Aleurone protein, wheat

It is now supposed that gibberellic acid stimulates the hormonal production of a-amylase (and, probably, of /9-amylase and others) in the aleurone layer surrounding the endosperm starch-reserve. Gibberellic acid released 400 mg. equivalents of D-glucose per g. in 90 hours in wheat grains, with a maximum hydrolytic activity after 60 hours. The effect on /9-amylase was thought to be a release (to the extent of 85%) from the protein-bound, insoluble form.876... 

Control of the synthesis of amylase ntRNA s in barley aleurone cells and the synthesis of cellulase mRNAs in pea epicotyl cells are similar in some respects. The control of cellulase activity in pea epicotyl is the only known example of auxin-induced formation of specific mRNA molecules. The formation of cellulase mRNA was demonstrated by the isolation of poly A + RNA s and in vitro synthesis of cellulase (71) using the protein-synthesizing system of wheat germ (72). The formation of cellulase mRNA precedes the increase in cellulase levels by more than 12 hr. Thus, it appears that the increase in rate of synthesis of translatable cellulase mRNA s in the pea epicotyl (71) and that of -amylase mRNA s in barley aleurone cells (65,... 

Many experiments have demonstrated the capacity of cellulases and of mixtures of cellulases, pectinases, and hemicellulases to break down or to soften plant cell walls. For human diets this would be beneficial in preparing infant or geriatric foods where reduced fiber content is desired. Recently treatment of wheat bran was found to increase the in vitro protein digestibility by 35% (63) and to increase weight gain of rats fed a bran-containing ration. The aleurone cell wall was the primary substrate for these enzymes. 

Eujita N, Taira T. A 56-kDa protein is a novel granule-bound starch synthase existing in the pericarps, aleurone layers, and embryos of immature seed in diploid wheat (Triticum monococcum L.). Planta 1998 207 125-132. 

Figure 7.1 Chemical images of the same wheat kernel cross-section showing the population on the z-axis. (a) Lipid in the scutellum and aleurone cell walls (b) Protein in the embryonic axis and aleurone cells ...

A range of methods have been described in the literature, and we shall consider them in the following order (1) the methods developed at the Food Research Institute-Norwich (FRIN), to isolate cell walls from a range of vegetables and fruits (runner beans, potatoes, cabbage and apples), cereals (oats, wheat and rye) and cereal products (wheat bran and rye biscuits), and lignified tissues (parchment layers of runner bean pods) (2) the special techniques, which may include wet sieving steps, used for the isolation of cell walls from potatoes, wheat endosperm, and wheat and barley aleurone layers (3) alternative methods for the isolation of cell walls from starch and protein-rich products (rice) and (4) methods used for the isolation of cell walls from suspension-cultured tissues. 

Spencer, D. and Higgins, T.J.V. Seed maturation and deposition of storage proteins. In Smith, H. and Grierson, D. (Eds.), The Molecular Biology of Plant Development, Blackwell, Oxford, U.K., 1982. Stevens, D.J. Reaction of wheat proteins with sulphite. III. Measurement of labile and reactive disulphide bonds in gliadin and in the protein of aleurone cells. J. Sci. FoodAgric. 24 279-283, 1973. 

Conventional hormone-binding studies have led to the discovery of GA-binding proteins in the cytosol of cucumber hypocotyls and pea epicotyls. These proteins have been partially purified and display some of the characteristics expected of a receptor [11, 12, 18, 17, 14]. In vivo and in vitro GA-binding studies have been performed with aleurones of barley and wheat [ 10,8] but, at present, no GA-binding proteins have been characterised, nor has a candidate GA-receptor emerged. 

When we look at the amino acid compositions of the proteins from starchy endosperm and aleurone layers (Sect. 2.1.2) we can get some indication as to how the different kinds of protein are distributed within the kernel (Table 2.6). In wheat, the aleurone layer protein is clearly different from that in the remainder of the endosperm, being extremely rich in arginine this could reflect a high globulin level. Rice aleurone grains, however, are rich in albumins [69]. 

Table 2.6. Amino acid composition of protein from starchy endosperm and aleurone grains of wheat cv. Manitoba...

A phytase has been isolated from the protein bodies of whole, milled, ungerminated barley, and this enzyme appears to be associated with the protein bodies of the aleurone layer (aleurone grains), a known storage site of phytin [141]. There is strong evidence (e.g. in wheat and rice) against the association... 

In the works of A. Konarev (Konarev et al. 1999 Konarev et al., 2004) shows in detail the variability of inhibitors of trypsin-like proteinases in cereals due to resistance to various grain pests. So in wheat trypsin inhibitors are represented by several genetically independent systems of proteins controlled by the genome and B chromosomes ID (endosperm), 3Dp (aleurone layer), IDS and 3Ap (leaf). Trypsin inhibitors of rye are controlled chromosome 3R and barley 3H. The most complex structure of inhibitors was wheat leaves, with the genomic formula AABBDD. In general, it is the sum of the spectra of trypsin inhibitors from several tetraploid (T. turgidum) (AABB) and (Aegilops tauschii Coss.) (DD) (Konarev, 1986 Konarev et al., 2004). 

Most pasta products are produced from sanolina mixed with small quantities of salt and, in some instances, with egg products. Thus, the chemical composition of pasta is practically equal to semolina. In order to produce semolina, durum wheat is milled, and the pericarp, germ, and aleurone layer are removed (Chapter 7). Therefore, the refined milled product is practically devoid of fiber and fat, and is rich in starch (>75%) and protein (11%-13%). Fresh eggs or egg solids are used to manufacture some pasta and noodles in order to improve flavor, texture, and color. The use of egg upgrades protein content and quality, and also supplies phospholipids and essential vitamins and minerals. Table 17.13 depicts the chemical compositions of pasta products before and after cooking. 

Shorts Name of the wheat milled fractions rich in germ, aleurone, and leftover starch obtained at the end of the roll milling process. Shorts contain more protein and fat than bran and are usually retained by the U.S. No. 60 sieve. 

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