1) from microbubble surfactant. It can be seen from Table 5.2 that the amino acid composition of LHCP clearly resembles that of the main glycopeptide subfraction. Specifically, in both cases nonpolar residues represent a majority and near constant fraction (i.e., 59-62%) of the amino acid composition, with the relative amounts of such residues in practically all individual cases listed following the pattern glycine > leucine, alanine, valine, proline > isoleucine, phenylalanine > methionine, tryptophan (Table 5.2). Accordingly, the glycopeptide fraction of microbubble surfactant may represent a degradation product of the light-harvesting chlorophyll a/b-protein, which is well known (ref. 373-375) to be extremely widely distributed in terrestrial, freshwater, and salt-water environments (cf. ref. 379).

A series of various enantiomerically pure amino acid ester isocyanates (for example 452) has been synthesized in yields of 72-95% by carbonylation of the appropriate amino acid ester hydrochlorides (for example 451) with phosgene [311]. The products are based on the amino acids alanine, valine, leucine, isoleucine, phenylalanine, methionine, serine, and glutamic acid. 

Glucosinolates are derived from amino acids. The precursor amino acids comprise seven protein amino acids (alanine, valine, leucine, isoleucine, phenylalanine, tyrosine, and tryptophan), a number of chain-elongated methionines (CH3-S-(CH2)2-(CH2)n-CH(NH2)-COOH, n = 1-9), and chain-elongated... 

L Isoleucine, leucine, methionine, phenylalanine, tryptophan, tyrosine, valine X... 

The properties of polypeptides and proteins are determined to a large extent by the chemistry of the side chain groups, which may be summarized briefly as follows. Glycine in a peptide permits a maximum of conformational mobility. The nine relatively nonpolar amino acids-alanine, valine, leucine, isoleucine, proline, methionine, phenylalanine, tyrosine, and tryptophan-serve as building blocks of characteristic shape. Tyrosine and tryptophan also participate in hydrogen bonding and in aromatic aromatic interactions within proteins. 

Luminal Abluminal Blood to brain isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, tyrosine, valine (facilitative, bidirectional) Arginine, lysine, ornithine... 

Cheese Ripening. Rennet plays a major role in the texture and flavor development of cheese during the ripening process. Besides the rapid cleavage of the key phenylalanine-methionine bond to coagulate milk, chymosin has been shown to hydrolyze at least 22 other bonds in the casein molecules. The favored amino acids at the point of cleavage are leucine, isoleucine and phenylalanine. 

Figure 2 Hinged-lid model of fast inactivation of Na+ channels. Bird s eye view of the channel that consists of four similar repeats (l-IV). The channel is shown cut and spread open between repeats I and IV to allow a view of the intracellular loop between repeats III and IV. The loop acts as the inactivation gate whose hinge GG (a pair of glycines) allows it to swing between two positions the open channel state and the inactivated closed state where the inactivation particle IFM (the amino acids isoleucine, phenylalanine, and methionine) binds to its acceptor.

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. 

The process of amino acid accumulation is catalyzed by at least five different Na, amino acid-symporters transporting (i) asparagine and glutamine, (ii) arginine, lysine and histidine, (iii) alanine, glycine, serine and threonine, (iv) valine, leucine, isoleucine and methionine and (v) phenylalanine, tyrosine and tryptophane. One more symporter seems to be involved in the uptake of glutamate and aspartate. Cysteine is not transported and inhibits the transport of other amino acids (reviewed in [30]). 

Isoleucine, phenylalanine, t5nrosine, tryptophan Alanine, serine, glycine, cysteine, aspartic add, asparagine, glutamic acid, glutamine, arginine, histidine, valine, threonine, methionine, praline... 

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. 

Protein is an essential nutrient for human growth, development, and homeostasis. The nutritive value of dietary proteins depends on its amino acid composition and digestibility. Dietary proteins supply essential amino acids, which are not synthesized in the body. Nonessential amino acids can be synthesized from appropriate precursor substances (Chapter 17). In human adults, essential amino acids are valine, leucine, isoleucine, lysine, methionine, phenylalanine, tryptophan, and threonine. Histidine (and possibly arginine) appears to also be required for support of normal growth in children. In the absence from the diet of an essential amino acid, cellular protein synthesis does not occur. The diet must contain these amino acids in the proper proportions. Thus, quality and quantity of dietary protein consumption and adequate intake of energy (carbohydrates and lipids) are essential. Protein constitutes about 10-15% of the average total energy intake. 

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