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Recent studies of nitrogen (N) cycling in arctic tundra have indicated that inorganic N supplied to plants by mineralization is not sufficient to meet the annual requirement of N by many tundra species. Whereas N mineralization is slow in tundra soils and concentrations of inorganic N are low, these soils have large stocks of both structural and soluble organic N. In light of these observations, kinetics of absorption of three amino acids (glycine, aspartic acid, and glutamic acid) were measured in dominant vascular plant species of the four major ecosystems types in arctic Alaska and compared with concentrations of free amino acids in soils. Absorption rates were measured on roots using ^1^4C-labeled substrates. Concentrations of free amino acids in soil were measured on water-extracted samples by high pressure liquid chromatography. All species had higher capacity (V\"m\"a\"x) for ammonium uptake (measured using methylamine as an ammonium analogue) than for any amino acid. However, at concentrations observed in the field, uptake rates estimated for amino acids were similar to (glycine) or less than (aspartic and glutamic acids) that for ammonium. On the basis of these comparisons, uptake rates of the three amino acids together may account for between 10 and 82% of the total N uptake in the field, depending on species and community. Deciduous shrubs had higher uptake rates than the more slowly growing evergreen shrubs, suggesting that new growth created a sink that strongly influenced capacity for amino acid uptake. In general, ectomycorrhizal species had higher amino acid uptake than did non-mycorrhizal species. In species that were sampled from more than one community, amino acid uptake rates were highest in the community where a given amino acid was most abundant in the soil. The results indicate that, in arctic tundra, plants short-circuit the mineralization step of decomposition by directly absorbing amino acids. This implies that in the organic soils of these tundra systems (1) inorganic nitrogen is an inadequate measure of plant-available soil nitrogen, (2) mineralization rates underestimate nitrogen supply rates to plants, (3) the large differences among species in capacities to absorb different forms of N provide ample basis for niche differentiation of what was previously considered a single resource, and (4) by short-circuiting N mineralization, plants accelerate N turnover and effectively exert greater control over N cycling than has been previously recognized.

The aim of this study was to examine the physicochemical properties and amino acid composition of rabbit meat after the enrichment of rabbit diet with oregano, sage, and Eleutherococcus senticosus extracts, and to make a comparison with the commercial product XTRACT and control samples. The addition of oregano and sage extracts as well as El. senticosus in the rabbit diet positively influenced the physicochemical properties of rabbit meat by increasing its energy value (P less than 0.05 - sage). Supplementing rabbits feed with oregano and sage extracts led to an improvement of the amino acid composition (P less than 0.01). These findings are also supported by the good health state of rabbits. The diet enriched with the plant extracts is beneficial for the health state of rabbits and the nutritional quality of rabbit meat.

Amino acid composition of the meats of wild and farm pheasants were compared. The following amino acids were determined: Asp, Thr, Ser, Glu, Pro, Gly, Ala, Val, Ile, Leu, Tyr, Phe, His, Lys, Arg. An improved amino acid profile was found in the breast muscle of pheasants kept at the farm in comparison with that of wild pheasants.

High performance liquid chromatography (HPLC) method with the pre-column derivatisation by AccQ.Tag agent and following determination of these derivates after their separation in reverse phase column followed by fluorescent detection was used for the determination of amino acids in cheeses. The contents of sixteen free amino acids in twenty five cheeses commercially available in the Czech Republic were measured. The total content of free amino acids in the studied cheeses varied in the range from 27 g/kg to 160 g/kg. Among individual amino acids, seven amino acids were more concentrated in all cheese samples and came from three distinctive taste groups: bitter tasting amino acids (leucine, lysine, and phenylalanine), bitter sweet amino acids (proline and valine), and salty-umami amino acids (glutamic acid and aspartic acid). The differences in the contents of the total and individual free amino acids were influenced by the kind of cheese and mainly by the duration and intensity of proteolysis.

The objective of this work was to verify the effect of the lean meat proportion (LMP) on the chemical composition of the meaty parts (loin and ham) of pork. A total of 116 hybrid pigs commonly used in the Czech Republic were fattened for this purpose. The pigs were divided according to the lean meat proportion criterion into 3 groups, i.e. more than 60.0%, 55.0-59.9% and 50.0-54.9%. Representative muscle samples were taken from the right halves of these pigs. They were then homogenised and submitted to chemical analysis. The values of water content, intramuscular fat (IMF), crude proteins, and ash matter were as follows: in the loin: 72.50-72.80%, 1.56-1.96%, 23.20-23.40%, and 1.37-1.40%, respectively, in the ham: 70.43-71.59%, 3.52-4.26%, 21.67-21.95%, and 1.42-1.56%, respectively. The higher the LMP, the lower the IMF content. The ash content increased with increasing LMP. The analyses of amino acid composition of musculus longissimus lumborum et thoracis (MLLT) and musculus semimembranosus (MS) showed that when the LMP increased, threonine, isoleucine, lysine, aspartic acid, serine, and proline concentrations in MLLT decreased, whereas valine, isoleucine, phenylalanine, lysine, serine, proline, and glycine conc. in MS increased. The values of IMF in MLLT, water content, IMF, ash matter, threonine, valine, phenylalanine, lysine, aspartic acid, serine, glycine, and alanine in MS differed significantly among the groups studied.

The relative proportions of free amino acids as well as the amino acid compositions of hydrolysed unprecipitated peptides and hydrolysed whole carcasses were quantified for two aphid species: the gall-dwelling social aphid Pemphigus spyrothecae and the pea aphid Acyrthosiphon pisum. The whole-tissue amino acid profiles of the two taxonomically distant species had a surprisingly high level of correspondence. In contrast, when comparing the A. pisum profiles obtained in the current study to those obtained in an earlier study, major differences were identified. It is concluded that there are good prospects for developing an artificial diet for P. spyrothecae. There may also exist considerable scope for tailoring the existing diets of A. pisum to suit specialised populations which develop poorly on the standard diet. The amino acid profile of P. spyrothecae is the first such profile that has been reported for a gall-forming aphid.

This study compares D-alanine (DAL) contents of intestinal bacteria in digesta of cows and pigs with respect to diet and sampling site. The DAL/N ratio in isolated ileal bacteria of pigs (41.72+/-3.19 mg/g, n=18) was not different from that in rumen bacteria (40.11+/-1.95 mg/g, n=18) but higher than in duodenal bacteria of cows (38.09+/-2.09 mg/g, n=18, P less than 0.001). The DAL/N ratio in ileal bacteria of pigs was independent of the diet but it tended to be affected by the animal (P=0.095). In bacterial preparations derived from cows the DAL/N ratio depended on the diet (P=0.04) and the site of sampling (P=0.004). Our findings indicate that a general value for DAL/N ratio in pig or cow intestinal contents should not be used to calculate bacterial N.

▪ Abstract  The nature of cell wall proteins is as varied as the many functions of plant cell walls. With the exception of glycine-rich proteins, all are glycosylated and contain hydroxyproline (Hyp). Again excepting glycine-rich proteins, they also contain highly repetitive sequences that can be shared between them. The majority of cell wall proteins are cross-linked into the wall and probably have structural functions, although they may also participate in morphogenesis. On the other hand, arabinogalactan proteins are readily soluble and possibly play a major role in cell-cell interactions during development. The interactions of these proteins between themselves and with other wall components is still unknown, as is how wall components are assembled. The possible functions of cell wall proteins are suggested based on repetitive sequence, localization in the plant body, and the general morphogenetic pattern in plants.

\"Soft\" and \"hard\" are the two main market classes of wheat (Triticum aestivum L.) and are distinguished by expression of the Hardness gene, Friabilin, a marker protein for grain softness (Ha), consists of two proteins, puroindoline a and b (pinA and pinB, respectively) we previously demonstrated that a glycine to serine mutation in pinB is linked inseparably to grain hardness. Here, we report that the pinB serine mutation is present in 9 of 13 additional randomly selected hard wheats and in none of 10 soft wheats. The four exceptional hard wheats not containing the serine mutation in pinB express no pinA, the remaining component of the marker protein friabilin. The absence of pinA protein was linked inseparably to grain hardness among 44 near-isogenic lines created between the soft variety Heron and the hard variety Falcon. Both pinA and pinB apparently are required for the expression of grain softness. The absence of pinA and protein and transcript and a glycine-to-serine mutation in pinB are two highly conserved mutations associated with grain hardness, and these friabilin genes are the suggested tightly linked components of the Hardness gene. A previously described grain hardness related gene termed \"GSP-1\" (grain softness protein) is not controlled by chromosome 5D and is apparently not involved in grain hardness. The association of grain hardness with mutations in both pinA or pinB indicates that these two proteins alone may function together to effect grain softness. Elucidation of the molecular basis for grain hardness opens the way to understanding and eventually manipulating this wheat endosperm property

Resistance to organophosphorus (OP) insecticides is associated with decreased carboxylesterase activity in several insect species. It has been proposed that the resistance may be the result of a mutation in a carboxylesterase that simultaneously reduces its carboxylesterase activity and confers an OP hydrolase activity (the \"mutant aliesterase hypothesis\"). In the sheep blowfly, Lucilia cuprina, the association is due to a change in a specific esterase isozyme, E3, which, in resistant flies, has a null phenotype on gels stained using standard carboxylesterase substrates. Here we show that an OP-resistant allele of the gene that encodes E3 differs at five amino acid replacement sites from a previously described OP-susceptible allele. Knowledge of the structure of a related enzyme (acetylcholinesterase) suggests that one of these substitutions (Gly 137 replaced by Asp) lies within the active site of the enzyme. The occurrence of this substitution is completely correlated with resistance across 15 isogenic strains. In vitro expression of two natural and two synthetic chimeric alleles shows that the Asp 137 substitution alone is responsible for both the loss of E3's carboxylesterase activity and the acquisition of a novel OP hydrolase activity. Modeling of Asp137 in the homologous position in acetylcholinesterase suggests that Asp 137 may act as a base to orientate a water molecule in the appropriate position for hydrolysis of the phosphorylated enzyme intermediate