Showing papers on "Agmatine published in 1987"

L-arginine is required for expression of the activated macrophage effector mechanism causing selective metabolic inhibition in target cells.

Abstract: L-Arginine is required for expression of the activated macrophage cytotoxic effector mechanism that causes inhibition of mitochondrial respiration, aconitase activity, and DNA synthesis in tumor target cells. This effector mechanism is active in the presence of L-arginine even when the cocultivation medium lacks all other amino acids and serum. Cytotoxic activated macrophage-induced inhibition of mitochondrial respiration in target cells is proportional to the concentration of L-arginine in the medium. L-Arginine must be present during the cocultivation period. Pretreatment of cytotoxic activated macrophages with L-arginine or posttreatment of the target cells after cocultivation is not effective. D-Arginine does not substitute for L-arginine and at high concentrations is a competitive inhibitor of the L-arginine-dependent effector mechanism. Other analogues that could not replace L-arginine include agmatine, argininic acid, arginine hydroxamate, and tosyl-L-arginine methyl ester. L-homoarginine, however, can effectively substitute for L-arginine. NG-monomethyl-L-arginine is a potent competitive inhibitor of this effector mechanism. High concentrations of lipopolysaccharide do not reverse inhibition of the L-arginine-dependent effector mechanism by NG-monomethyl-L-arginine. However, inhibition of the effector mechanism by NG-monomethyl-L-arginine can be overridden by increasing the concentration of L-arginine in the culture medium. We compared NGNG-dimethyl-L-arginine and NGN1G-dimethyl-L-arginine with NG-monomethyl-L-arginine as inhibitors of the L-arginine-dependent effector mechanism. The results show that the inhibitory effect of these guanidino methylated derivatives of L-arginine is highly determined by structure. Guanidine is a weak competitive inhibitor of the L-arginine-dependent effector mechanism. The requirement for L-arginine does not appear to be for protein synthesis, creatine biosynthesis, polyamine biosynthesis, or ADP ribosylation reactions. Bacterial lipopolysaccharide is effective as a second signal only when the cocultivation medium contains L-arginine, and this strict L-arginine dependency is not overridden by increasing the concentration of lipopolysaccharide. Bovine liver arginase, by competing for L-arginine in the cocultivation medium, inhibits the L-arginine-dependent activated macrophage cytotoxic effector mechanism.

Enhancement of choleragen ADP-ribosyltransferase activities by guanyl nucleotides and a 19-kDa membrane protein

Abstract: Choleragen activates adenylate cyclase by catalyzing, in the presence of NAD, the ADP-ribosylation of Gs alpha, the stimulatory guanyl nucleotide-binding protein of the cyclase system. Kahn and Gilman [Kahn, R. A. & Gilman, A. G. (1986) J. Biol. Chem. 261, 7906-7911] identified another guanyl nucleotide-binding protein termed ADP-ribosylation factor (ARF) that stimulated this reaction. It was proposed that the toxin substrate is an ARF-Gs alpha complex and that ARF may have a physiological role in regulation of Gs alpha activity. We have found that purified ARF from bovine brain enhances not only the ADP-ribosylation of Gs alpha but also Gs alpha-independent choleragen-catalyzed reactions. These are (i) ADP-ribosylation of agmatine, a low molecular weight guanidino compound; (ii) ADP-ribosylation of several proteins unrelated to Gs alpha; and (iii) auto-ADP-ribosylation of the toxin A1 peptide. These reactions, as well as the ADP-ribosylation of ARF itself, were stimulated by GTP or stable GTP analogues such as guanyl-5'-yl imido-beta gamma-diphosphate and guanosine 5'-O-[gamma-thio]triphosphate; GDP and guanosine 5'-O-[beta-thio]diphosphate were inactive. These observations are consistent with the conclusion that ARF interacts directly with the A subunit of choleragen in a GTP-dependent fashion thereby enhancing catalytic activity manifest as transfer of ADP-ribose to Gs alpha and other proteins, to the toxin A1 peptide, or to agmatine. It is tempting to speculate that ARF may be involved in regulating one or another of the ADP-ribosyltransferases found in animal cells.

Agmatine as a Potential Index for Freshness of Common Squid (Todarodes pacificus)

Abstract: Changes in amines (tyramine, putrescine, cadaverine, agmatine, and tryptamine) were examined in the muscle of common squid during storage at 0°C, 3.5°C, and 15°C. Agmatine appeared to be most useful as a potential index for freshness of common squid. Agmatine was detected in small amounts even in the fresh muscle and the concentration increased with storage time, exceeding 30 mg/100g at the stage of initial decomposition and reached the level of 40 mg/100g at the stage of advanced decomposition. Putrescine was detected in small amounts (less than 1 mg/100g) at the stage of initial decomposition and increased rapidly at the stage of advanced decomposition. This amine might be involved in the putrid smell. The pH values became higher at the stage of initial decomposition.

Arginine decarboxylase inhibitors reduce the capacity of Trypanosoma cruzi to infect and multiply in mammalian host cells.

Abstract: The capacity of blood (trypomastigote) forms of Trypanosoma cruzi to infect mouse peritoneal macrophages or rat heart myoblasts in vitro was inhibited by treatment of the trypomastigotes with DL-alpha-difluoromethylarginine (F2Me Arg), monofluoromethylagmatine, or (E)-alpha-monofluoromethyl-3-4-dehydroarginine--all irreversible inhibitors of arginine decarboxylase Similar results were obtained when F2MeArg-treated parasites were incubated with rat heart myoblasts The inhibitory effects were characterized by marked reductions in both the proportion of infected cells and the number of parasites per 100 host cells The concentrations of the arginine decarboxylase inhibitors that affected infectivity had no detectable effect on either the concentration or motility of the parasite and, therefore, could not have affected the collision frequency F2MeArg appeared to inhibit the ability of T cruzi to penetrate the host cells since the drug had no significant effect on the extent of parasite binding to the surface of the host cells The inhibitory effect of F2MeArg was markedly reduced or abrogated in the presence of either agmatine or putrescine, as would have been expected if F2MeArg acted by inhibiting arginine decarboxylase Addition of F2MeArg to macrophage or myoblast cultures immediately after infection or at a time when virtually all of the intracellular parasites had transformed into the multiplicative amastigote form, resulted in a markedly reduced parasite growth rate This effect was also prevented by exogenous agmatine These results indicate the importance of polyamines and polyamine biosynthesis in the following two important functions of T cruzi: invasion of host cells and intracellular multiplication Furthermore, concentrations of the inhibitors tested that affected the parasite did not alter the viability of the host cells, the cellular density of the cultures, or the ability of uninfected myoblasts to grow Thus, arginine decarboxylase inhibitors may have a potential application in chemotherapy against T cruzi infection

Catalytic irreversible inhibition of bacterial and plant arginine decarboxylase activities by novel substrate and product analogues.

Abstract: Arginine decarboxylase (ADC) activity from Escherichia coli and two plant species (oats and barley) was inhibited by five new substrate (arginine) and product (agmatine) analogues. The five compounds, (E)-alpha-monofluoromethyldehydroarginine (delta-MFMA), alpha-monofluoromethylarginine (MFMA), alpha-monofluoromethylagatine (FMA), alpha-ethynylagmatine (EA) and alpha-allenylagmatine (AA), were all more potent inhibitors of ADC activity than was alpha-difluoromethylarginine (DFMA), the only irreversible inhibitor of this enzyme described previously. The inhibition caused by the five compounds was apparently enzyme-activated and irreversible, since the loss of enzyme activity followed pseudo-first-order kinetics, was time-dependent, the natural substrate of ADC (arginine) blocked the effects of the inhibitors, and the inhibition remained after chromatography of inhibited ADC on Sephadex G-25 or on overnight dialysis of the enzyme. DFMA, FMA, delta-MFMA and MFMA were effective at very low concentrations (10 nM-10 microM) at inhibiting ADC activity in growing E. coli. FMA was also shown to deplete putrescine effectively in E. coli, particularly when combined with an inhibitor of ornithine decarboxylase, alpha-monofluoromethyl-putrescine. The potential uses of the compounds for the study of the role of polyamine biosynthesis in bacteria and plants is discussed.

Biosynthesis of polyamines in ornithine decarboxylase, arginine decarboxylase, and agmatine ureohydrolase deletion mutants of Escherichia coli strain K-12.

Abstract: Escherichia coli K-12 mutants that carry deletions in their genes for ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) (speC), arginine decarboxylase (L-arginine carboxy-lyase, EC 4.1.1.19) (speA), and agmatine ureohydrolase (agmatinase or agmatine amidinohydrolase, EC 3.5.3.11) (speB) can still synthesize very small amounts of putrescine and spermidine. The putrescine concentration in these mutants was found to be 1/2500th that in spe+ cells. The pathway of putrescine synthesis appears to be through the biodegradative arginine decarboxylase, which converts arginine to agmatine, in combination with a low agmatine ureohydrolase activity--1/2000th that in spe+ strains. These results suggest that even such low levels of polyamines permit a low level of protein synthesis. Evidence is presented that the polyamine requirement for the growth of the polyamine-dependent speAB, speC deletion mutants, which are also streptomycin resistant, is not due to a decreased ability to synthesize polyamines.

An NAD: Cysteine ADP-Ribosyltransferase Is Present in Human Erythrocytes

Abstract: A novel enzymatic activity, i.e., the catalysis of the formation of ADP-ribosylcysteine, was found in the cytosol of human erythrocytes. The NAD:cysteine ADP-ribosyltransferase was partially purified by sequential chromatographic steps on phenyl-Sepharose, phosphocellulose, and Sepharose CL-6B. The enzyme has an apparent molecular weight of 27,000 +/- 3,000, as determined by gel permeation. The formation of ADP-ribosylcysteine was associated with the stoichiometric release of nicotinamide from NAD. The enzyme was found to be highly specific toward cysteine and cysteine methyl ester as ADP-ribose acceptors. S-Benzoyl-L-cysteine, cystine, histidine, glutamic acid, arginine, arginine methyl ester, and agmatine were ineffective as acceptors for this enzyme.

Polyamine contents and amino acid decarboxylation activities of extremely halophilic archaebacteria and some eubacteria

Abstract: An extremely halophilic archaebacterium Halobacterium cutirubrum was demonstrated to be devoid of any polyamine except agmatine when grown in a synthetic medium with no exogenous polyamines. Decarboxylation activities of homoarginine and canavanine as well as of arginine were shown to be present in cell lysates of 5 strains of extreme halophiles examined. H. halobium R1 was shown to have an additional pathway to synthesize agmatine from glutamic acid.

Analysis of enzyme kinetics by using integrated rate equations. Arginine decarboxylase.

Abstract: We have used an integrated rate equation to analyse the reaction catalysed by the inducible arginine decarboxylase from Escherichia coli B. The stoichiometry Arginine----agmatine + CO2 is the simplest of the multiple-substrate/multiple-product cases. Twenty-one time courses were carried out at various initial concentrations of arginine and agmatine, and were then fitted to the integrated equation by using appropriate analytical procedures. Values were obtained for six of the seven possible kinetic constants, corresponding to kcat, KArg, the terms for competitive inhibition by agmatine, by CO2 and by agmatine and CO2 together, and the term for uncompetitive inhibition by agmatine. The uncompetitive constant for CO2 was indeterminate. Our results indicate that it is both practical and experimentally economical to obtain kinetic constants from full time courses.

Evidence for an involvement of membrane lipids in the control of neuronal nicotinic receptor function using bungarotoxin II-S1.

Abstract: Previous work has shown that a toxin fraction, bungarotoxin (BGT) II-S1, isolated from Bungarus multicinctus venom could inhibit nicotinic receptor-mediated function. Experimental evidence suggested that this effect of the toxin might be due to a direct interaction of the toxin at the acetylcholine binding site and/or to its phospholipase activity. The toxin's enzymic activity has been further characterized; it has phospholipase activity of the A2 type with a Vmax of 12 pmol/min/ng protein and a Km of 300 microM. Phospholipases can produce their effects on a tissue through a variety of mechanisms including the disruption of important lipid protein bonds or the production of free fatty acids which interact with the tissue. To test for this latter possibility, various concentrations of fatty acid-free bovine serum albumin were added to the incubation medium. Fatty acid-free bovine serum albumin partially reversed the inhibition of carbachol-stimulated 1-[1,2-3H(N)]amino-4-guanidobutane ([3H]agmatine) uptake (used as a measure of ion flux) into the ganglion produced by BGT II-S1 (1.0 microM). In an attempt to determine which fatty acids might be responsible for this effect, various fatty acids were added to the incubation medium and their effect on nicotinic receptor-mediated [3H]agmatine uptake determined. Arachidonic acid decreased amine uptake by approximately 50% over the control carbachol-stimulated uptake; linoleic and oleic acid, on the other hand, did not significantly affect the response. This observation could imply that arachidonic acid is the fatty acid produced by the action of BGT II-S1 on the tissue to mediate the toxin's inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine decarboxylase is a component activity of the multifunctional enzyme putrescine synthase in cucumber seedlings

Abstract: A homogenous PreParation of Putrescine synthase, the versatile multifunctional enzyme involved in agmatine →Putrescine conversion inCucumis sativus was found to catalyze enzymatic decarboxylation of arginine also. Similarly, the Purified arginine decarboxylase mediated the comPonent as well as the comPlete set of couPled reactions harboured by Putrescine synthase. Both the enzyme PreParations exhibited identical electroPhoretic and chromatograPhic behaviour and were immunologically indistinguishable. All the enzymic activities are stabilized concurrently by feeding arginine to the intact seedlings. Therefore, it is concluded that the multifunctional Putrescine synthase inCucumis sativus seedlings also harbours arginine decarboxylase activity unlike its counterPart inLathyrus sativus.

Enzyme-Activated Irreversible Inhibition of Bacterial and Plant Arginine Decarboxylase, by Either Substrate or Product Analogues

Abstract: A regiospecific guanidination of ornithine and put re seine analogues, inhibitors of ornithine decarboxylase (ODC), afforded the corresponding arginine and agmatine analogues. These new compounds were found to be very potent time-dependent, irreversible inhibitors of arginine decarboxylase from E. coli and plants. The potential use of these compounds is discussed.