Nutritionally essential amino acids

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

Humans can synthesize 12 of the 20 common amino acids from the amphiboHc intermediates of glycolysis and of the citric acid cycle (Table 28-1). While nutritionally nonessenrial, these 12 amino acids are not nonessential. AH 20 amino acids are biologically essential. Of the 12 nutritionally nonessential amino acids, nine are formed from amphibolic intermediates and three (cysteine, tyrosine and hydroxylysine) from nutritionally essential amino acids. Identification of the twelve amino acids that humans can synthesize rested primarily on data derived from feeding diets in which purified amino acids replaced protein. This chapter considers only the biosynthesis of the twelve amino acids that are synthesized in human tissues, not the other eight that are synthesized by plants. 

Cysteine, tyrosine, and hydroxylysine are formed from nutritionally essential amino acids. Serine provides the carbon skeleton and homocysteine the sulfur for cysteine biosynthesis. Phenylalanine hydroxylase converts phenylalanine to tyrosine. 

List the nutritionally essential amino acids for human beings. Compare these needs with those of other species, including lactic acid bacteria, malaria parasites, green plants, etc. 

Another bacterium that contributes to commensal biofilms is Eikenella corrodens, a gram negative, small rod (Fig. 13.2c). E. corrodens grows in a healthy oral cavity by reducing nitrate in saliva to nitrite (Sects. 1.3.2 and 12.1.3). It is an important contributor to bite wound infections and is also the major known producer of lysine decarboxylase, which converts lysine to cadaverine and carbon dioxide (Fig. 13.4). Lysine is a nutritionally essential amino acid, whereas cadaverine is not. In humans, E. corrodens and lysine... 

Methionine—The 1-isomer is a nutritionally essential amino acid and the most important natural source of active methyl groups in the body, hence usually involved in methylations in vivo. 

Valine is unique among the nutritionally essential amino acids in that its deficiency in the rat causes, in addition to loss of appetite and stunted growth, a syndrome in which the animal becomes extremely sensitive to touch and displays a severe incoordination of movement. ... 

Gelatin can be a source of essential amino acids when used as a diet supplement and therapeutic agent. As such, it has been widely used in muscular disorders, peptic ulcers, and infant feeding, and to spur nail growth. Gelatin is not a complete protein for mammalian nutrition, however, since it is lacking in the essential amino acid tryptophan [73-22-3] and is deficient in sulfur-containing amino acids. 

Amino acids are important components of the elementary nutrients of living organisms. For humans, ten amino acids are essential for existence and must be iagested ia food. The nutritional value of proteias is governed by the quantitative and qualitative balance of iadividual essential amino acids. ... 

The nutritional value of a proteia can be improved by the addition of amino acids of low abundance ia that proteia. Thus the fortification of plant proteias such as wheat, com, and soybean with L-lysiae, DL-methionine, or other essential amino acids (L-tryptophan and L-threonine) is expected to alleviate some food problems (11). Such fortification has been widespread ia the feedstuff of domestic animals. 

E. coli can easily grow on corn steep liquor with phosphate buffer for an incubation period of 3 days. Lysine is an essential amino acid for the nutrition of humans, which is used as a... 

Historically, the development of animal cell culture systems has been dependent upon the development of new types of tissue culture media. Mouse L cells and HeLa cells were developed using a balanced salt solution supplemented with blood plasma, an embryonic tissue extract, and/or serum. In 1955 Eagle developed a nutritionally defined medium, containing all of the essential amino acids, vitamins, cofactors, carbohydrates, salts, and small amounts of dialyzed serum (Table 1). He demonstrated that this minimal essential medium (MEM) supported the long-term growth of mouse L and HeLa ceils. Eagle s MEM was so well defined that the omission of a single essential nutrient eventually resulted in the death of these animal cells in culture. 

The importance of the basal medium in culturing normal cells was demonstrated by Dr. Richard Ham (Ham and McKeehan, 1979). Dr. Ham s laboratory developed a number of different types of culture media, in which the concentrations of the individual nutritional components have been optimized to support the growth of specific types of normal, differentiated cells. The most widely used is nutrient mixture FI2, which contains nonessential, as well as essential, amino acids, a number of lipids, and trace elements (Table 5). 

Commonly administered LVPs include such products as Lactated Ringers Injection USP, Sodium Chloride Injection USP (0.9%), which replenish fluids and electrolytes, and Dextrose Injection USP (5%), which provides fluid plus nutrition (calories), or various combinations of dextrose and saline. In addition, numerous other nutrient and ionic solutions are available for clinical use, the most popular of which are solutions of essential amino acids or lipid emulsions. These solutions are modified to be hypertonic, isotonic, or hypotonic to aid in maintaining both fluid, nutritional, and electrolyte balance in a particular patient according to need. Indwelling needles or catheters are required in LVP administration. Care must be taken to avoid local or systemic infections or thrombophlebitis owing to faulty injection or administration technique. 

A specific example of the law of the minimum on a molecular level is the essential amino acids. The need for essential amino acids in human nutrition shows that one amino acid cannot substitute for another. Substitution of one amino acid for another can lead to disease. This is shown, for example, in sickle... 

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. 

The diet must provide those amino acids which the body cannot synthesize (essential amino acids, EAA) and nitrogen in the form of nonessential amino acids (NEA). Both EAA and NEA are required for biosynthesis of proteins and other nitrogen-containing compounds necessary for homeostasis or growth. Thus, the total nitrogen content of a specific food must be considered to be nutritionally significant. 

In recent years, a number of workers have published amino acid analyses of the sweet potato (38, 43, 35, 22, 18). The overall picture is that the sweet potato amino acid pattern is of good nutritional quality but that the variability of individual amino acids both within the same cultivar and across cultivars is very high. For example, Walter et al. (44) reported that with the exception of aromatic amino acids, every essential amino acid has a score of less than 100 in one or more cultivars. The amino acid score is defined as the g of amino acid in 100 g of test protein divided by the number of g of that amino acid in the FAO/WHO reference pattern times 100. Bradbury et al. (22) showed that, for the same cultivar, environmental effects on the amino acid patterns is significant. For three cultivars, they found a mean percent standard deviation for all amino acids of 24.2,... 

From amino acid compositions, evaluations o7" the nutritional potentials of cucurbit meals and globulins can be calculated according to FA0/WH0 (54). The A E ratios, which are the amounts of each essential amino acid relative to the total amount of essential amino acids, are shown in Table II. These data indicate that, like most other oilseeds, cucurbit seeds are deficient in lysine and sulfur-containing amino acids. However, sulfur-containing amino acids are considerably high in CitrullI us colocynthis (egusi, ancestral watermelon) seed protein and exceed the suggested level in FA0/WH0 reference protein (55). 

A protein that is unduT7 rich in the ten essential amino acids would not provide sufficient nitrogen for other metabolic processes without obligatory catabolism of the essential amino acids. Thus, the proportion of the total nitrogen intake that essential amino acids form indicate how a given protein fulfills nutritional requirements for proteins. This proportion, the E/T ratio (54), indicative of the amount of protein nitrogen supplied by essential amino acids, is (in g of essential amino acids per g of nitrogen)... 

By the 1930s many workers had shown that nutritionally inadequate proteins, such as zein from maize, could be effective as a source of nitrogen if supplemented by additional amino acids (for zein, tryptophan). Even if it contained all the essential amino acids, the amount of protein in the diet influenced the results. Osbome and Mendel found that if the diet contained 18% by weight casein, which is low in cystine, young rats grew, but if the amount of protein was diminished, added cystine was required to offset the relative deficiency of this amino acid. Later, after methionine had been discovered, it was shown to replace the need for cystine. 

Another interesting possibility presents itself in this connection. We have assumed all along, tentatively at least, that all individuals within the same species have qualitatively the same nutritional needs. This, in effect, may not be true, as we have hinted in connection with our discussion of amino acid needs. It is within the realm of possibility and even probability that certain amino acids, e g., glutamic acid, glutamine, or arginine, may be "essential amino acids" for certain individuals in the sense that they are essential for health... 

Finally, they may be classified on the basis of whether they are nonessential, essential (exogenous), and conditionally essential amino acids. Food and tissue proteins contain 20 amino acids of nutritional importance. Nine of these amino acids (histidine (His), He, Leu, Lys, methionine (Met), Phe, Thr, Trp, and Val) cannot be synthesized by the body and they are therefore essential or indispensable nutrients that must be... 

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