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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.21, #3)

Determination of diamino acids in peptidoglycans from anaerobic bacteria by S. Satyanarayana; J. S. Grossert; S. F. Lee; R. L. White (pp. 221-235).

Peptidoglycans isolated from two Fusobacterium species of anaerobic bacteria were analyzed for constituent amino acids. Hydrolysis conditions were varied to optimize the yield of diamino acids from peptidoglycan. The o-phthalaldehyde derivatives of the diamino acid stereoisomers were separated by high-performance liquid chromatography (OPA-HPLC), and variations in the relative areas of the two peaks noticed during analysis of solid samples were attributed to sampling errors. Co-derivatization/injection experiments using standards of the meso and rac forms separated from commercial mixtures demonstrated that meso-2,6-diaminopimelic acid and meso-lanthionine were peptidoglycan components in Fusobacterium varium and Fusobacterium nucleatum, respectively. The protonated molecules of 2,6-diaminopimelic acid and lanthionine were detected in peptidoglycan hydrolyzates by off-line, flow-injection electrospray mass spectrometry (ESI-MS). In ESI-MS-MS experiments under identical collision-induced dissociation (CID) conditions, peptidoglycan-derived and standard diamino acids exhibited similar fragmentations. Fragmentation pathways are proposed for each diamino acid. The results confirm that the meso forms of two different diamino acids are utilized in the peptidoglycans of Fusobacterium species.

Keywords: Keywords: Amino acids; 2; 6-Diaminopimelic acid; Fusobacterium nucleatum; Fusobacterium varium; HPLC; Lanthionine; Electrospray mass spectrometry; Peptidoglycan

Plasma total homocysteine and subarachnoid haemorrhage in a co-factor replete population by A. W. McEvoy; C. Marras; N. D. Kitchen; A. Briddon (pp. 237-241).

Mild hyperhomocysteinaemia is a postulated risk factor for occlusive vascular disease, including stroke. Subarachnoid haemorrhage (SAH) has an annual incidence of 10–20 per 100,000 and accounts for 5–10% of all strokes. Measurement of plasma total homocysteine (tHcy) in a cohort of vitamin B12 and folate replete patients did not reveal any association between tHcy and the aetiology of SAH.

Keywords: Keywords: Amino acids; Homocysteine; Subarachnoid haemorrhage; Stroke; Folate; Vitamin B12

Structure-activity relationships in coeliac-toxic gliadin peptides by H. J. Cornell; G. Wills-Johnson (pp. 243-253).

Computer modelling studies of two groups of biologically-active peptides derived from A-gliadin indicated that the most likely structures were α-helical ones, in the case of serine-containing peptides, and random peptides coil types featuring β-turns, in the case of proline-rich, tyrosine-containing peptides.The serine-containing group of peptides appear to be essentially cytotoxic in animal models of coeliac disease, whilst the tyrosine-containing group have the capacity to initiate damaging immunological reactions in patients with coeliac disease.Both types of activity in coeliac disease are only possible if there is defective digestion of the active peptides, as mucosal digestion studies indicate. In the case of the serine-containing peptides, activity of the peptides is linked to the presence of PSQQ and also probably QQQP motifs. With the tyrosine-containing peptides, sequences such as QQPY and/or QPYP are associated with immunological activity and hence toxicity.

Keywords: Keywords: Amino acid motifs; Coeliac disease; Wheat gliadin; Toxic peptides; Computer modelling

The peptides of α-aminosuberic acid II. Synthesis of deamino-dicarba-eel-calcitonin sequence 1–9 by V. Gut; V. Čeřovský; M. Žertová; E. Körblová; P. Maloň; H. Stocker; E. Wünsch (pp. 255-263).

The paper describes the synthesis of Asu⁶-octapeptide derivatives by condensing two alternative pentapeptide fragments with Asu-containing tripeptides. After partial deprotection these linear peptides compounds are subject to cyclization experiments aimed to give the N-terminal [1–9] sequence of deamino-dicarba-eel calcitonin. This is a key substance for the semi-synthesis of the respective analogues of eel calcitonin.

Keywords: Keywords:α-Aminosuberic acid; Peptide synthesis; Synthetic intermediates; Cyclic peptides; Dicarba analogues; Calcitonin analogues

Efficient synthesis of pyrenylalanine by A. Szymańska; W. Wiczk; L. Łankiewicz (pp. 265-270).

An efficient synthesis of l-3-(l′-pyrenyl)alanine (Pya), a highly fluorescent amino acid, is described. The amino acid was obtained by the classical asymmetric hydrogenation of chiral 1-acetyl-3-pyrenemethylidene-6-methyl-piperazine-2,5-dione. In the proposed improved procedure mild conditions of the synthesis were applied and the final product – N-tert-butoxycarbonyl-pyrenylalanine – was obtained in good yield. Pyrenylalanine, due to its interesting photophysical properties, can be applied as a fluorescent probe in numerous biochemical and conformational studies.

Keywords: Keywords: Amino acids; Asymmetric synthesis; Pyrenylalanine; Fluorescent compounds

Characterization of spermine uptake by Ehrlich tumour cells in culture by J. C. Paz; F. Sánchez-Jiménez; M. A. Medina (pp. 271-279).

Spermine is taken up by Ehrlich ascites tumour cells through a specific, saturable, temperature and energy-dependent transport system with a remarkably low affinity constant for spermine (around 1 μM). In the absence of a potassium ion gradient through the plasma membrane, spermine uptake remains saturable but the value of the K_m for spermine is much higher (153 μM). Difluormethylornithine treatment (3 mM for 48 h) induces significant increases in V_max values (up to 9-fold) and changes in the K_m values with scarce statistical significance. Among the biogenic amines tested, only spermidine and, partly, agmatine seem to share the same transport system with spermine. No difference is observed in the rate of spermine transport when assays are carried out in the presence of 50-fold excess of ornithine or calcium, or 100-fold excess of glutamine.

Keywords: Keywords: Amino acids; Polyamines; Spermine; Uptake; Ehrlich cells

Activated alumina as an energy source for peptide bond formation: Consequences for mineral-mediated prebiotic processes by J. Bujdák; B. M. Rode (pp. 281-291).

The catalytic properties of various forms of alumina were tested for alanine dimerization reaction. The catalytic efficiency of alumina depends on the structure, as well as on acid/base properties of the catalyst. The highest yields of Ala₂ were achieved on activated alumina with surface of neutral pH (about 3% conversion after 2 weeks). Thermal analysis of Ala + alumina reaction systems shows that the thermal behavior of amino acid changes substantially in contact with the activated surface of the alumina catalyst. The reaction of Ala is detected as being strongly endothermic by differential thermal analysis of pure amino acid (above 250°C). The alanine endothermic reaction is shifted substantially to lower values (below 200°C) and hardly detectable if activated alumina is present. The reaction mechanism of amino acid activation on alumina surface and its significance for mineral-catalyzed prebiotic peptide bond formation are discussed.

Keywords: Keywords: Amino acids; Alumina; Alanine; Catalysis; Clay; Peptide bond formation; Prebiotic

Neurofilament proteins NF-L, NF-M and NF-H in brain of patients with Down syndrome and Alzheimer's disease by M. Bajo; B. C. Yoo; N. Cairns; M. Gratzer; G. Lubec (pp. 293-301).

Neurofilaments (NFs) are integral constituents of the neuron playing a major role in brain development, maintenance, regeneration and the pattern of expression for NFs suggests their contribution to plasticity of the neuronal cytoskeleton and creating and maintaining neuronal architecture. Using immune-histochemical techniques the altered expression of NFs in Down syndrome (DS) and Alzheimer's disease (AD) has been already published but as no corresponding systematic immune-chemical study has been reported yet, we decided to determine proteins levels of three NFs in several brain regions of DS and AD brain.We evaluated immunoreactive NF-H, NF-M and NF-L levels using Western blotting in brain regions temporal, occipital cortex and thalamus of patients with DS (n = 9), AD (n = 9) and controls (n = 12). We found significantly increased NF-H in temporal cortex (controls: means 0.74 ± 0.39 SD; DS: means 3.01 ± 2.18 SD) of DS patients and a significant decrease of NF-L in occipital cortex of DS and AD patients (controls: means 1.19 ± 0.86 SD; DS: means 0.35 ± 0.20; AD: 0.20 ± 0.11 SD).We propose that the increase of NF-H in temporal cortex of DS brain is due to neuritic sprouting as observed in immune-histochemical studies. The increase may not be caused by the known accumulation of NFs in plaques, tangles or Lewy bodies due to our solubilization protocol. The decrease of NF-L in occipital cortex of DS and AD patients may well be reflecting neuronal loss. Altogether, however, we suggest that NFs are not reliable markers for neuronal death, a hallmark of both neurodegenerative diseases, in DS or AD. The increase of NF-H in DS or the decrease of NF-L in DS and AD leaves the other NFs unchanged, which points to dysregulation in DS and AD and raises the question of impaired structural assembly of neurofilaments.

Keywords: Keywords: Amino acids; Down syndrome; Alzheimer's disease; Neurofilaments; NF-L; NF-M; NF-H

Conscientious metabolic monitoring on a patient with hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome undergoing anaesthesia by J. Mühling; M. G. Dehne; M. Fuchs; A. Sablotzki; S. Weiss; J. Spatz; G. Hempelmann (pp. 303-318).

Currently we know not more than 50 patients who show an interesting combination of increased plasma ornithine concentrations, postprandial hyperammonemia, and homocitrullinuria (HHH-syndrome). Since exact knowledge of this severe, although rare syndrome is important for any perioperative or intensive medical treatment concerning therapy and progression of the disease, we report a comprehensive study on a 32-year old woman with this rare multifaceted disorder who had to undergo general anaesthesia. For the first time amino acid status in plasma, urine, cerebrospinal fluid and especially polymorphonuclear leucocytes, which in the investigation showed to be valuable tool for evaluating amino acid metabolism in nucleated cells in HHH-syndrome, and further important pathophysiologic indicators of cellular and metabolic function have been conscientiously investigated and compared. The pathophysiological repercussions of our results as well as the recommendations for conscientious therapeutical management are discussed.

Keywords: Keywords: Amino acids; HHH-syndrome; PMN; Liquor; Urine; Amino acids; Coagulation analyses

l-Canavanine: a higher plant insecticidal allelochemical by G. A. Rosenthal (pp. 319-330).

l-Canavanine, l-2-amino-4-(guanidinooxy)butyric acid, is a potentially toxic nonprotein amino acid of certain leguminous plants. Many species are prolific canavanine producers; they divert enormous nitrogen resource to the storage of this single natural product. Canavanine, a highly effective protective allelochemical, provides a formidable chemical barrier to predation and disease.The accumulated experimental evidence leaves little doubt that the key element in the ability of canavanine to function as an effective protective allelochemical is its subtle structural mimicry of arginine which makes it an effective substrate for amino acid activation and aminoacylation, and its marked diminution in basicity relative to arginine which mediates the production of structural aberrant, dysfunctional canavanyl proteins.The biological burdens of canavanyl protein formation by canavanine-treated Manduca sexta larvae were carried throughout their remaining life cycle. Protein-based sequestration of canavanine prevented turnover and clearance of the free amino acid, and undoubtedly contributed significantly to the antimetabolic character of this protective allelochemical.

Keywords: Keywords: Amino acids; l-Canavanine; Allelochemical; Natural products

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.21, #3)