Check out our New Publishers' Select for Free Articles

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.13, #3-4)

The proline biosynthesis in living organisms by B. Aral; Pr. P. Kamoun (pp. 189-217).

In this article we review recent work on the physiology of proline and Δ¹-pyrroline-5-carboxylate (P5C) in living organisms and consider recent progress in our understanding of the role of P5C synthetase in collagen metabolism and the regulation of urea cycle in vertebrates. Much of this recent progress has been made possible by advances in our knowledge of the enzymes and genes involved in proline biosynthesis in man. The availability of well characterized P5C synthetase deficiency in man has been an impetus for the cloning of the cDNA encoding for this enzyme from man and facilitated the establishment of the phenotype-genotype relationships in P5C synthetase deficiency in higher vertebrates.

Keywords: Proline; Δ¹-pyrroline-5-carboxylate synthetase; cDNA; Collagen; Urea cycle

Feeding and arginine deficient diets differentially alter free amino acid concentrations of hindlimb muscle in young rats by W. J. Hartman Ph.D.; R. L. Prior Ph.D. (pp. 219-236).

The objective of these experiments was to examine short- and long-term (7 d) effects of arginine-deficient diets on free amino acid concentrations in hindlimb muscle of rats. In rats fed the control diet containing arginine (+Arg), muscle alanine and methionine concentrations were higher 1 and 2h after feeding compared to food-deprived rats, whereas branched-chain amino acids, arginine and asparagine concentrations were lower postprandially. In Experiment 1, rats were fed an arginine-deficient (−Arg) diet with glutamate (+Glu) substituted for arginine; alanine (+Ala), ornithine (+Orn) or citrulline (+Cit) were substituted for arginine in Experiment 2. In Experiment 1, arginine concentrations decreased in blood but not in muscle. This contrasts with rats fed −Arg/+Ala or −Arg/+Orn diets which had muscle arginine concentrations less than half the concentrations in controls or in rats fed the −Arg/+Cit diet. Muscle essential amino acids in Experiment 2 did not differ by diet, but muscle branched-chain amino acids were elevated relative to controls in the rats fed −Arg/+Ala or −Arg/+Orn diets; however, rats fed the −Arg/+Cit diet had levels similar to the controls. Also, muscle branched-chain amino acids were correlated with glutamine concentrations in both blood and muscle. The measurements in the post-meal period suggest that muscle amino acid concentrations may more closely reflect dietary amino acid patterns than do blood amino concentrations.

Keywords: Amino acids; Muscle; Fed state; Arginine deficiency; Rats

Modeling properties of biochemical compounds with connectivity terms by Prof. L. Pogliani (pp. 237-255).

The descriptive and utility power of linear combinations of connectivity terms (LCCT) derived by a trial-and-error procedure from a medium-sized set of 8 connectivity indices: {χ} = {D, D^v,⁰ χ,⁰ χ ^v,¹ χ,¹ χ ^v,χ _t,χ _t ^v} or from a subset of it has been tested on properties of heterogeneous classes of biochemical compounds centered on the homogeneous class of natural L-amino acids. To choose the appropriate combination of indices the forward selection and the complete combinatorial technique have been used, whenever more than a single term was necessary for the description. The forward selection technique searches only a subspace of the complete combinatorial space, but nevertheless has many advantages among which to be a good tool for an elementary and direct test for newly defined indices. The modeling has been followed centering the attention not only on the predictive power of the proposed linear equations but also on their utility. The modeling of the solubility of the entire heterogeneous class of n = 43 amino acids, purities and pyrimidines could satisfactorily be achieved with a set of supraconnectivity terms based on theχ _t ^v index mainly. The unfrozen water content of a mixed class of inorganic salts and natural amino acids has satisfactorily been modeled with two connectivity terms and the modeling shows a remarkable utility. The utility of the given LCCT can nevertheless be enhanced, especially when the modeling requires 2 or more terms, with the introduction of the corresponding orthogonal indices, as can be seen for S(AA + PP) and UWC.Further, theδ cardinal number is used as starting point for the definition of a supravalence index Δ to be used for a topological codification of the genetic code and the amino acids in proteins. In fact, the notion of supravalence can be extended to the triplet code words to generate the different families and subfamilies of the genetic code and to visualize the connections of amino acids in proteins. Three properties of the DNA-RNA bases (U, T, A, G and C), the singlet excitation energies ΔE₁ and δE₂, and the molar absorption coefficient ε₂₆₀ have been simulated with a single connectivity term chosen from the same medium-sized set of 8 molecular connectivity indices.

Keywords: Amino acids; Modeling; Connectivity terms; Properties; Purines and pyrimidines

Increasing dispensable amino acids in diets of kittens fed essential amino acids at or below their requirement increases the requirement for arginine by T. P. Taylor; J. G. Morris; P. H. Kass; Q. R. Rogers (pp. 257-272).

Kittens fed diets containing 0.75 × the NRC (1986) essential amino acid requirement (EAArq) and 210 to 560g crude protein(CP)/kg diet exhibited, with increasing CP: 1) decreasing weight gain, 2) decreasing plasma arginine concentrations, 3) increasing urinary orotic acid excretion, 4) increasing plasma glutamic acid concentrations, and 5) plasma isoleucine concentrations at levels that suggest a marginal isoleucine deficiency. Kittens fed a control diet (CD) containing 1.5 × EAArq and 350 g CP/kg diet had maximal weight gains and no orotic aciduria. It was concluded that the decreased weight gain and adverse metabolic effects were caused by arginine deficiency and possibly glutamic acid toxicity induced by high dietary dispensable amino acids. Kittens fed the diets containing 1.0 × EAArq and 350 and 560 g CP/kg diet had depressed plasma arginine and elevated glutamic acid concentrations and orotic aciduria. These results indicate that 10 g arg/kg diet is not adequate at CP concentrations above 280 g/kg and the calculated requirement of arginine is (0.02 g arginine/g CP) × (Y g CP/kg diet) + (4.0 g arginine/kg diet) where Y is the dietary CP level.

Keywords: Essential amino acids; Dispensable amino acids; Crude protein; Orotic acid; Feline

Dimers formation by cytochrome c-catalyzed oxidation of tyrosine and enkephalins by C. Foppoli; C. De Marco; C. Blarzino; R. Coccia; L. Mosca; Prof. M. A. Rosen (pp. 273-280).

Cytochrome c in the presence of H₂O₂ is able to oxidize tyrosine and enkephalins into the corresponding dimers linked by a o,o′-biphenyl link, as evidenced by the spectral and HPLC analysis. Also amino acid analysis of the hydrolysates from cytochrome c-treated enkephalins provides evidence for the presence of dityrosine. Kinetics of the oxidation was followed both spectrophotometrically and fluorometrically. The reaction rate depends on cytochrome c and hydrogen peroxide concentrations. For the first time it is demonstrated that the o,o′-biphenyl link of dityrosine can be formed by the action of an enzymatic system alternative to peroxidase. Some general considerations on the possible consequences of these reactions inside the mitochondrion are outlined.

Keywords: Amino acids; Dityrosine; Enkephalin; Cytochrome c; Hydrogen peroxide

Regulation of taurine accumulation in the ciliate protozoanTetrahymena pyriformis by B. Kramhøft; J. Mollerup; Dr. I. H. Lambert (pp. 281-297).

Tetrahymena pyriformis suspended in an inorganic medium accumulates³H-labelled taurine against a concentration gradient resulting in a cellular to extracellular taurine gradient of about 3 within 2 hours. This is observed in spite of the fact that taurine influx inTetrahymena via the saturable, Na¹-dependent system and the leak pathway becomes gradually reduced with time after transfer to an inorganic, taurine free medium. Taurine is not accumulated byTetrahymena at pH below 7.0 or when protein synthesis is prevented by addition of cycloheximide. Addition of actinomycin D has no effect on the taurine accumulation. It is suggested that the transporter responsible for taurine accumulation inTetrahymena has a pH threshold of 7.0 and that translation but not transcription is conditional for the emergence of the transporter following transfer to inorganic medium. Taurine accumulation is reduced when the phosphatase inhibitor calyculin A is added at the initiation of starvation but unaffected when the inhibitor is added once the cells are in the inorganic medium. Addition of forskolin significantly enhances taurine accumulation. It is proposed that phosphorylation as well as dephosphorylation are involved in the regulation of taurine accumulation inTetrahymena pyriformis.

Keywords: Amino acids; Cycloheximide; Actinomycin D; Adenosine nucleotides; Calyculin A; Forskolin; pH-dependence; Taurine transport

Ornithine decarboxylase inThermus thermophilus: An RNA-associated enzyme by A. A. Pantazaki; M. Liakopoulou-Kyriakides; D. A. Kyriakidis (pp. 299-309).

Ornithine decarboxylase (ODC) ofThermus thermophilus is associated with the nucleoid protein fraction. Analysis of this fraction by agarose gel electrophoresis and immunostaining revealed that ODC was bound to two groups of RNA-protein complexes. These two complexes of 1.5 and 0.6 kb in size disappeared from the gel by RNase A treatment or migrated to small molecular weight complexes by proteinase K treatment. Phenol extraction of either the nucleoid fraction or the eluted RNA-protein complexes from the agarose gel, shows that both contain the 0.56kb RNA. Both RNA-protein complexes contain the ODC protein (55 kDa) but their protein composition differs in at least six proteins. Extraction of the nucleoid fraction with H₂SO₄, indicates that ODC was present in the acid-soluble fraction, showing that it is a non-histone protein tightly bound to 0.56kb RNA. The purified ODC by various columns (∼140-fold), is close to homogeneity and still carries the 0.56kb RNA further explaining all the difficulties in the purification of this enzyme.

Keywords: Amino acids; Ornithine decarboxylase; Thermus thermophilus ; RNA complex

Influence of an extracellular volume expansion (ECVE) on renal amino acid- and sodium handling in patients with autosomal dominant polycystic kidney disease (ADPKD) by R. Hartung; A. Humbsch; G. Stein; Prof. Dr. Ch. Fleck (pp. 311-322).

Although ADPKD is one of the first kidney diseases to be understood from the gene to the pathogenesis of clinical abnormalities, there were no data concerning the renal handling of amino acids and possible disorders of amino acid (AA) pattern in these patients. Therefore, in 9 patients suffering from ADPKD and in 8 healthy normal persons (NP) renal amino acid excretion was measured before and after extracellular volume expansion (ECVE) (21 of physiological electrolyte solution). Renal function was stable in both groups (serum creatinine: ADPKD: 85.1 ± 18.4 vs. NP 84.4 ± 13.5 μmol/l; GFR: 93.8 ± 16.4 vs. 104.4 ± 9.4 ml/min/1.73 m²). Mean blood pressure was higher in ADPKD patients than in NP (99.4 ± 2.6 vs. 85.5 ± 2.4 mmHg), but did not change after ECVE. After ECVE in both groups, urine volume increased distinctly, whereas GFR was only slightly enhanced. The plasma concentrations of leucine, glycine, valine, threonine, glutamine, and alanine were significantly higher in controls than in ADPKD patients. The amino acid reabsorption capacity was reduced in ADPKD patients in 12 of 21 amino acids before ECVE. After ECVE, the fractional excretion of amino acids (FE_AA) increased only in NP. In parallel with changes in amino acid handling, the FE_Na (%) after ECVE increased both in ADPKD patients and in NP (before ECVE - ADPKD: 1.22 ± 0.23 vs. NP: 1.53 ± 0.23; after ECVE: 3.17 ± 0.25 (ADPKD) vs. 2.74 ± 0.22/NP; (ADPKD p ≤ 0.01, NP p ≤ 0.02) whereas FE_Li (%) increased significantly only in ADPKD (p ≤ 0.045) range (before ECVE - ADPKD: 25.8 ± 8.9 vs. NP: 20.5 ± 4.0; after ECVE: 41.4 ±15.4 vs. 25.2 ± 3.9). Furthermore, concentrations of cGMP (pmol/ml) in plasma increased after ECVE (before ECVE - ADPKD: 5.31 ± 0.56 vs. NP: 6.65 ±0.79; after ECVE: 11.31 ± 1.66 vs. 11.30 ± 1.91; p ≤ 0.05). Na⁺-dependent and, perhaps, NO-mediated processes in the reabsorption of AA in the proximal tubule seem to be different in ADPKD and may be related to different distributions of receptors and ATP-dependent transport systems with pathogenetic impact on abnormal transtubular fluid transport in ADPKD.

Keywords: Amino acids; ADPKD; Renal failure; Renal amino acid-/sodium handling; Hypertension; Nitric oxide; Cyclic GMP; Na⁺/K⁺-ATPase

Glutamate-agonist-evoked taurine release from the adult and developing mouse hippocampus in cell-damaging conditions by P. Saransaari; S. S. Ojal (pp. 323-335).

Taurine is a neuromodulator and osmoregulator in the central nervous system, also protecting neural cells against excitotoxicity. The effects of the ionotropic glutamate receptor agonists N-methyl-D-aspartate (NMDA), kainate and 2-amino-3-hydroxy-5-methyl-4-imidazolepropionate (AMPA) on [³H]taurine release from hippocampal slices from 3-month-old and 7-day-old mice were studied in cell-damaging conditions. Neural cell injury was induced by superfusing the slices in hypoxic, hypoglycemic and ischemic conditions and by exposing them to metabolic poisons, free radicals and oxidative stress. The release of taurine was greatly enhanced in these conditions at both ages, except in oxidative stress. In normal conditions the three glutamate agonists potentiated taurine release in the immature hippocampus in a receptor-mediated manner, but kainate receptors did not participate in the regulation in the adults. The ability of the agonists to evoke taurine release varied in the cell-damaging conditions, but the glutamate-receptor-activated release was generally operating in the immature hippocampus. This glutamate-receptor-evoked massive release of taurine could have significant neuroprotective effects, particularly in the developing hippocampus, countering the harmful actions of the simultaneously liberated excitatory amino acids.

Keywords: Amino acids; Taurine release; Glutamate agonists; Cell damage; Tissue slices; Hippocampus

Protection against cell damage due to hypoxia and reoxygenation: The role of taurine and the involved mechanisms by Prof. Dr. D. V. Michalk; P. Wingenfeld; Ch. Licht (pp. 337-346).

The effect of taurine on cell viability and metabolism of human colon and porcine renal cells was investigated during and after hypoxia. Taurine administered during hypoxia markedly reduced cellular deterioration due to hypoxia and reoxygenation and led to a significantly greater recovery of cellular function following the hypoxic insult. The responsible mechanisms for the beneficial effects were an improvement in osmotic status and calcium homeostasis and an induction in cellular growth despite oxygen deficiency and reoxygenation. Free oxygen radical generation and lipid membrane peroxidation were not reduced by taurine. Taurine acted as a potent endogenous agent with multifactorial effects against cellular damage due to hypoxia and reoxygenation.

Keywords: Amino acids; Taurine; Hypoxia; Reoxygenation; Free radicals; cell growth; calcium metabolism; monolayer cell culture; LLC PK 1; HT 29

Growth and polyamine metabolism inPyrenophora avenae exposed to cyclohexylamine and norspermidine by C. A. Mackintosh; D. R. Walters (pp. 347-354).

The effectiveness of inhibitors of polyamine biosynthesis in controlling plant pathogenic fungi is well established. The spermidine synthase inhibitor cyclohexylamine (CHA) and the spermidine analogue norspermidine were evaluated againstin vitro growth of the oat stripe pathogenPyrenophora avenae. Mycelial growth was reduced by 55% upon exposure to 2.0mM CHA while the same concentration of norspermidine reduced growth by 63%. Neither inhibitor had any effect on ODC or AdoMetDC activities, nor the flux of label from ornithine through to the polyamines. Levels of free polyamines in fungal tissue exposed to 0.01 mM norspermidine were unaltered, although 1.0mM CHA did produce a 75% increase in fungal putrescine content. These data suggest that CHA and norspermidine do not reduce fungal growth as a result of a perturbation in polyamine biosynthesis.

Keywords: Amino acids; Polyamines; Spermidine; Cyclohexylamine; Norspermidine; Spermidine synthase; Plant pathogenic fungi

Novel findings on the copper catalysed oxidation of cysteine by Prof. L. Pecci; G. Montefoschi; G. Musci; D. Cavallini (pp. 355-367).

The oxidation of cysteine (RSH) has been studied by using O₂, ferricytochrome c (Cyt c) and nitro blue tetrazolium (NBT) as electron acceptors. The addition of 200μM Cu^II to a solution of 2mM cysteine, pH 7.4, produces an absorbance with a peak at 260 nm and a shoulder at 300 nm. Generation of a cuprous bis-cysteine complex (RS-Cu^I-SR) is responsible for this absorbance. In the absence of O₂ the absorbance is stable for long time while in the presence of air it vanishes slowly only when the cysteine excess is consumed. The neocuproine assay and the EPR analysis show that the metal remains reduced in the course of the oxidation of cysteine returning to the oxidised form at the end of reaction when all RSH has been oxidised to RSSR. Addition of Cu^II enhances the reduction rate of Cyt c and of NBT by cysteine also under anaerobiosis indicating the occurrence of a direct reduction of the acceptor by the complex. It is concluded that the cuprous bis-cysteine complex (RS-Cu^I-SR) is the catalytic species involved in the oxidation of cysteine. The novel finding of the stability of the complex together with the metal remaining in the reduced form during the oxidation suggest sulfur as the electron donor in the place of the metal ion.

Keywords: Amino acids; Cysteine; Copper catalysis; Cuprous complex

Role of feline maternal taurine nutrition in fetal cerebellar development: An immunohistochemical study by Dr. J. A. Sturman; P. Lu (pp. 369-377).

We report the effects of four levels of maternal dietary taurine on the cerebellum of 45-day gestation fetuses. As we have previously reported for newborn and 8-week-old kittens, maternal dietary taurine content has a profound effect also on fetal cerebellum. Fetuses from queens fed the lowest amount of taurine had the greatest density of granule cells, probably because of smallest brain size, and had a high proportion of morphological abnormalities. Somewhat surprising was the observation that the fetuses from the lowest maternal dietary taurine group had the highest proportion of taurine-positive granule cells. In addition, these results confirm the vulnerability of developing fetal brain to its intrauterine environment.

Keywords: Amino acids; Taurine; Cerebellum; Development; Immunohistochemistry

The amino acid composition of mammalian and bacterial cells by T. Okayasu; M. Ikeda; K. Akimoto; Dr. K. Sorimachi (pp. 379-391).

High performance liquid chromatography was used to analyze the amino acid composition of cells. A total of 17 amino acids was analyzed. This method was used to compare the amino acid compositions of the following combinations: primary culture and established cells, normal and transformed cells, mammalian and bacterial cells, andEscherichia coli andStaphylococcus aureus. The amino acid compositions of mammalian cells were similar, but the amino acid compositions ofEscherichia coli andStaphylococcus aureus differed not only from mammalian cells, but also from each other. It was concluded that amino acid composition is almost independent of cell establishment and cell transformation, and that the amino acid compositions of mammalian and bacterial cells differ. Thus, it is likely that changes in amino acid composition due to cell transformation or species differences between mammalian cells are negligible compared with the differences between mammalian and bacterial cells, which are more distantly related.

Keywords: Amino acids; HPLC; Mammalian cells; Bacterial cells

Sections

Personal tools

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.13, #3-4)

Sections

Personal tools

Local resources

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.13, #3-4)