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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.12, #2)

Amino acid studies in transient acute polymorphic psychosis by Dr. D. Fekkes; L. Pepplinkhuizen (pp. 107-117).

Data are reviewed on the amino acid metabolism in patients suffering from transient acute polymorphic psychoses according to ICD-10. The psychotic episodes of many of these patients are characterized by distorted sensory perceptions and intense emotional states; plasma amino acid analysis revealed a disturbed serine-glycine metabolism.In remitted patients oral loading with serine induced the characteristic dysperceptions and psychedelic symptoms. Plasma concentrations of serine and methionine were decreased, and the concentration of taurine was increased. Fibroblast experiments suggest that the activities of the serine metabolizing enzymes serine hydroxymethyltransferase and cystathionineβ-synthase are increased in these patients.The determination of plasma amino acid concentrations proved to be useful in discriminating these patients. The prevalence of this transient psychosis in a psychiatric in-patient population ranged between 1.4 and 3.6%.

Keywords: Amino acids; Serine; TSM-ratio; Acute polymorphic psychosis

Portal-drained viscera and hepatic fluxes of branched-chain amino acids do not account for differences in circulating branched-chain amino acids in rats fed arginine-deficient diets by W. J. Hartman Ph.D.; R. L. Prior Ph.D. (pp. 119-137).

Concentrations and fluxes of amino acids across the portal-drained viscera (PDV) and liver were assessed in rats fed a meal of one of three arginine-deficient diets containing either alanine or the arginine precursors, ornithine or citrulline. A previous report included findings of seven arginine-related amino acids and indicated that only the citrulline-containing diet protected blood arginine concentrations. In the present report we extend these findings and note that the concentrations and fluxes of the non-arginine-related amino acids showed remarkable consistency across diet groups. However, total branched-chain amino acid (BCAA) concentrations of arterial blood were higher in rats fed the - Arg/+ Ala and the - Arg/+ Orn diets than in rats fed the control (+ Arg) diet. The elevated BCAA correlated with higher circulating concentrations of other essential amino acids but were inversely correlated with arginine concentrations. PDV and hepatic fluxes of BCAA were not different across diet groups, indicating that amino acid absorption and hepatic utilization of BCAA were generally comparable across diet groups. Hepatic concentrations of 14 of 22 measured amino acids, including total BCAA, were correlated with their arterial concentrations. The circulating concentrations and net PDV and hepatic fluxes of rats fed the control diet were comparable to our previous observations in fed rats and illustrate the role of the liver in utilization of diet-derived essential amino acids.

Keywords: Essential amino acids; Fed state; Interorgan flux; Rats; Arginine deficiency

Identification of a specific protein in the mitochondrial fraction of the rat heart whose phosphorylation is inhibited by taurine by Dr. J. B. Lombardini (pp. 139-144).

It was previously reported that the mitochondrial fraction of the rat heart contained a specific protein with a molecular weight of approximately ∼44kDa whose phosphorylation was inhibited by taurine (Lombardini,1994a). Isolation of the ∼44kDa phosphoprotein on a 1-dimensional polyacrylamide gel using traditional glycine buffers followed by re-electrophoresing the cut out proportion of the gel which corresponds to the ∼44kDa protein on a tricine-buffered gel resulted in sufficient pure protein for sequence analysis. The results indicate that the ∼44kDa phosphoprotein is pyruvate dehydrogenase.

Keywords: Amino acids; Taurine; Pyruvate dehydrogenase; Mitochondria; Rat heart; Phosphorylation

Expression of ornithine carbamoyltransferase gene in rat hepatoma-derived cell lines, H4-II-E and R-Y121B by M. Shinohara; Dr. R. Konno; S. Nagashima; Y. Imai; A. Niwa (pp. 145-155).

The rat R-Y121B cell line is a unique cell line which has ornithine carbamoyltransferase (OCT, EC 2.1.3.3) and can be continuously cultured in a serum-free medium which lacks arginine but is supplemented with ornithine. The OCT gene expression was examined in R-Y121B cells and their parental H4-II-E cells. OCT activity in R-Y121B cells was about one-tenth of that of the adult rat liver while it was not detected at all in H4-II-E cells. Southern hybridization using an OCT cDNA probe containing the entire coding region showed that the OCT gene structure was apparently not different in R-Y121B cells, H4-II-E cells, or rat liver cells. Northern hybridization using the OCT cDNA probe detected a hybridizing signal in R-Y121B cells but not in H4-II-E cells. Reverse transcription-polymerase chain reaction (RT-PCR) showed that an expected size of the OCT cDNA fragment was amplified in R-Y121B cells but not in H4-II-E cells. The amplified fragment was confirmed to be a real rat OCT cDNA by the digestion of this fragment with two restriction enzymes and by the nucleotide sequencing of the fragment. These results indicated that OCT mRNA was present in R-Y121B cells but not in H4-II-E cells. Amino acid analysis showed that arginine was not present in the culture medium but was present in the hydrolysate of R-Y121B cells. The present experiments indicate that transcription, translation, and processing of OCT proceeds normally and the resultant OCT functions in R-Y121B cells, whereas the transcription does not occur in parental H4-II-E cells even though these cells have the normal gene.

Keywords: Amino acids; Ornithine carbamoyltransferase; Rat hepatoma cell line; Southern hybridization; Northern hybridization; PCR; Enzyme activity

Plasma carnitine status - a prognostic factor in children with dilated cardiomyopathy by Dr. M. Marx; M. Skyllouriotis; E. Legenstein; E. Proll; M. Wimmer (pp. 157-166).

Objective - Dilated cardiomyopathy is a rare disorder in childhood that results in a high mortality. The aim of our study was to evaluate the prognostic relevance of the individual plasma carnitine status in children with dilated cardiomyopathy. Methods - In 26 patients plasma carnitine concentrations were determined before and after 6 and 12 months of L-carnitine treatment. According to the plasma short chain acyl-carnitine/free carnitine ratio (AC/FC) at the first presentation children were divided into two groups. Results - In group 1 (AC/FC < 0.4) the median time from diagnosis until death was 35.8 months, the cumulative survival rate was 84% after 2 years. In group 2 (AC/FC > 0.4) median time from diagnosis until death was 8 months, the cumulative survival rate was 50% at 2 years (p < 0.05).Dividing both groups into survivors and nonsurvivors in group 2 a significantly higher AC/FC ratio in the nonsurvivors could be found (survivors 0.78 v 1.3 in nonsurvivors). A significant improvement of left ventricular function 6 and 12 months after presentation and after starting L-carnitine treatment could only be documented in the surviving patients of group 2. Conclusion - The individual plasma carnitine status in children with dilated cardiomyopathy may serve as a risk factor for survival.

Keywords: Amino acids; Dilated cardiomyopathy; Infants and children; Plasma carnitine

Distribution of mapping points of 20 amino acids in the tetrahedral space by Ren Zhang M.D. (pp. 167-177).

Based on the genetic codes and a simple theorem for the geometrical property of the regular tetrahedron, each amino acid is mapped onto a unique point in a 3-dimensional tetrahedral space. The distribution of the 20 mapping points for 20 amino acids is studied in detail. It is found that the mapping points for the hydrophobic and hydrophilic amino acids are distributed at distinct regions in the 3-dimensional space. A plane separating the two kinds of points satisfactorily based on the Fisher's algorithm has been calculated. It is shown that the codons coding for the hydrophobic amino acids are constituted dominantly by the bases of keto group, i.e., G and T. While the codons coding for the hydrophilic amino acids are constituted dominantly by the bases of amino group, i.e., A and C. The biological implication of the mapping points and the separating plane has been discussed in some details.

Keywords: Amino acids; Mapping point; Hydrophobicity; Hydrophilicity; Separating plane; Fisher's algorithm

Phenytoin protected mouse cortical cell cultures against neurotoxicity induced by kainate but not by NMDA by H. Furue; N. Fudamato; Y. Ohtubo; K. Yoshii Ph.D. (pp. 179-184).

Phenytoin (PHT) protected cultured mouse cortex neurons against kainate-induced excitotoxicity, but failed to protect against the N-methyl-D-aspartate (NMDA)-induced excitotoxicity. The voltage-clamp experiments showed that PHT significantly blocked kainate-induced currents but did not block NMDA-induced currents in the cultured neurons. These results indicate that PHT protects the cultures by blocking non-NMDA receptors and suggest that PHT has clinical efficacy against neuronal cell death through the excessive stimulation of non-NMDA receptors.

Keywords: Amino acids; Excitotoxicity; Voltage clamp; Diphenylhydantoin; DPH; PHT; LDH

Synthesis and characterisation of D-amino acid-based oligopeptides for use as probes of the influence of molecular structure on the paracellular route of gastrointestinal drug uptake by R. Wilcock; P. Speers; G. Warhurst; M. Rowland; Prof. K. T. Douglas (pp. 185-189).

A series of peptides based on D-amino-acids, and with an N-terminal D-phenylalanine residue, was synthesised by solution methods using t-butoxycarbonyl amino protection. These peptides were designed to resist metabolism in the gastrointestinal tract and to serve as probes of the effects of molecular shape and charge on the paracellular route of drug uptake in the gut. The peptides were characterised by NMR spectroscopy, FAB mass spectrometry, optical rotation and purified by HPLC.

Keywords: D-amino acids; Paracellular; Drug delivery; Oral absorption

Canavanine derivatives useful in peptide synthesis by Dr. T. Pajpanova; S. Stoev; E. Golovinsky; G. -J. Krauß; J. Miersch (pp. 191-204).

The objective of this work is to investigate the possibilities for introducing the currently used Nα-, N_G- and C-protective groups into the canavanine molecule and the preparation of canavanines selectively blocked at the guanidino function. These novel compounds will find application in the synthesis of canavanine derivatives expected to be amino acid antimetabolites and of canavanine modified biologically active peptides.

Keywords: Amino acids; Canavanine; Canavanine derivatives-antimetabolites; Alkaline protease; Penicillin amidase

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.12, #2)