Barley amino acids

LPC Product Quality. Table 10 gives approximate analyses of several LPC products. Amino acid analyses of LPC products have been pubhshed including those from alfalfa, wheat leaf, barley, and lupin (101) soybean, sugar beet, and tobacco (102) Pro-Xan LPC products (100,103) and for a variety of other crop plants (104,105). The composition of LPCs varies widely depending on the raw materials and processes used. Amino acid profiles are generally satisfactory except for low sulfur amino acid contents, ie, cystine and methionine. 

Diffusion-mediated release of root exudates is likely to be affected by root zone temperature due to temperature-dependent changes in the speed of diffusion processes and modifications of membrane permeability (259,260). This might explain the stimulation of root exudation in tomato and clover at high temperatures, reported by Rovira (261), and also the increase in exudation of. sugars and amino acids in maize, cucumber, and strawberry exposed to low-temperature treatments (5-10°C), which was mainly attributed to a disturbance in membrane permeability (259,262). A decrease of exudation rates at low temperatures may be predicted for exudation processes that depend on metabolic energy. This assumption is supported by the continuous decrease of phytosiderophore release in Fe-deficient barley by decreasing the temperature from 30 to 5°C (67). 

Plant defensins are cystine-rich, cationic peptides ranging in size from 45 to 54 amino acids, of which eight are cysteine. They were first discovered in wheat and barley ° and were proposed to form a novel subclass of thionins, the 7-thionins. As it became clear that they closely resemble mammalian and insect defensins in primary and secondary structure, the term plant defensins was introduced to describe these peptides. It is generally assumed that all plants express plant defensins " and that they are expressed in a wide range of plant tissue, that is, leaves, floral tissue,tubers,bark, root, pods, and seeds,with seeds in particular being from where most plant defensins have been isolated. ... 

Only proteins that contain proline bind polyphenols. Asano et al. (1982) demonstrated that the haze-forming activity of a protein is roughly proportional to the mole percentage of proline it contains (see Fig. 2.3). DNA has codes for exactly 20 amino acids. If each of these were equally present in a protein, there would be 5 mol% of each one. In fact, most proteins have much less proline than this. There are a few exceptions. Casein has about 8 mol% proline and the grain prolamins (proline-rich, alcohol-soluble proteins) are even higher. Hordein, the barley prolamin, contains about 20 mol% proline. As a result, it readily forms haze with polyphenols and is the main beer haze-active (HA) protein. Hordein contains even more glutamine (Q) than proline (P), and often these amino acids are adjacent in the protein (see Fig. 2.4). In fact, the sequence P-Q-Q-P occurs... 

FIGURE 2.4 Partial amino acid sequence of barley hordein (source of haze-active protein in beer) P = proline and Q = glutamine. 

Wheat, rye, and barley have a common ancestral origin in the grass family. Oats are more distantly related to the analogous proteins in wheat, rye, and barley and the oat prolamins (avenin) have substantially lower proline content. Avenin accounts for 5-15% of the total protein in oats, whereas in wheat, barley, and rye, prolamins constitute 40-50% of the total protein (Kilmartin et al., 2006). Some investigators believe that there are similarities between the protein structure of oats and some wheat-like sequences, which may indicate that large amounts of oats could potentially be toxic to patients with celiac disease. However, the putative toxic amino acid sequences are less frequent in avenin than in other prolamins, which explains the less toxic nature of oats (Arentz-Hansen et al., 2004 Ellis and Ciclitira, 2001, 2008 Shan et al., 2005 Vader et al., 2002, 2003). 

Barley protein, moisture, lysine, amino acid, (i-glucan... 

Reduced nitrogen retention was reported when chicks were fed rye diets (18). Supplementation of those diets with amino acids increased the retention of only the supplemented amino acids and not those contributed by the rye. These observations are compatible with the trypsin inhibitor hypothesis of other researchers (9,10). On the other hand, examination of the differences between endosperm and embryo and trypsin inhibitors of barley, wheat, and rye has revealed that, in contrast to certain trypsin inhibitors from leguminous seeds, those from the cereal grains appeared to be relatively weak, nonstoichiometric inhibitors of trypsin (19). 

Subsequently, two cDNA clones encoding barley BEIIa and BEIIb were isolated.263 The major structural difference between the two enzymes was the presence of a 94-amino acid N-terminal extension in the BEIIb precursor. 

X-ray crystallographic study of barley malt a-amylase has shown that it also has three domains in which the largest domain, domain A, also has a ((3/a)8-barrel structure, composed of amino acid residues 1 to 88 and 153 to 350.122 Domain B is composed of 64 residues (88 to 152) that are an excursion from the third (3-strand and the third a-helix, similar to the structure of porcine pancreatic a-amylase. Domain C occurs at the C-terminus and is composed of 53 residues (351 to 403) that are arranged into a five-strand (3-sheet. 

In the brewing industry, there is a development toward substitution of malt with unmalted barley and amylase, by use of glu-canase and protease of microbial origin. The neutral protease from Bacillus amyloliquefaciens and the thermostable neutral protease Bacillus subtilis var. thermoproteolyticus have been used by brewers successfully to hydrolyze barley proteins into amino acids and peptides. 

The complete deduced amino-acid sequences of the open reading frames of the Waxy genes from maize and barley are known. About 75% identity can be seen in the sequence with respect to amino acids. If functionally similar amino acids are considered, then the homology is about 81%. Thus, these two proteins are similar in sequence and probably carry out the same function in the starch granule. There is, however, very little sequence homology with the bacterial glycogen synthase beyond the N-terminal sequence. 

Plantacyanin is represented in the Arabidopsis genome by a single gene, while rice has nine. Multiple plantacyanin sequences can also be identified in plant species such as wheat, barley, and maize. Spinach plantacyanin is 91-amino acids long and is perhaps the smallest blue copper protein known. 

The existence of sulfite oxidase in plants snch as Arabidopsis thaliana (wall or thule cress), tobacco, pea, spinach, barley, carrot, and poplar trees has now been confirmed, and the enzyme from A. thaliana has been structurally characterized. The homodimeric, peroxisomal enzyme lacks the heme domain observed in animal sulfite oxidases, making it the simplest Mo-MPT enzyme yet isolated from eukarya. The animal and plant sulfite oxidases have an overall 47% sequence identity. The detoxification of sulfite, produced in the assimilation of sulfate into sulfur-containing amino acids and membrane components (sulfatides) and from environmental sources (acid rain), is also the principal role of the plant enzymes. 

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