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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.31, #1)

Primary kidney growth and its consequences at the onset of diabetes mellitus by J. Satriano; V. Vallon (pp. 1-9).

Diabetes mellitus is a primary contributor to progressive kidney dysfunction leading to end-stage renal disease (ESRD). In the early phase of diabetes, prior to the onset of further complications, both kidney size and glomerular filtration rate (GFR) increase. Glomerular hyperfiltration is considered a risk factor for downstream complications and progression to ESRD. Abnormalities in vascular control have been purported to account for the glomerular hyperfiltration in early diabetes. In this review we discuss a tubulo-centric concept in which tubular growth and subsequent hyper-reabsorption contribute to the onset of glomerular hyperfiltration that demarks the early stage of diabetes. Kidney growth, in this concept, is no longer relegated to a compensatory response to hyperfiltration, but rather plays a primary and active role in its genesis and progression. As such, components of kidney growth, such as the polyamines, may provide a means of early detection of diabetic kidney dysfunction and more effective therapeutic intervention.

Keywords: Keywords: Type-1 diabetes – Hyperfiltration – Tubuloglomerular feedback – Kidney – Polyamines – Hypertrophy

Nitric oxide and polyamine pathway-dependent modulation of neutrophil free amino- and α-keto acid profiles or host defense capability by J. Mühling; J. Engel; M. Halabi; M. Müller; M. Fuchs; M. Krüll; H. Harbach; T. W. Langefeld; M. Wolff; R. Matejec; I. D. Welters; T. Menges; G. Hempelmann (pp. 11-26).

We have examined the effects of N_ω-nitro-L-arginine-methylester-hydrochloride [L-NAME; inhibitor of nitric oxide synthase], S-nitroso-N-acetyl-penicillamine [SNAP; nitric oxide donor], α-difluoro-methyl-ornithine [DFMO; inhibitor of ornithine decarboxylase] arginine or ornithine as well as the combination of arginine or ornithine with L-NAME, SNAP or DFMO on intracellular free amino- and α-keto acid profiles and the immune function markers superoxide anion and hydrogen peroxide generation as well as released myeloperoxidase activity in neutrophils (PMN). Although the underlying mechanisms still remain unclear, we believe from our results that nitric oxide as well as polyamine-dependent pathways are involved in the signal transmission of free radical molecule, beneficial nutritional therapy or maleficient pharmacological stress-induced alterations in PMN nutrient composition. Relevant changes in intragranulocyte free amino- and α-keto acid homeostasis and metabolism, especially, may be one of the determinants in PMN nutrition that positively or negatively influences and modulate neutrophil host defence capability and immunocompetence.

Keywords: Keywords: Nitric oxide – Polyamines – Neutrophil – Amino acids – α-Keto acids – Immune function

Production of hypotaurine, taurine and sulfate in rats and mice injected with L-cysteinesulfinate by H. Nakamura; J. Yatsuki; T. Ubuka (pp. 27-33).

We studied in vivo production of taurine, hypotaurine and sulfate following subcutaneous administration of L-cysteinesulfinate (CSA) to rats and mice. When 5.0 mmol/kg of body weight of CSA was injected to rats, increased urinary excretions of taurine, hypotaurine and sulfate in 24 h urine were 617, 52 and 1,767 µmol/kg, respectively. From these results together with our previous data, sulfate production was calculated to be 1.6 times greater than taurine production. Increased contents (µmol/g of wet tissue) over the control of taurine and hypotaurine in mouse tissues at 60 min after the injection of 5.0 mmol/kg body weight of CSA were: liver, 3.5 and 9.9; kidney, 0.3 and 5.2; heart, 3.7 and 0.2; blood plasma, 0.4 and 0.2, respectively. Upon loading of hypotaurine or taurine, tissue contents of these amino acids in liver and kidney increased greatly. Our results indicate that liver is the most active tissue for taurine production, followed by kidney, and that external CSA, hypotaurine and taurine are easily taken up by these tissues.

Keywords: Keywords: Amino acids – Cysteine metabolism – Cysteinesulfinate – Hypotaurine – Taurine – Inorganic sulfate

Characteristics of taurine release in slices from adult and developing mouse brain stem by P. Saransaari; S. S. Oja (pp. 35-43).

Taurine has been thought to function as a regulator of neuronal activity, neuromodulator and osmoregulator. Moreover, it is essential for the development and survival of neural cells and protects them under cell-damaging conditions. Taurine is also involved in many vital functions regulated by the brain stem, including cardiovascular control and arterial blood pressure. The release of taurine has been studied both in vivo and in vitro in higher brain areas, whereas the mechanisms of release have not been systematically characterized in the brain stem. The properties of release of preloaded [³H]taurine were now characterized in slices prepared from the mouse brain stem from developing (7-day-old) and young adult (3-month-old) mice, using a superfusion system. In general, taurine release was found to be similar to that in other brain areas, consisting of both Ca²⁺-dependent and Ca²⁺-independent components. Moreover, the release was mediated by Na⁺-, Cl⁻-dependent transporters operating outwards, as both Na⁺-free and Cl⁻ -free conditions greatly enhanced it. Cl⁻ channel antagonists and a Cl⁻ transport inhibitor reduced the release at both ages, indicating that a part of the release occurs through ion channels. Protein kinases appeared not to be involved in taurine release in the brain stem, since substances affecting the activity of protein kinase C or tyrosine kinase had no significant effects. The release was modulated by cAMP second messenger systems and phospholipases at both ages. Furthermore, the metabotropic glutamate receptor agonists likewise suppressed the K⁺-stimulated release at both ages. In the immature brain stem, the ionotropic glutamate receptor agonists N-methyl-D-aspartate (NMDA) and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) potentiated taurine release in a receptor-mediated manner. This could constitute an important mechanism against excitotoxicity, protecting the brain stem under cell-damaging conditions.

Keywords: Keywords: Taurine release – Ca²⁺ dependency – Na⁺ and Cl⁻ ions – Ion channels – Second messengers – Glutamate receptors – Brain stem slices – Adult and developing mice

Near infrared spectroscopy, cluster and multivariate analysis hyphenated to thin layer chromatography for the analysis of amino acids by N. Heigl; C. W. Huck; M. Rainer; M. Najam-ul-Haq; G. K. Bonn (pp. 45-53).

A method based on near-infrared spectroscopy (NIRS) was developed for the rapid and non-destructive determination and quantification of solid and dissolved amino acids. The statistical results obtained after optimisation of measurement conditions were evaluated on the basis of statistical parameters, Q-value (quality of calibrations), R², standard error of estimation (SEE), standard error of prediction (SEP), BIAS applying cluster and different multivariate analytical procedures. Experimental optimisation comprised the selection of the highest suitable optical thin-layer (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mm), sample temperature (10–30 °C), measurement option (light fibre, 0.5 mm optical thin-layer; boiling point tube; different types of cuvettes) and sample concentration in the range between 100 and 500 ppm. Applying the optimised conditions and a 115-QS Suprasil^® cuvette (V = 400 µl), the established qualitative model enabled to distinguish between different dissolved amino acids with a Q-value of 0.9555. Solid amino acids were investigated in the transflectance mode, allowing to differentiate them with a Q-value of 0.9155. For the qualitative and quantitative analysis of amino acids in complex matrices NIRS was established as a detection system directly onto the plate after prior separation on cellulose based thin-layer chromatography (TLC) sheets employing n-butanol, acetic acid and distilled water at a ratio of 8:4:2 (v/v/v) as an optimised mobile phase. Due to the prior separation step, the established calibration curve was found to be more stable than the one calculated from the dissolved amino acids. The found lower limit of detection was 0.01 mg/ml. Finally, this optimised TLC-NIRS method was successfully applied for the qualitative and quantitative analysis of L-lysine in apple juice. NIRS is shown not only to offer a fast, non-destructive detection tool but also to provide an easy-to-use alternative to more complicated detection methods such as mass spectrometry (MS) for qualitative and quantitative TLC analysis of amino acids in crude samples.

Keywords: Keywords: Amino acid – Near infrared spectroscopy – Cluster analysis – Multivariate analysis – Thin layer chromatography

Synthesis of α-trifluoromethyl α-amino acids with aromatic, heteroaromatic and ferrocenyl subunits in the side chain by K. Burger; L. Hennig; P. Tsouker; J. Spengler; F. Albericio; B. Koksch (pp. 55-62).

5-Benzyloxy-4-trifluoromethyl-1,3-oxazoles, obtained from 5-fluoro-4-trifluoromethyloxazoles and benzyl alcohols, are capable for rearrangements. A 1,3 shift of a benzyl group is the key step of a new general route toward α-trifluoromethyl substituted aromatic and heteroaromatic amino acids, demonstrating that 5-fluoro-4-trifluoromethyl-1,3-oxazole is a synthetic Tfm-Gly equivalent. On reaction with benzpinacol partially fluorinated oxazoles are transformed into bis(trifluoromethyl) substituted 2,5-diamino adipic acid and N-benzoyl-2-benzhydryl-3,3,3-trifluoroalanine.

Keywords: Keywords: 5-Fluoro-4-trifluoromethyl-1,3-oxazoles – Nucleophilic heteroaromatic substitution – 1,3-Benzyl group migration versus Claisen rearrangement – α-Trifluoromethylamino acids – Synthetic Tfm-Gly equivalent

Gas chromatographic determination and mechanism of formation of D-amino acids occurring in fermented and roasted cocoa beans, cocoa powder, chocolate and cocoa shell by R. Pätzold; H. Brückner (pp. 63-72).

Fermented cocoa beans of various countries of origin (Ivory Coast, Ghana, Sulawesi), cocoa beans roasted under defined conditions (100–150 °C; 30–120 min), low and high fat cocoa powder, various brands of chocolate, and cocoa shells were analyzed for their contents of free L-and D-amino acids.Amino acids were isolated from defatted products using a cation exchanger and converted into volatile N(O)-pentafluoropropionyl amino acid 2-propyl esters which were analyzed by enantioselective gas chromatography mass spectrometry on a Chirasil^®-L-Val capillary column. Besides common protein L-amino acids low amounts of D-amino acids were detected in fermented cocoa beans. Quantities of D-amino acids increased on heating. On roasting cocoa beans of the Forastero type from the Ivory Coast at 150 °C for 2 h, relative quantities of D-amino acids approached 17.0% D-Ala, 11.7% D-Ile, 11.1% D-Asx (Asp + Asn), 7.9% D-Tyr, 5.8% D-Ser, 4.8% D-Leu, 4.3% D-Phe, 37.0% D-Pro, and 1.2% D-Val. In cocoa powder and chocolate relative quantities amounted to 14.5% D-Ala, 10.6% D-Tyr, 9.8% D-Phe, 8.1% L-Asx, and 7.2% D-Ile. Lower quantities of other D-amino acids were also detected. In order to corroborate our hypothesis that D-amino acids are generated from Amadori compounds (fructose amino acids) formed in the course of the Maillard reaction, fructose-L-phenylalanine and fructose-D-phenylalanine were synthesized and heated at 200 °C for 5–60 min. Already after 5 min release of 11.7% D-Phe and 11.8% L-Phe in the free form could be analyzed. Based on the data a racemization mechanism is presented founded on the intermediate and reversible formation of an amino acid carbanion in the Amadori compounds.

Keywords: Keywords: Amino acid enantiomers – Racemization – Gas chromatography mass-spectrometry – Chirasil^®-Val – Theobroma cacao L. – Maillard reaction – Amadori rearrangement products

Anti-SARS drug screening by molecular docking by D.-Q. Wei; R. Zhang; Q.-S. Du; W.-N. Gao; Y. Li; H. Gao; S.-Q. Wang; X. Zhang; A.-X. Li; S. Sirois; K.-C. Chou (pp. 73-80).

Starting from a collection of 1386 druggable compounds obtained from the 3D pharmacophore search, we performed a similarity search to narrow down the scope of docking studies. The template molecule is KZ7088 (Chou et al., 2003, Biochem Biophys Res Commun 308: 148–151). The MDL MACCS keys were used to fingerprint the molecules. The Tanimoto coefficient is taken as the metric to compare fingerprints. If the similarity threshold was 0.8, a set of 50 unique hits and 103 conformers were retrieved as a result of similarity search. The AutoDock 3.011 was used to carry out molecular docking of 50 ligands to their macromolecular protein receptors. Three compounds, i.e., C₂₈H₃₄O₄N₇Cl, C₂₁H₃₆O₅N₆, and C₂₁H₃₆O₅N₆, were found that may be promising candidates for further investigation. The main feature shared by these three potential inhibitors as well as the information of the involved side chains of SARS Cov Mpro may provide useful insights for the development of potent inhibitors against SARS enzyme.

Keywords: Keywords: SARS CoV Mpro – KZ7088 – Molecular docking – Similarity search – Inhibitor design

Diuretic potential of energy drinks by A. Riesenhuber; M. Boehm; M. Posch; C. Aufricht (pp. 81-83).

Recent literature suggests that both caffeine and taurine can induce diuresis and natriuresis in rat and man. Although they act via different cellular mechanisms, their diuretic actions might be additive. This is of considerable interest, as several commercially available energy drinks contain both substances.In this study we examined the possible diuretic effects of caffeine and taurine in a cross-over-design in which 12 healthy male volunteers received each of 4 different test drinks (750 ml of energy drink containing 240 mg caffeine and 3 g taurine, the three other test drinks either lacked caffeine, taurine or both) after restraining from fluids for 12 h.Mixed model analyses demonstrated that urinary output and natriuresis were significantly increased by caffeine (mean differences 243 ml and 27 mmol; both p < 0.001) and that there were no such effects of taurine (mean differences 59 ml and −4 mmol). Additionally, urinary osmolarity at baseline was significantly related to the urinary output (p < 0.001). Urine osmolarity values at baseline and in the 6 h urine collection did not differ significantly between treatments.Taken together, our study demonstrates that diuretic and natriuretic effects of the tested energy drink were largely mediated by caffeine. Taurine played no significant role in the fluid balance in moderately dehydrated healthy young consumers. Consequently, the diuretic potential of energy drinks will not differ significantly from other caffeine containing beverages.

Keywords: Keywords: Caffeine – Taurine – Natriuresis – Diuresis – Energy drink

Synthesis and characterization of aspartic acid complexes of antimony and bismuth triiodide by R. R. Jia; C. P. Wu; S. Wu; Y. X. Yang; Y. R. Chen; Y. Q. Jia (pp. 85-90).

New bioinorganic complexes of the aspartic acid with the antimony or bismuth triiodide were synthesized by a direct solid–solid reaction at room temperature. The formula of the complex is MI₃[OOCCH₂CH(NH₂)CO]_2.5 · 2.5H₂O (M = Sb, Bi). The complex may be a dimer with bridge structure. The crystal structure of the complexes belongs to a triclinic system. The lattice parameters are a = 0.9883 nm, b = 1.4284 nm, c = 2.0114 nm, α = 94.46°, β = 99.76° and γ = 100.1° for the complex of antimony and a = 0.9756 nm, b = 1.4560 nm, c = 1.9875 nm, α = 94.18°, β = 97.25° and γ = 101.16° for the complex of bismuth. The infrared spectra and thermal analyses can demonstrate the complex formation between the aspartic acid and the antimony or bismuth ion.

Keywords: Keywords: Aspartic acid complex of Sb or Bi – Solid solid reaction synthesis – Characterization

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.31, #1)