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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.18, #4)

Interaction between the actions of taurine and angiotensin II by S. W. Schaffer; J. B. Lombardini; J. Azuma (pp. 305-318).

The amino acid, taurine, is an important nutrient found in very high concentration in excitable tissue. Cellular depletion of taurine has been linked to developmental defects, retinal damage, immundeficiency, impaired cellular growth and the development of a cardiomyopathy. These findings have encouraged the use of taurine in infant formula, nutritional supplements and energy promoting drinks. Nonetheless, the use of taurine as a drug to treat specific diseases has been limited. One disease that responds favorably to taurine therapy is congestive heart failure. In this review, we discuss three mechanisms that might underlie the beneficial effect of taurine in heart failure. First, taurine promotes natriuresis and diuresis, presumably through its osmoregulatory activity in the kidney, its modulation of atrial natriuretic factor secretion and its putative regulation of vasopressin release. However, it remains to be determined whether taurine treatment promotes salt and water excretion in humans with heart failure. Second, taurine mediates a modest positive inotropic effect by regulating [Na⁺]_i and Na⁺/Ca²⁺ exchanger flux. Although this effect of taurine has not been examined in human tissue, it is significant that it bypasses the major calcium transport defects found in the failing human heart. Third, taurine attenuates the actions of angiotensin II on Ca²⁺ transport, protein synthesis and angiotensin II signaling. Through this mechanism taurine would be expected to minimize many of the adverse actions of angiotensin II, including the induction of cardiac hypertrophy, volume overload and myocardial remodeling. Since the ACE inhibitors are the mainstay in the treatment of congestive heart failure, this action of taurine is probably very important.

Keywords: Keywords: Amino acids – Taurine – Angiotensin II – Congestive heart failure – Natriuresis – Diuresis – Osmoregulation – Calcium transport – Hypertrophy – Signal transduction

Polyamines and thiols in the cytoprotective effect of L-cysteine and L-methionine on carbon tetrachloride-induced hepatotoxicity by W. Chen; D. O. Kennedy; A. Kojima; I. Matsui-Yuasa (pp. 319-327).

The relationship between cellular glutathione (GSH), protein-SH levels, and lactate dehydrogenase (LDH), with respect to the effect of polyamines on the cytoprotective ability of L-cysteine and L-methionine, the most important components in the sulfur amino acid metabolic pathway, in carbon tetrachloride (CCl₄)-induced toxicity in isolated rat hepatocytes was studied. CCl₄ induced a LDH release and decreased cellular thiols and polyamines levels but treatment with L-cysteine and L-methionine reversed these decreases. Treating with methylglyoxal bis-(guanylhydrazone), MGBG, an irreversible inhibitor of S-adenosylmethionine decarboxylase, which is a key enzyme in spermidine and spermine biosynthesis, and therefore used to deplete cellular polyamines, prevented the protective effect of L-cysteine and L-methionine, but the addition of exogenous polyamines inhibited the influence of MGBG. These results suggest that the cytoprotective effect of L-cysteine and L-methionine in CCl₄-induced toxicity were via maintenance of cellular polyamines, GSH and protein-SH concentrations and prevention of LDH leakage.

Keywords: Keywords: Amino acids – L-Cysteine – L-Methionine – Polyamines – Glutathione – Protein sulfhydryl – Hepatocytes

Insertion of foreign epitopes in HBcAg: how to make the chimeric particle assemble by L. I. Karpenko; V. A. Ivanisenko; I. A. Pika; N. A. Chikaev; A. M. Eroshkin; T. A. Veremeiko; A. A. Ilyichev (pp. 329-337).

Hepatitis B core antigen is one of the most promising protein carriers of foreign epitopes of various human and animal pathogens. Chimeric HBcAg particles can be used as effective artificial immunogenes. Unfortunately, not all chimeric proteins are able to be particulated. The dependence of correct or incorrect folding of chimeric proteins on physical and chemical properties of inserts was studied with the help of ProAnalyst, SALIX and QSARPro computer programs. We have found that insertion of amino acids with high hydrophobicity, large volume, and high β-strand index prevent self-assembling chimeric proteins. These factors are most important for the C-termini of inserts. Recommendations for obtaining correct folding of chimeric HBcAg particles have been given.

Keywords: Keywords: Amino acids HBcAg – Foreign epitopes – Self-assemble – Core particles

Determination of L- and D-amino acids in foodstuffs by coupling of high-performance liquid chromatography with enzyme reactors by K. Voss; R. Galensa (pp. 339-352).

A technique is described for the enantiomeric determination of L- and D-amino acids. It works on the principle that the separation efficiency of high-performance liquid chromatography is coupled with the specificity of enzymes and the sensitivity of electrochemical detection. After separation on a lithium cation-exchange column the amino acids are converted into keto acids and hydrogen peroxide under catalyzation of L- or D-amino acid oxidase. Hydrogen peroxide is detected amperometrically. The method has been tested by the analysis of beer, port, sherry, wine and fruit juice.A main emphasis was put onto the determination of D-alanine which can serve as an indicator for bacterial contamination. It is shown that a coupling of HPLC with enzyme reactors is a suitable technique for the rapid detection of this marker.

Keywords: Keywords: Amino acids – Enzyme reactor – HPLC – D-Alanine – Microorganisms – Biosensor – Amino acid oxidase

Effects of testosterone and 17, β– estradiol on the polyamine metabolism in cultivated normal rat kidney epithelial cells by I. Jotova; C. Wang; A. Tabib; O. Dimitrov; U. Bachrach (pp. 353-361).

Ornithine decarboxylase (ODC) and diamine oxidase (DAO) are important enzymes involved in the metabolism of polyamines (putrescine, spermidine and spermine). The influence of testosterone (T) and 17, β– estradiol (E₂) on the activity of ODC and DAO was examined in cultivated normal rat kidney (NRK) epithelial cells. The results showed an increase in enzyme activities 4 hours or 12 hours after hormonal treatment. Both T and E₂ led to a significant increase (1.6-fold) in ODC protein level as compared to the controls. Cellular concentration of spermidine and spermine increased (2.2- and 2.6-fold respectively) 4 hours after T addition. A higher levels in concentrations of putrescine (1.4-fold) and spermine (1.5-fold) 12 hours after E₂ treatment were observed. These results suggest that the biosynthesis and terminal oxidation of the polyamines in NRK epithelial cells are androgen- and estrogen-mediated and depend on the hormonal sensitivity of the cells.

Keywords: Keywords: Amino acids – Polyamines – Testosterone – 17 β– Estradiol – Ornithine decarboxylase – Diamine oxidase

Studies of aminochrome toxicity in a mouse derived neuronal cell line: is this toxicity mediated via glutamate transmission? by C. Arriagada; A. Dagnino-Subiabre; P. Caviedes; J. Martin Armero; R. Caviedes; J. Segura-Aguilar (pp. 363-373).

Aminochrome was found to be toxic in a mouse-derived neuronal cell line (CNh). The effect was concentration dependent (10–150 μM). The issue whether aminochrome toxicity involves glutamate transmission was studied with several glutamate receptors antagonists. Incubation of the cells with aminochrome (150 μM) in the presence of 100 μM of the AMPA an-tagonist, NBQX resulted in an increase of cell survival, from 52 to 73%. However, this protective effect did not seem to be related to activation of ionotropic glutamate receptors since incubation of CNh cells with 200 μM of glutamate resulted in only 10% decrease of cell survival. However, NBQX was found to inhibit in vitro the autoxidation process. One hundred μM AP-5 did not have any effect on aminochrome toxicity. The toxic effect of aminochrome on CNh cells seems to be dependent of extracellular activation since addition of dicoumarol, a specific inhibitor of DT-diaphorase, did not affect that toxicity, which can be explained perhaps by a lack of a transport system for aminochrome into the CNh cells.

Keywords: Keywords: Amino acids – Dopamine – Toxicity – Aminochrome – Semiquinone – NMDA – AMPA – Kainate – Glutamate – Quinone – Excitotoxicity

Isozymic nature of spore coat-associated alanine racemase of Bacillus subtilis by K. Kanda-Nambu; Y. Yasuda; K. Tochikubo (pp. 375-387).

Spore coat-associated alanine racemase of Bacillus subtilis, which converts L-alanine to D-alanine, that is, the germinant to the competitive inhibitor, to regulate spore germination for survival of the organism under unfavorable growth conditions, was examined. The dormant spores, L-alanine-initiated germination of which is inhibited by diphenylamine, were used to characterize the enzyme in the native form because of its unextractablility from dormant spores. The presence of isozymes, Enz-I and Enz-II with Km for L-alanine of about 20 mM and 50 mM and optimum activity at around 40°C and 65°C, respectively, was proposed. The enzymes were selectively used depending on the L-alanine concentration and the temperature. The pH profiles of the activity (optimun at pH 9.0) and the stability (stable between pH 6–11 at 60°C) were similar, but Enz-II was more heat-stable than Enz-I and the denaturation curve demonstrated a two-domain structure for Enz-II. Sensitivity to D-penicillamine, hydroxylamine and HgCl₂ was similar between Enz-I and Enz-II, while that to D-cycloserine, L- and D-aminoethylphosphonic acid, monoiodoacetate and N-ethylmaleimide was different; HgCl₂ was the most effective inhibitor among these compounds.

Keywords: Keywords: Amino acid – Alanine racemase – Isozyme – Kinetics – Inhibitors –Bacillus subtilis– Spore coat

Taurine and pulmonary hemodynamics in sepsis by C. Chiarla; I. Giovannini; J. H. Siegel; G. Boldrini; M. Castagneto (pp. 389-397).

This study has been performed to characterize the relationship between changes in plasma taurine (TAU) and hemodynamic patterns in sepsis. Analysis of 249 plasma aminoacidograms (AA-grams) and associated measurements in a group of critically ill, mechanically ventilated septic patients, showed that decreases in TAU were significantly correlated with increases in pulmonary artery pressure and pulmonary vascular resistance, and with worsening of pulmonary dysfunction. All cases requiring posi-tive end-expiratory pressure greater than 10 cmH₂O had TAU lower than 50 μM/L. Low TAU was paralleled by decreases in other sulfur-containing AA, phosphoethanolamine, β-alanine, glutamate and aspartate, within a pattern of greater metabolic dysregulation. These data provide evidence of a link between severity of pulmonary dysfunction and reduced TAU availability in clinical sepsis. The implications relate also to the need for specific investigations of the clinical effect of exogenous TAU on proinflammatory mediator-induced pulmonary dysfunction.

Keywords: Keywords: Amino acids – Taurine – Sepsis – Pulmonary hemodynamics – Respiratory failure – Phosphoethanolamine

Androgenic sensitivity of polyamine-oxidizing enzyme activities in female rat tissues by V. Pavlov; O. Dimitrov (pp. 399-405).

Effects of testosterone (10 μg/100 g body weight) on polyamine-oxidizing enzyme activities in female rat uterus, liver and kidney were demonstrated. Testosterone-treated rats exhibited 2.07 fold (p < 0.002) higher uterine polyamine oxidase (PAO) activity and 1.93 fold (p < 0.02) higher diamine oxidase (DAO) activity, as compared to the controls. In the liver, testosterone caused an elevation in PAO (1.39 fold, p < 0.05), but not in DAO activity, whereas in kidney the hormone stimulated DAO (1.30 fold, p < 0.05), but not PAO activity. The effects observed suggest a possible role for testosterone in the modulation of polyamine levels in the female organs studied and especially in uterus.

Keywords: Keywords: Amino acids – Testosterone – Polyamine oxidase – Diamine oxidase – Female rat tissues

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.18, #4)