Cereal amino acids

H. Martens, Factor analysis of chemical mixtnres. Non-negative factor solutions for cereal amino acid data, Anal. Chim. Acta, 112, 423-141 (1979). 

Martens, H., Factor Analysis of Chemical Mixtures Non-Negative Factor Solutions for Cereal Amino Acid Data Anal. Chim. Acta 1979, 112, 423—141. 

Since dietary cereals are low in sulfur-containing amino acids, they produce an alkaline urine which favors the retention of bone minerals. In post-menopausal women, there appears to be some interaction between the diet and the effect produced by estrogens on bone mineral content (28). 

Plant proteins from single sources, such as soybean meal, may be abundant in specific amino acids that are deficient in some cereal grains. Thus a combination of soybean meal and com with theh amino acid symbiosis may provide an exceUent amino acid profile for dogs. Plant protein mixtures alone do not meet the amino acid needs for cats, because taurine [107-35-7] is not generaUy present in plant proteins. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

For us to remain perfectly healthy, the protein in our diet must supply suffident quantities of amino acids. We prefer to eat our protein in particular forms, that is in foods having particular textures, tastes and smells (these are called organoleptic properties). Conventional sources of protein are plants, mainly as cereals and pulses, and animals, mainly as meat, eggs and milk. The proportions of such proteins eaten in various parts of the world differ widely (Figure 4.1). 

Niacin was discovered as a nutrient during studies of pellagra. It is not strictly a vitamin since it can be synthesized in the body from the essential amino acid tryptophan. Two compounds, nicotinic acid and nicotinamide, have the biologic activity of niacin its metabolic function is as the nicotinamide ring of the coenzymes NAD and NADP in oxidation-reduction reactions (Figure 45-11). About 60 mg of tryptophan is equivalent to 1 mg of dietary niacin. The niacin content of foods is expressed as mg niacin equivalents = mg preformed niacin + 1/60 X mg tryptophan. Because most of the niacin in cereals is biologically unavailable, this is discounted. 

The grain or pulse forms of legumes have a high total protein content (20-26%) and can therefore be used as a natural supplement to cereals. Pulses are normally deficient in the essential amino acids methionine and cystine but contain enough lysine, whereas cereals are deficient in lysine but contain enough methionine and cystine. 

Proteins have been isolated from many cereal seeds that have extensive regions of repeating hexa- to nonapeptides. The consensus repeats are rich in Pro and Gin, and always contain an aromatic amino acid, generally Tyr. The CD spectra of fragments of these proteins containing the repeating sequence have been reported (DuPont etal., 2000 Gilbert... 

Characteristically, legume seeds are rich in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal diets. Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water solubility, water and fat binding and emulsification. Thus soybean flours, protein concentrates and isolates have been used widely as nutritional supplements and functional ingredients in foods. 

Vegetarians need to be aware of the amino acids present in their diet, since most animal proteins contain amino acids approximately in proportion to those required by humans but this is not true for all vegetable proteins. This problem is particularly severe for those dependent on a single source of plant protein, for example corn or rice, as is frequently the case in poorer parts of the world. In general, legumes are low in methionine while cereals are low in lysine. Some strains of com now contain lysine, but the best advice to vegetarians is to include as wide a variety of plants as possible in their diet (Chapter 15). 

Be (pyridoxine) Meats, cereals, lentils, nuts, some fruits and vegetables Amino acid metabolism... 

Selenium is present in meat, seafood and cereals. The former two contain the highest levels. It is present in soil as inorganic selenium that enters the food chain via plants. In plant protein, it is present as selenomethionine and in animals as selenocysteine this difference is due to the metabolism of selenomethionine in the liver as part of the normal catabolic pathway for methionine (Chapter 8). Somewhat surprisingly, selenocysteine is incorporated into protein via a specific tRNA which possesses a UCA anticodon for this amino acid. 

The nutritional value of proteins (see p. 360) is decisively dependent on their essential amino acid content. Vegetable proteins—e.g., those from cereals—are low in lysine and methionine, while animal proteins contain all the amino acids in balanced proportions. As mentioned earlier, however, there are also plants that provide high-value protein. These include the soy bean, one of the plants that is supplied with NH3 by symbiotic N2 fixers (A). 

Vitamins B6, B12, and folate An elevated plasma homocysteine level is associated with increased cardiovascular risk (see p. 263). Homocysteine, which is thought to be toxic to the vascular endothelium, is converted into harmless amino acids by the action of enzymes that require the B vitamins—folate, B6 (pyridoxine), and B12 (cobalamin). Ingesting foods rich in these vitamins can lower homocysteine levels and possibly decrease the risk of car diovascular disease. Folate and B6 are found in leafy green veg etables, whole grains, some fruits, and fortified breakfast cereals. B12 comes from animal food, for example, meat, fish, and eggs. 

Niacin is found in unrefined and enriched grains and cereal, milk, aid lean meats, especially liver. Limited quantities of niacin can also be obtained from the metabolism of tryptophan. [Note The pathway is inefficient in that only about 1 mg of nicotinic acid is formed from 60 mg of tryptophan. Further, tryptophan is metabolized to niacin orty when there is a relative abundance of the amino acid—that is, alter the needs for protein synthesis and energy production have been met]... 

Cold cereal is often fortified with all sorts of vitamins and minerals but is deficient in the amino acid lysine. How might this deficiency be compensated for in a breakfast meal ... 

L-Lysine. Hd io3 Fermentation (AM) First limiting amino acid for cereals... 

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