No abstract

Twelve neutral free amino acids, i.e. serine, threonine, glutamine, asparagine, alanine, proline, methionine, tyrosine, valine, leucine, isoleucine and phenylalanine, were surveyed for the presence of D-enantiomers in plasma samples from patients with renal diseases and from normal subjects. D-serine, D-alanine and D-proline were found in the patient's plasma. The highest concentrations (D/L ratio) of D-serine, D-alanine and D-proline were 0.2362, 0.2087 and 0.0986, respectively. The sum of the contents of the three D-amino acid was shown to be present in the plasma proteins.

Helicobacter pylori whole cells showed high rates of oxygen uptake with L-serine and L-proline as respiratory substrates, and somewhat lower rates with D-alanine and D-proline. These respiratory activities were inhibited by rotenone and antimycin A at low concentrations. Since pyruvate was produced from L-serine and D-and L-alanine in whole cells, the respiratory activities with these amino acids as substrates occurred via pyruvate. Whole cells showed 2,6-dichlorophenolindophenol (DCIP)-reducing activities with D-and L-proline and D-alanine as substrates, suggesting that hydrogen removed from these amino acids also participated in oxygen uptake by the whole cells. High amounts of L-proline, D-and L-alanine, and L-serine were present in H. pylori cells, and these amino acids also predominated in samples of human gastric juice. H. pylori seems to utilize D-and L-proline, D-alanine and L-serine as important energy sources in its habitat of the mucous layer of the stomach. INTRODUCTIONHelicobacter pylori is a Gram-negative bacterium associated with gastric inflammation and peptic ulcer disease and is a risk factor for gastric cancer (Blaser, 1990;Parsonnet et al., 1991Parsonnet et al., , 1994Rabeneck & Ransohoff, 1991). The natural habitat of H. pylori is the mucous layer of the human gastric epithelium, where populations are considered to persist for the lifetime of the host. H. pylori is a microaerophilic bacterium exhibiting a strict respiratory form of metabolism and oxidizing organic acids as an energy source. The carbohydrate utilized by H. pylori as the energy source has been reported to be only glucose . More recently the whole-genome analysis of H. pylori has supported these findings (Tomb et al., 1997). However, the incorporation of glucose from the culture medium was not influenced by inhibitors known to affect other bacterial glucose-related enzymes, such as glucose permease, and the K m value of its glucose transport was reported to be rather high, 4?8 mM (Burns & Mendz, 2001). In addition, glucose added to the culture medium composed of a mixture of amino acids was not utilized until the amino acids were significantly depleted Mendz & Hazell, 1995). These results suggested that glucose is not a preferred energy substrate of H. pylori. Candidates for the substrates of energy metabolism in this organism are thought to be organic acids such as pyruvate, D-lactate and succinate. Chang et al. (1995) reported that lower concentrations (25 mM) of pyruvate, D-lactate and succinate were rapidly oxidized, and the respiration rates were relatively high, suggesting that H. pylori cells may have adapted to utilizing these substrates in vivo. However, the oxygen uptake during lactate and pyruvate oxidation was insufficient for their complete oxidation to CO 2 and H 2 O via the citric acid cycle (Chang et al., 1995;Kelly et al., 2001). Thus, instead of organic acids, amino acids are considered to be other potential respiratory substrates and energy sources in H. pylori cells.Little study has been done on amino acids...

Araneoid spiders use specialized abdominal glands to produce up to seven different protein-based silks/glues that have various mechanical properties. To date, the fibroin sequences encoding egg case fibers have not been fully determined. To gain further understanding of a recently reported spider silk protein gene family, several novel strategies were utilized in this study to isolate two full-length cDNAs of egg case silk proteins, cylindrical silk protein 1 (CySp1, 9.1 kb) and cylindrical silk protein 2 (CySp2, 9.8 kb), from the wasp spider, Argiope bruennichi. Northern blotting analysis demonstrated that CySp1 and CySp2 are selectively expressed in the cylindrical glands. The amino acid composition of raw egg case silk was closely consistent with the deduced amino acid composition based on the sequences of CySp1 and CySp2, which supports the assertion that CySp1 and CySp2 represent two major components of egg case silk. CySp1 and CySp2 are primarily composed of remarkable homogeneous assemble repeats that are 180 residues in length and consist of several complex subrepeats, and they contain highly homologous C-termini and markedly different N-termini. Our results suggest a possible link between CySp1 and CySp2. In addition, comparisons of stress/strain curves for dragline and egg case silk from Argiope bruennichi showed obvious differences in ultimate strength and extensibility, and similarities in toughness.

The concentrations of free D- and L-amino acids were determined in the gastric juice from four groups: patients suffering from early gastric carcinoma with or without Helicobacter pylori infection, and patients without carcinoma but with peptic ulcers, duodenal ulcers or chronic gastritis with or without H. pylori infection. H. pylori is a bacterium associated with gastric inflammation and peptic ulcers and is a risk factor for stomach cancer. The highest D-amino acid ratios (free D-amino acid concentration to the total corresponding free D- and L-amino acid concentration) were 29%, 26%, 18%, 4% and 1% for proline, alanine, serine, aspartate and glutamate, respectively. The gastric juice levels of L-alanine, L-serine, L-proline, L-glutamate and D-alanine in the samples obtained from subjects bearing early gastric carcinoma and H. pylori were significantly higher than in the samples from the other three groups. Except for D-alanine, there was no correlation between the D-amino acid concentrations and presence of carcinoma or H. pylori.