Nonprotein nitrogen

Acetamide has been used experimentally as a source of nonprotein nitrogen for sheep and dairy cattie (13). It does not appear to be toxic in amounts of about 2—3% of ration. Buffering the diet with dibasic acids serves to allow higher levels of intake because the ammonia Hberated in the digestive process is then scavenged. 

Crude protein = %nitrogen X 6.25. Does not accurately reflect true protein content. Algal cells may contain nonprotein nitrogen substances, eg, 4—6% nucleic acids, dry wt basis. 

Azetidine-2-carboxylic acid, the lower homolog of proline, has been isolated from Convallaria majalis (lily of the valley) 40,44), Polygonatum officinalis (Solomon s seal) 153), and Polygonatum multiflorum 45). Fowden and Steward 47) surveyed plants from 56 genera for nitrogenous compounds and found azetidine-2 -carboxylic acid to be restricted to members of the Liliaceae. In some species it was identified in leaf, stem, and root but was more commonly found in the seed. In Polygonatum, azetidine-2-carboxylic acid accounted for 75% or more of the total nonprotein nitrogen in the rhizome 45). There was no evidence that it occurred as a constituent of protein. 

Figure 20, Demonstration of disparity between nonprotein nitrogen and urea levels in a patient with terminal kidney disease complicated by liver involvement...

Nonprobability sampling, 26 1001 Nonproduct contact utilities, 11 45-46 Nonprotein amino acids, 2 554 Nonprotein nitrogen (NPN), 10 865 Nonquenching photoluminescence properties, 26 804-805... 

For those sweet potato cultivars studied, the crude protein (N x 6.25) contains both protein and nonprotein nitrogen (NPN). 

Because yams are poor sources of dietary nitrogen, a knowledge of nonprotein nitrogen metabolism in yams would provide useful information for retaining the amount present in fresh tubers and preventing the usual losses suffered during storage in... 

The basic material in seeds that is extractable with trichloroacetic acid solutions is ascribed to nonprotein nitrogen when the acid is in the 0.4-1.0 M concentration range. Gel electrophoresis on a sodium dodecylsulfate polyacrylamide medium pointed to the presence of 12 kDa polypeptides in soybean meal and 7, 10, 12 and 28 kDa in almond meal332. 

Dierick, N., Vandekerckhove, P. and Dameyer, D. (1974). Changes in nonprotein nitrogen compounds during dry sausage ripening, J. Food Sci., 39, 301. 

MacdowalP found that tobacco leaves were most susceptible to injury by ozone (at 0.035 ppm for 5 h) just after full leaf expansion. This point corresponded to the banning of the decline in protein content. Lee modified the nitn en content of tobacco leaves by supplying urea and found a positive correlation of injury caused by ozone (at 1 ppm for 5 h) with nonprotein nitrogen, but not with protein. This result is in contrast with that of Ting and Mukeiji, who found that, in cotton leaves (in which the period of maximal susceptibility was at about 75% of full leaf expansion), the amino acid pool was low at the time of maximal susceptibility. However, ozone treatment (0.7 ppm for 1 h) increased the free amino acid pool. 

A large number of N-containing compounds of low molecular weight are not precipitated with proteins by 12% trichloroacetic acid. Some small peptides are included in this group. These nonprotein nitrogen (NPN) constituents aggregate about 1 g/liter and account for about 6% of the total N (i.e., 250-350 mg of N per liter). The principal NPN components are listed in Table 1.6 (Wolfschoon-Pombo and Kloster-meyer 1981). The wide variations in concentrations that have been reported for these constituents probably arise from the fact that many of them are metabolites of amino acids and nucleic acids and from the fact that their concentrations in milk depend on the amounts of those substances consumed by the cow. 

Lactosylurea. Lactosylurea is formed under acid conditions from lactose and urea (McAllan et al 1975) conversion of 75% of the lactose was achieved. Widell (1979) described a method for its preparation from whey and urea intended for feeding to ruminants. Ruminants can utilize nonprotein nitrogen compounds for protein synthesis, but urea itself can cause difficulties through too rapid decomposition to ammonia by the rumen enzymes. Lactosylurea appears to meet the requirements for satisfactory palatability, controlled nonprotein nitrogen release, and low toxicity. 

The relationship between pH, mineral retention, and basic cheese structure has been illustrated by Lawrence et aL (1984). Hill et al. (1985) have developed mathematical models of the association between pH at draining and mineral content of whey. The calcium, phosphorus, magnesium, and nonprotein nitrogen content of whey increased with decreasing pH, while sodium and potassium levels were not affected. Mineral and nonprotein nitrogen concentrations in the whey were not associated with cooking temperature. 

Penicillium caseicolum produces an extracellular aspartyl proteinase and a metalloproteinase with properties very similar to those of the extracellular enzymes produced by P roqueforti (Trieu-Cout and Gripon 1981 Trieu-Cout et al. 1982). Breakdown of casein in mold-ripened cheese results from the synergistic action of rennet and the proteases of lactic streptococci and penicillia (Desmazeaud and Gripon 1977). Peptidases of both lactic acid bacteria and penicillia contribute to formation of free amino acid and nonprotein nitrogen (Gripon et al. 1977). 

The presence of protein, albumin, and acetone in the urine and increases in blood levels of urea nitrogen, nonprotein nitrogen, and creatinine have been observed in individuals acutely ingesting rat (or roach) poisons or fireworks containing white phosphorus (Dathe and Nathan 1946 Diaz-Rivera et al. 1950 Dwyer and Helwig 1925 Fletcher and Galambos 1963 Matsumoto et al. 1972 McCarron et al. 1981 Newburger et al. 1948 Pietras et al. 1968 Rao... 

Urea nitrogen Nonprotein nitrogen Uric acid... 

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