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107 records · Page 6Linked to original sources
PubMed1983

Increase in the phosphotransferase specific activity of purified Rous sarcoma virus pp60v-src protein after incubation with ATP plus Mg2+.

pp60v-src, the product of the Rous sarcoma virus src gene, was partially purified by immunoaffinity chromatography from extracts of Rous sarcoma virus-transformed field vole cells. Incubation of this preparation with ATP plus Mg2+ and subsequent repurification by chromatography on hexylamine-agarose resulted in a net increase in the specific activity of the src protein kinase. This increase in phosphotransferase activity was detected by using a variety of substrates including casein, tubulin, and a 34,000-dalton protein presumed to be an in vivo target substrate of pp60v-src. In all cases, the phosphorylation was at tyrosine residues, and the kinase activity was inhibited by preincubation of the enzyme with immunoglobulin G prepared from tumor-bearing rabbit sera. The implications of these results for the regulation and control of pp60v-src-associated kinase activity are discussed.

Adenosine Triphosphate↗
PubMed1986

Voltage-dependent aminoglycoside blockade of the sarcoplasmic reticulum K+ channel.

Single-channel conductance of the K+ channel from sarcoplasmic reticulum (SR) was reduced by aminoglycoside antibiotics such as neomycin and ribostamycin and also by n-hexylamine from either side of the membrane in a dose- and voltage-dependent manner. K+ channels were incorporated into an artificial phospholipid bilayer. This inhibition follows a single-site titration curve. The voltage dependence of the inhibition is explained by assuming that these drugs bind to the open state of a single channel on one site located approximately 40% of the way through the membrane from the cis side (the side to which SR vesicles are added) when drugs are added to the cis side and bind on another site located approximately 40% of the way through the membrane from the trans side (the opposite side to the cis side) when drugs are added to the trans side.

Amines↗
PubMed1995

Stability, specific binding activity, and plasma concentration in mice of an oligodeoxynucleotide modified at 5'-terminal with poly(ethylene glycol).

Oligodeoxynucleotide (ODN) composed of 15 nucleotides was modified at 5'-terminal phosphate with hexylamine linker and chemically activated poly(ethylene glycol). This derivative showed improved characteristics in terms of enzymatic stability, binding activity, and in vivo retention in mouse. The data are discussed in comparison with those of corresponding unmodified and phosphorothioate ODNs.

Animals↗
PubMed1997

Modulation of GABA receptors expressed in Xenopus oocytes by 13-L-hydroxylinoleic acid and food additives.

To study the effects of 13-L-hydroxylinoleic acid (LOH) and food additives on gamma-aminobutyric acid (GABA) receptors, ionotropic GABA receptors were expressed in Xenopus oocytes by injecting mRNAs prepared from rat whole brain. LOH, which was prepared by reduction of 13-L-hydroperoxylinoleic acid (LOOH), inhibited the response of GABA receptors in the presence of high concentrations of GABA. LOH also inhibited nicotinic acetylcholine, glycine, and kainate receptors, while it had little effect on NMDA receptors expressed in Xenopus oocytes. However, LOH potentiated the response of GABA receptors as well as LOOH in the presence of low concentrations of GABA, possibly increasing the affinity of GABA for the receptors, while linoleic acid did not. Since some modification of the compounds seemed to change their effects on GABA receptors, the responses of GABA receptors elicited by 10 microM GABA were measured in the presence of compounds with various kinds of functional groups or the structural isomers of pentanol. Potentiation of GABA receptors depended strongly on the species of functional groups and also depended on the structure of the isomers. Then effects of various kinds of food additives on GABA receptors were also examined; perfumes such as alcohols or esters potentiated the responses strongly, while hexylamine, nicotinamide, or caffeine inhibited the responses, mainly in a competitive manner, and vanillin inhibited the responses noncompetitively. These results suggest the possibility that production of LOOH and LOH, or intake of much of some food additives, modulates the neural transmission in the brain, especially through ionotropic GABA receptors and changes the frame of the human mind, as alcohol or tobacco does.

Animals↗
PubMed1999

Purification and characterization of methylamine oxidase induced in Aspergillus niger AKU 3302.

Crude extract of Aspergillus niger AKU 3302 mycelia incubated with methylamine showed a single amine oxidase activity band in a developed polyacrylamide gel that weakly cross-reacted with the antibody against a copper/topa quinone-containing amine oxidase (AO-II) from the same strain induced by n-butylamine. Since the organism cannot grow on methylamine and the already known quinoprotein amine oxidases of the organism cannot catalyze oxidation of methylamine, the organism was forced to produce another enzyme that could oxidize methylamine when the mycelia were incubated with methylamine. The enzyme was separated and purified from the already known two quinoprotein amine oxidases formed in the same mycelia. The purified enzyme showed a sharp symmetric sedimentation peak in analytical ultracentrifugation showing S20,w0 of 6.5s. The molecular mass of 133 kDa estimated by gel chromatography and 66.6 kDa found by SDS-PAGE confirmed the dimeric structure of the enzyme. The purified enzyme was pink in color with an absorption maximum at 494 nm. The enzyme readily oxidized methylamine, n-hexylamine, and n-butylamine, but not benzylamine, histamine, or tyramine, favorite substrates for the already known two quinoprotein amine oxidases. Inactivation by carbonyl reagents and copper chelators suggested the presence of a copper/topa quinone cofactor. Spectrophotometric titration by p-nitrophenylhydrazine showed one reactive carbonyl group per subunit and redox-cyclic quinone staining confirmed the presence of a quinone cofactor. pH-dependent shift of the absorption spectrum of the enzyme-p-nitrophenylhydrazone (469 nm at neutral to 577 nm at alkaline pH) supported the identity of the cofactor with topaquinone. Nothern blot analysis indicated that the methylamine oxidase encoding gene is largely different from the already known amine oxidase in the organism.

Amino Acid Sequence↗
PubMed1995

Inhibition of copper/quinoprotein amine oxidases from Aspergillus niger by benzophenanthridine alkaloids.

Inhibition of copper/quinoprotein amine oxidases (EC 1.4.3.6), AO-I (dimer 2 x 75 kDa) and AO-II (monomer 80 kDa), from the fungus Aspergillus niger by benzophenanthridine alkaloids sanguinarine, chelerythrine, and fagaronine were studied. For both amine oxidases the alkaloids showed reversible noncompetitive inhibition of n-hexylamine oxidation with Ki 0.6, 0.9 and 2.8 mM for sanguinarine, chelerythrine, and fagaronine, respectively. The values of the inhibition constants corresponded to pKR+ values for the iminium ion/pseudobase equilibrium of the alkaloids. Since thio-compounds protected the enzymes against this inhibition, the inhibition effect was ascribed to the interaction with a sulfhydryl group essential for the enzymatic activity.

Alkaloids↗
PubMed1996

Comparison of kinetic properties between plant and fungal amine oxidases.

Kinetic properties of novel amine oxidases isolated from a mold Aspergillus niger AKU 3302 were compared to those of typical plant amine oxidase from pea seedling (EC 1.4.3.6). Pea amine oxidase showed highest affinity with diamines, such as putrescine and cadaverine, while fungal enzymes oxidized preferably n-hexylamine and tyramine. All enzymes were inhibited by carbonyl reagents, copper chelating agents, some substrate analogs and alkaloids, but there were quite significant differences in the sensitivity and inhibition modes. Aminoguanidine, which strongly inhibited pea amine oxidases showed only little effect on fungal enzymes. Substrate analogs such as 1.5-diamino-3-pentanone and 1-amino-3-phenyl-3-propanone, which were potent competitive inhibitors of pea amine oxidases, inhibited fungal enzymes much more weakly and non competitively. Also various alkaloids behaving as competitive inhibitors of pea amine oxidase inhibited the fungal enzymes non competitively. Very surprising was the potent inhibition of fungal enzymes by artificial substrates of pea amine oxidases, E- and Z-1,4-diamino-2-butene. The relationships between the different inhibition modes and possible binding at the active site are discussed.

Amine Oxidase (Copper-Containing)↗
PubMed1976

[On the mode of action of heptaminol (author's transl)].

The effect of heptaminol, an aliphatic amine with an alcoholic group on carbon 2, on sympathetic nerves and on isolated chromaffine granules was infestigated. In cats, heptaminol caused long-lasting, dose-dependent pressor effects accompanied by tachycardia and contractions of the nictitating membrane. In comparison with tyramine, heptaminol was 100 times less potent in increasing blood pressure and 10 times less effective in inducing contractions of the nictitating membrane. The rise in blood pressure as well as tachycardia and contraction of the nictitating membrane were diminished by cocaine. After pretreatment with cocaine, heptaminol in high doses caused short-lasting depressor effects. Also in rats the pressor effect of heptaminol was weaker but of longer duration than that of tyramine. The dose-response curve was depressed by pretreatment with reserpine. The tachycardia induced by heptaminol was markedly diminished after pretreatment with reserpine. After repeated injections heptaminol reduced the norepinephrine content of the rat heart by 20-40%, Tyramine and hexylamine were more effective than heptaminol in depleting the norepinephrine stores of the heart (50-60%). In fluorescence microscopic investigations on sympathetic nerves (rat iris) depleted of norepinephrine by reserpine, the uptake of alpha-methylnorepinephrine could be inhibited or prevented by heptaminol. The spontaneous release of catecholamines from isolated bovine chromaffine granules was enhanced (+30%) by heptaminol or methamphetamine in high concentrations. In lower concentrations, however, both drugs reduced the uptake of 14C-epinephrine in isolated medullary granules by 20-40%. In addition a non-specific papaverine-like spasmolytic effect of heptaminol could be demonstrated. The results suggest that heptaminol exerts its pharmacological action by interfering with release and uptake of norepinephrine.

Adrenal Medulla↗
PubMedDate not supplied

Capillary gas chromatographic determination with electron capture detector of beta-propiolactone in biological materials.

A method has been developed for the determination of beta-propiolactone by derivatizing it to the volatile N-hexyl-3-heptafluorobutanoyloxypropanamide, which can be separated and identified by a capillary CP-Sil 8 column, and detected by an electron capture detector (ECD). First, beta-propiolactone is reacted with N-hexylamine to yield N-hexyl-3-hydroxypropanamide. The fluorobutanoyl ester derivative is next prepared by using heptafluorobutyric acid anhydride in the presence of trimethylamine. The method is very sensitive, simple, and specific, and can be used to detect and quantitate residual beta-propiolactone in lyophilized biological materials. The limit of detection is 0.2 ppm beta-propiolactone in a 50 mg sample; however, because of variability at low levels, the limit of quantitation is 1 ppm. Detector response was linear for 2-500 mg beta-propiolactone. Recoveries were 98% or greater from lyophilized vaccines spiked at the 2-20 ppm level. No side products or interference peaks were observed in the derivatization reaction.

Chromatography, Gas↗
PubMed1990

Ligand interactions with the kringle 5 domain of plasminogen. A study by 1H NMR spectroscopy.

The binding of small molecules to the kringle 5 domain fragment of human plasminogen has been investigated by 1H NMR spectroscopy at 300 MHz. The compounds tested as potential ligands include L-arginine, L-lysine, and a number of aliphatic and aromatic analogs of similar size but different ionic charge configurations. Ligand/kringle 5 association constant (Ka) values were obtained from ligand titration experiments at 22 degrees C, pH 7.2. Neither L-arginine nor N alpha-acetyl-L-arginine and N alpha-acetyl-L-arginine methyl ester bind measurably to kringle 5 (Ka approximately less than 0.05 mM-1). In contrast, binding of hexylamine or epsilon-aminocaproic acid (epsilon ACA) is favored (Ka approximately 2.9 and 10.5 mM-1, respectively). Benzamidine and p-benzylaminesulfonic acid associate with kringle 5 with similar affinities (Ka approximately 3.4 and 2.2 mM-1, respectively) while benzylamine binds about twice as tightly (Ka approximately 6.3 mM-1). The higher affinities toward both benzylamine and epsilon ACA indicate that a free carboxylate group is not, by itself, a main determinant of ligand-binding to kringle 5. The experiments also reveal a definite affinity for L-arginine methyl ester, L-lysine, and N alpha-acetyl-L-lysine methyl ester. It is suggested that, although weak (0.1 approximately less than Ka approximately less than 0.6 mM-1), these interactions could be of physiological relevance in the context of plasminogen binding to the fibrin clot. Ligand-induced shifts of kringle 5 proton resonances indicate that the Trp25, His33, Tyr50, Trp62, and Tyr72 (kringle numbering convention) side chains form or neighbor the kringle 5-binding site. Benzamidine-kringle 5 magnetization transfer (Overhauser) experiments verify a close proximity of the bound ligand to these aromatic groups. A model of the binding site is proposed in which the above residues interact closely with each other and define a lipophilic surface which is accessible to the free ligand.

Amino Acid Sequence↗
PubMed1988

Comparative carcinogenesis by nitrosomethylalkylamines in Syrian hamsters.

Six homologous nitrosomethyl-n-alkylamines, from n-propyl (C-3) to n-octyl (C-8), were administered by gavage to groups of 12 male and 12 female Syrian golden hamsters as solutions in corn oil:ethyl acetate (2:1). The solutions of C-8 to C-4 were equimolar; nitrosomethyl-n-butylamine (C-4) and nitrosomethyl-n-propylamine (C-3) were given at a lower concentration. Treatment with 0.2 ml of solution lasted 23 to 50 wk, being stopped when several hamsters had died. Additional groups of hamsters were treated similarly with nitrosomethylaniline and nitrosomethylcyclohexylamine. Excepting hamsters given the latter, treated animals had reduced survival compared with controls. The incidence of tumors in hamsters given nitrosomethylaniline and nitrosomethylcyclohexylamine was low and occurred in the liver, lungs, and spleen. Hamsters treated with nitrosomethyl-n-propylamine and nitrosomethyl-n-butylamine suffered the greatest decrease in survival. Potency judged by this criterion decreased as the size of the molecule increased in the homologous series. Virtually all of these treated hamsters died with tumors not seen in controls. These tumors, which were common in hamsters given all of the nitrosomethyl-n-alkylamines, were in the liver, lung, forestomach, and nasal mucosa, but the incidences varied somewhat between the compounds and between sexes. Bladder tumors were seen only in hamsters given nitrosamines containing even numbers of carbon atoms in the chain, namely, nitrosomethyl-n-hexylamine and nitrosomethyl-n-octylamine.

Animals↗
PubMed1980

T4 RNA ligase as a nucleic acid synthesis and modification reagent.

Oligodeoxyribonucleotides corresponding to portions of the recognition sequence and analogues thereof of the Eco RI restriction endonuclease have been synthesized using T4 RNA ligase. The successive addition of deoxyribonucleoside-3',5'-bisphosphates to preformed deoxyoligomers allowed stepwise oligodeoxyribonucleotide synthesis. Single strand deoxyoligomers were also joined to one another by the enzyme. In addition, biotin, and fluorophore tetramethylrhodamine, and hexylamine have been added to RNA via an ATP-independent RNA ligase reaction using their ADP adducts as substrates. When the beta-substituent on ADP is a good leaving group, e.g. p-nitrophenol or 4-methylumbelliferol, the RNA product is the 2'-(3')-cyclicphosphate derivative.

DNA Restriction Enzymes↗
PubMed1982

A sensitive assay for mutagenic activity of N-nitrosamines and its use for detection of modulators of the mutagenicity.

By carrying out the pre-incubation of bacteria with N-nitrosamines under acidic conditions, the mutagenicity of N-nitrosodimethylamine on Salmonella TA100 and E. coli WP2 try, hcr was detected with increased sensitivity, compared to usual assays in neutral buffers. Using this modified assay system, compounds have been screened for their modulating effects on N-nitrosamine-mediated mutagenesis and the following were found to be inhibitors: cysteine, cysteamine, bisulfite, n-propylamine, n-butylamine, n-hexylamine, n-octylamine, n-nonylamine, serotonine, tryptamine, epinephrine, norepinephrine and oleic acid. The mechanisms of inhibition are discussed.

Amines↗
PubMed1983

[Effects of oxygen and drugs on monoamine oxidase in the dog liver].

The substrate specificity and effects of oxygen concentration and inhibitors on dog liver mitochondrial monoamine oxidase were investigated. MAO activity was determined by measuring oxygen uptake by Warburg's manometer. Dog liver mitochondrial MAO oxidized tyramine most strongly, but oxidation of serotonin, benzylamine and beta-phenylethylamine by this enzyme was found to be very weak, showing less than 30% that of tyramine oxidation. Clorgyline and harmine showed slight inhibition of oxidation of all substrates used in this experiment; however, deprenyl and pargyline strongly inhibited the oxidation of tyramine. The affinity of MAO towards oxygen was found to be strongest with benzylamine as substrate and weakest with hexylamine, and it was intermediate with serotonin. The differences in affinities towards oxygen of this enzyme with various substrates were not changed with any MAO inhibitors added to the reaction mixture. These results suggest that MAO in dog liver mitochondria belongs to type B MAO because of the characteristic behavior of this enzyme to inhibitors. It is suggested that the multiplicity of MAO, which is characterized by substrate and inhibitor specificities, is different from the multiplicity, which is characterized by the affinities towards oxygen.

Animals↗
PubMed1993

Reaction of lysyl oxidase with trans-2-phenylcyclopropylamine.

trans-2-Phenylcyclopropylamine hydrochloride (tranylcypromine; TCP) was found to be both an inhibitor and a substrate of lysyl oxidase, the enzyme which oxidizes peptidyl lysine in elastin and collagen to initiate cross-linking in these proteins. The reaction of TCP with this enzyme was further characterized in view of the potential interference that chronic administration of this antidepressant compound may exert on the development and repair of connective tissues. In contrast to the irreversible and/or competitive inhibitors of lysyl oxidase previously described, TCP noncompetitively and reversibly inhibited the oxidation of both alkylamine and elastin substrates with Ki values of 386 and 375 microM, respectively. The noncompetitive mode of interaction affected the accessibility of the active site to productive amine substrates since the reductive trapping of n-hexylamine to lysyl oxidase was largely prevented by the presence of TCP. It was of additional interest that lysyl oxidase catalyzed a limited degree of conversion of TCP to cinnamaldehyde accompanied by the production of hydrogen peroxide. The lack of significant incorporation of protein-bound tritium accompanying reduction of the enzyme-TCP complex with [3H]NaBH4 argued against the formation of a Schiff base between the enzyme and the cinnamaldehyde product as the basis of the inhibitory effect. Spectral evidence was also obtained for an additional interaction between TCP and lysyl oxidase that was independent of the inhibitory effect of TCP. Cyclopropylamine, lacking the benzene moiety of TCP, inhibited lysyl oxidase irreversibly and competitively, and was not a substrate, pointing toward a defining role for the benzene moiety in the interaction of TCP with lysyl oxidase.

Animals↗