Barley amino acid content

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. 

TABLE 1.2 Comparison of essential amino acids content of barley, corn and wheat to FAO/WHO suggested requirement... 

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). 

Table 13.1 Contents of essential amino acid in grain of wheat, rye and barley compared with the WHO recommended levels (FAO, 1973).

The PSI-C polypeptide has a molecular mass of 9 kDa and binds the iron-sulfur clusters A and B (4). The first proposal of the PSI-C polypeptide as being an iron-sulfur protein was based on its high cysteine content (37). The protein was isolated from PS I particles of barley and shown to carry zero-valence sulfur which is indicative for a denatured iron-sulfur center (4). The amount of zero-valence sulfur bound to the polypeptide corresponded to 8 acid-labile sulfides per molecule (4). The N-terminal amino acid sequence of the isolated protein permitted the identification of its corresponding chloroplast gene which... 

Prolamines a group of simple (unconjugated) proteins, soluble in 90% ethanol. They occur in cereals, and contain up to 15 % proline and 30-45 % glutamic add, but they have only low contents of essential amino acids. The chief representatives are gliadin (wheat and rye), zein (maize contains no tryptophan or lysine) and hordein (barley contains no lysine). Oats and rice do not contain P. 

Pig and poultry diets based on cereals and vegetable protein sources are now routinely supplemented with L-lysine hydrochloride (supplying 780 g lysine/kg), dl-methionine and L-threonine. A diet for a finishing pig, which has to contain 10 g lysine/kg, required a combination of 750 g barley and 250 g soya bean meal/kg, and this mix has a crude protein content of 185 g/kg (see Appendix 2, Table A.2.2.2). With the inclusion of 2 g of lysine hydrochloride, the same lysine content can be achieved with a mix of 808 g barley and 190 g soya bean meal, and the protein content is reduced to 165 g/kg. Such reductions in crude protein content have maintained a balanced supply of amino acids and resulted in improved rates of liveweight gain and food conversion efficiency. It is important that the supplementary acids are not used excessively to satisfy the animal s requirements, since this may bring about an undersupply of other essential amino acids. 

Thr-Glu-Ala-Ala-Lys-Gln-Lys-Ala-Ala-Glu-Thr. A similar sequence has been observed in one of the ABA-induced proteins in cotton embryogenesis (Lea 7) [1]. ABA-induced proteins with a repeating sequence and unusually high content of specific amino acids have been observed in several plant systems [ 1,5,16]. In barley aleurone layers, pHV Al as well as several other ABA-induced proteins can be induced by osmotic or salt stress (LS Lin and THD Ho, unpublished observation). At least in osmotic stress, the level of ABA is increased, and the osmotic stress induction of ABA proteins is prevented by an ABA biosynthesis inhibitor, fluridone. Thus, the stress-induction of these proteins is most likely the consequence of stress-induced synthesis of ABA. 

Fig. 6.15A and B. Changes in the contents of selected amino acids in the non-protein fractions of (A) barley endosperm and (B) embryo, o—o amide nitrogen a—a glutamic acid a—a proline ------- arginine. Based on Folkes and Yemm, 1958 [51]... 

The proteins of different cereal flours vary in their amino acid composition (Table 15.10). Lysine content is low in all cereals. Methionine is also low, particularly in wheat, rye, barley, oats and corn. Both amino acids are significantly lower in flour than in muscle, egg or milk proteins. By breeding, attempts are being made to improve the content of all essential amino acids. This approach has been successful in the case of high-lysine barley and several corn cultivars. 

The nature of the active site in beta-amylase is not unambiguously known for enzymes from different sources. Early experiments on purified barley and on malted barley first indicated, from studies of the modification of the enzyme with nitrous acid and ketene, that free tyrosine and sulfhydryl groups are essential for activity, whereas free a-amino groups are not. The importance of the sulfhydryl groups was emphasized by the partial recovery of activity of the modified or oxidized enzyme (that is, treated with nitrous acid, iodine, phenyl mercuribenzoate, ferricyanide, and cupric ions) when it was treated with hydrogen sulfide or cysteine. Barley feeto-amylase (not highly purified) has been reported to contain 12—15 sulfhydryl groups per molecule by titration with p-chloromercuribenzoate, and the loss of free sulfhydryl content by treatment with L-ascorbic acid in the presence of cupric ions was found to be directly related to the loss of activity. 

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