Dietary sources of amino acids

Nutritional significance. As one of the major whey proteins in human milk and also relatively abundant in bovine colostrum, LF is of interest as a dietary source of amino acids as well as for the bioavailability of iron. LF has an... 

Plants and many microorganisms are able to synthesise proteins from simple nitrogenous compounds such as nitrates. Animals cannot synthesise the amino group, and in order to build up body proteins they must have a dietary source of amino acids. Certain amino acids can be produced from others by a process known as transamination (see Chapter 9), but the carbon skeletons of a number of amino acids cannot be synthesised in the animal body these are referred to as essential or indispensible amino acids. 

Proteins.— The nitrogenous food materials make up 10-16 per cent, of the solids of the human diet, and may reach 30 per cent, if the consumer can afford them. They are the most expensive and most palatable part of the dietary, and are well represented in eggs, meat, fowl, fish, milk, cheese, nuts, cereals, and legumes (beans, peas, lentils). Proteins form the only dietary source of amino acids, the content of which differs in different proteins. For this reason, it is generally believed that about half of the food protein should be derived from animal sources to ensure getting a sufficient supply of the correct amino acids, and several sorts of protein are included in the dietary so as to provide an adequate selection. 

The term protein usually refers to crude protein (CP measured as N content x 6.25) in requirement tables. Protein is required in the diet as a source of amino acids (AAs), which can be regarded as the building blocks for the formation of skin, muscle tissue, feathers, eggs, etc. Body proteins are in a dynamic state with synthesis and degradation occurring continuously therefore, a constant, adequate intake of dietary AAs is required. An inadequate intake of dietary protein (AAs) results in a reduction or cessation of growth or productivity and an interference with essential body functions. 

Dietary protein is a vital source of amino acids. Proteins ingested in the diet are digested into amino acids or small peptides that can be absorbed by the intestine and transported in the blood. Another source of amino acids is the degradation of defective or unneeded cellular proteins. 

Dietary proteins are a source of amino acids which can serve as important precursors for gluconeogenesis. During a fast or starvation, a major contribution is made by alanine which is released along with other amino acids from skeletal muscle. Since labile proteins rich in alanine are not present in muscle, the released alanine appears to result from the activity of alanine aminotransferase (Section 16.1) which produces alanine from pyruvate. This is the basis of the alanine cycle which also operates between skeletal muscle and the liver. The alanine cycle functions only when peripheral tissues reoxidize glycolytic NADH through the oxidative phosphorylation pathway. In the presence of oxygen, pyruvate is not utilized in lactate production and is available for the amino transfer reaction. 

The metabolic machinery of all animals must be provided with water, amino acids, energy, minerals and viteunins. In ruminemts, utlliz d le nutrients are provided by a combination of dietary sources plus those synthesized by rumen bacteria emd protozoa and until recently little attention has been directed towards dietary supplies of amino acids and B-conplex vitamins. However, information accrued during the last decade demonstrates that ruminal outflows of these nutrients is not always sufficient for high rates of productivity (2. 1.) ... 

While the dog is a carnivore, it is able to adapt to an omnivorous diet. Requirements for dietary sources of energy, amino acids, glucose precursors, fatty acids, minerals, vitamins, and water have been established based on recommendations by the National Research Council (NRC, 1985). Adult beagles maintained in a laboratory environment function well with one feeding of standard laboratory chow per day. In safety assessment testing, however, some compounds may induce serious dietary deficiencies through induced loss of appetite, malabsorption, or vomiting, and, in these cases, it may be advisable to provide a dietary supplement. 

All human tissues are capable of synthesizing the nonessential amino acids, amino acid remodelling and conversion of non-amino-acid carbon skeletons into amino acids and other derivatives that contain nitrogen. However, the liver is the major site of metabolism of nitrogenous compounds in the body. Dietary proteins are the primary source of essential amino acids (or nitrogen). Digestion of dietary proteins produces amino acids, which are absorbed through epithelial cells and enter the blood. Various cells take up these amino acids that enter the cellular pools. 

Dietary purines are not an important source of uric acid. Quantitatively important amounts of purine are formed from amino acids, formate, and carbon dioxide in the body. Those purine ribonucleotides not incorporated into nucleic acids and derived from nucleic acid degradation are converted to xanthine or hypoxanthine and oxidized to uric acid (Figure 36-7). Allopurinol inhibits this last step, resulting in a fall in the plasma urate level and a decrease in the size of the urate pool. The more soluble xanthine and hypoxanthine are increased. 

E. In the presence of adequate dietary sources of tyrosine, phenylalanine is not an essential amino acid. 

Reduced nitrogen enters the human body as dietary free amino acids, protein, and the ammonia produced by intestinal tract bacteria. Amino acids derived from dietary proteins are the main source of amino groups. In which metabolic circumstances, amino acids in body can undergo oxidative degradation ... 

The properties of other proteins — such as soybean protein, egg protein, and meat protein — as well as their food sources (matrices), are major topics in food science leather than dwell on this subject, we will turn to some of the features of dietary protein, after digestion and acquisition of their component amino acids by the body. The role of dietary protein in allowing growth and the maintenance of health will be detailed, though the biochemical machinery (ribosomes, tRNAs, aminoacyl tRN A synthases) used for the assembly of amino acids into proteins will not be described. 

Date pulp is low in fat and protein but rich in sugars, mainly fructose and glucose, making it a potent source of caloric energy. It contains excellent amounts of amino acids for protein dietary minerals such as selenium, potassium, calcium, magnesium, manganese, and iron several B vitamins vitamin C omega fatty acids phytosterols and both insoluble and prebi-... 

Protein turnover is not completely efficient in the reutilization of amino acids. Some are lost by oxidative catabolism, while others are used in synthesis of non-protein metabolites. For this reason, a dietary source of protein is needed to maintain adequate synthesis of protein. During periods of growth, pregnancy, lactation, or recovery from illness, supplemental dietary protein is required. These processes are affected by energy supply and hormonal factors. An overview of amino acid metabolism is presented in Figure 17-1. 

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