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PubMed1989

Potent and selective inactivation of cysteine proteinases with N-peptidyl-O-acyl hydroxylamines.

A series of N-peptidyl-O-acyl hydroxylamines was synthesized and tested as inactivators of cysteine proteinases. Depending on the structure of the peptidyl residue of the inhibitors, rapid and complete irreversible inactivation of the lysosomal cathepsins, B, L and S, may be achieved. The most effective inhibitors display second-order rate constants of the inactivation in the range 10(5)-10(6) M-1.s-1. By contrast, the activity of the aminoendopeptidase cathepsin H is only negligibly affected by the N-terminal-protected peptidyl inhibitors.

Amino Acid Sequence↗
PubMed2000

Direct binding of hydroxylamine to the heme iron of Arthromyces ramosus peroxidase. Substrate analogue that inhibits compound I formation in a competetive manner.

The interaction of hydroxylamine (HA) with Arthromyces ramosus peroxidase (ARP) was investigated by kinetic, spectroscopic, and x-ray crystallographic techniques. HA inhibited the reaction of native ARP with H(2)O(2) in a competitive manner. Electron absorption and resonance Raman spectroscopic studies indicated that pentacoordinate high spin species of native ARP are converted to hexacoordinate low spin species upon the addition of HA, strongly suggesting the occurrence of a direct interaction of HA with ARP heme iron. Kinetic analysis exhibited that the apparent dissociation constant is 6.2 mm at pH 7.0 and that only one HA molecule likely binds to the vicinity of the heme. pH dependence of HA binding suggested that the nitrogen atom of HA could be involved in the interaction with the heme iron. X-ray crystallographic analysis of ARP in complex with HA at 2.0 A resolution revealed that the electron density ascribed to HA is located in the distal pocket between the heme iron and the distal His(56). HA seems to directly interact with the heme iron but is too far away to interact with Arg(52). In HA, it is likely that the nitrogen atom is coordinated to the heme iron and that hydroxyl group is hydrogen bonded to the distal His(56).

Binding Sites↗
PubMed1988

Reaction of N-hydroxylamine and N-acetoxy derivatives of 2-amino-3-methylimidazolo[4,5-f]quinoline with DNA. Synthesis and identification of N-(deoxyguanosin-8-yl)-IQ.

The N-hydroxylamine of the carcinogen 2-amino-3-methylimidazolo[4,5-f]quinoline (IQ) covalently bound to calf thymus DNA at pH 7, and the binding was 11% higher under acidic conditions (pH 5). The extent of N-hydroxy-IQ binding to single-stranded polynucleotides at neutral pH was in the following order: polyguanylic acid much greater than polyadenylic acid greater than polycytidylic acid = polyuridylic acid. The binding of the carcinogen to DNA, polyguanylic acid and polyadenylic acid at neutral pH was enhanced 6-, 4- and 2-fold respectively by the presumed in situ formation of N-acetoxy-IQ from N-hydroxy-IQ and acetic anhydride. N-(Deoxyguanosin-8-yl)-IQ was synthesized by reaction at pH 7 of N-acetoxy-IQ (formed in situ with N-hydroxy-IQ and acetic anhydride) with deoxyguanosine and the structure characterized by NMR, mass spectral and UV absorption spectral analyses. Reverse phase HPLC of enzymatically hydrolyzed DNA which had been reacted with N-hydroxy-IQ in vitro showed a major adduct which was chromatographically identical to synthetic N-(deoxyguanosin-8-yl)-IQ. In addition, N-acetoxy-IQ, generated chemically by acetic anhydride or enzymatically with mammalian acetyltransferase, formed one major adduct with DNA which was chromatographically identical to the synthetic N-(deoxyguanosin-8-yl)-IQ. The results indicate that N-hydroxy-IQ and N-acetoxy-IQ react with DNA forming primarily the N-(deoxyguanosin-8-yl)-IQ adduct.

Acetates↗
PubMed2004

The use of N-t-butyl hydroxylamine for radioprotection in cultured cells and mice.

Exposure of cells to ionizing radiation leads to formation of reactive oxygen species (ROS) that are associated with radiation-induced cytotoxicity. Therefore, compounds that scavenge ROS may confer radioprotective effects. Recently, it has been shown that the decomposition product of the spin-trapping agent alpha-phenyl-N-t-butylnitrone (PBN), N-t-butyl hydroxylamine (NtBHA), mimics PBN and is much more potent in delaying ROS-associated senescence. We investigated the protective role of NtBHA against ionizing radiation in U937 cells and mice. Viability and cellular oxidative damage reflected by lipid peroxidation, oxidative DNA damage and protein oxidation were significantly lower in the cells treated with NtBHA when the cells were exposed to ionizing radiation. The modulation of cellular redox status was more pronounced in control cells compared with NtBHA-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of ROS and the reduction of ATP production was significantly higher in control cells compared with NtBHA-treated cells. NtBHA administration before irradiation at 5 mg/kg daily for 2 weeks provided substantial protection against killing and oxidative damage to mice exposed to whole-body irradiation. These data indicate that NtBHA may have great application potential as a new class of in vivo, non-sulfur containing radiation protector.

Animals↗
PubMed1975

0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride as a sensitive derivatizing agent for the electron capture gas liquid chromatographic analysis of keto steroids.

0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride was used to prepare oximes of steroids with keto groups in selected positions; 3,17 and 20-monoketo; 3,17 and 3,20-diketo. Some of the 3-keto steroids had hindered 17-hydroxyl groups which were not readily amenable to esterification with perfluoroanhydrides, the most commonly used derivatizing agents for electron capture gas chromatographic analysis of hydroxy steroids. The oximes were readily prepared from 5 ng of each of the compounds tested, and with testosterone it was demonstrated that the derivative could be prepared from as little as 0.1 ng. The derivatives were stable to gas chromatography and extremely sensitive to electron capture detection. The sensitivity ranged from 1.5 X 10(4) coulombs per mole of progesterone. Because of the ease of preparation of the derivatives, their stability in common solvents and analytical manipulative techniques, the reagent would be suitable for the micro analysis of biologically significant keto steroids by electron capture gas chromatography.

Chromatography, Gas↗
PubMed1979

Formation of molecules of biological interest from formaldehyde and hydroxylamine in a modified sea medium.

As reported previously, glycine, serine, aspartic acid, and beta-alanine are the predominant amino acids produced from equimolecular formaldehyde and hydroxylamine in a modified sea medium enriched with essential transition metal ions. The time course of formation of the amino acids, and related substances was studied. Among the amino acids, glycine was produced earlier. Urea was produced initially and disappeared rapidly. Formation of cyanide, glycinenitrile, and glycinamide preceded the formation of amino acids. Probable pathways for the formation of amino acids and urea are suggested.

Amino Acids↗
PubMed1979

Highly purified hydroxylamine oxidoreductase derived from Nitrosomonas europaea. Some physicochemical and enzymatic properties.

Hydroxylamine oxidoreductase [EC 1.7.3.4] of Nitrosomonas europaea was purified to an electrophoretically homogeneous state and some of its properties were studied. The molecular weight of the enzyme as determined by gel filtration on Sephadex G150 and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate is 175,000-180,000, while the minimum molecular weight per heme determined from the dry weight and heme content is 17,500. The enzyme is a C-type cytochrome; its reduced form shows absorption peaks at 418 (gamma peak), 521 (beta peak), 553 (alpha peak), and 460 nm (due to an unidentified chromophore). Although the alpha peak at 553 nm has a shoulder at 559 nm, the enzyme does not posses protoheme or a cytochrome b subunit. It seems likely that the enzyme molecule possess heme c molecules in different states. The enzyme reacts rapidly with various eukaryotic cytochromes c, but does not react with "bacterial-type" cytochromes c. Although the enzyme does not react with cytochrome c-552 (N. europaea), another C-type cytochrome of the organism, cytochrome c-554 (N. europaea) acts as an electron acceptor for the enzyme.

Cyanides↗
PubMed2001

N-t-Butyl hydroxylamine is an antioxidant that reverses age-related changes in mitochondria in vivo and in vitro.

N-t-butyl hydroxylamine (NtBHA) delays senescence-dependent changes in human lung fibroblasts (IMR90) (Atamna et al., J. Biol. Chem. 275, 6741-6748). The current study examines the effect of NtBHA on mitochondria in old and young rats and human primary fibroblasts (IMR90). In NtBHA-treated rats, the age-dependent decline in food consumption and ambulatory activity was reversed without affecting body weight. The respiratory control ratio of mitochondria from liver of old rats improved after feeding NtBHA. These findings suggest that NtBHA improved mitochondrial function in vivo. The age-dependent increase in proteins with thiol-mixed disulfides was significantly lower in old rats treated with NtBHA. NtBHA was effective only in old rats; no significant effect was observed in young rats. In IMR90 cells, NtBHA delayed senescence-associated changes in mitochondria and cellular senescence induced by maintaining the cells under suboptimal levels of growth factors. Proteasomal activity was also higher in cells treated with NtBHA than in untreated cells. NtBHA accumulates in cells 10- to 15-fold the extracellular concentration and is maintained by mitochondrial NADH. NtBHA is an antioxidant that is recycled by mitochondrial electron transport chain and prevents radical-induced toxicity to mitochondria.

Aging↗
PubMedDate not supplied

Nitric oxide generation from hydroxylamine in the presence of neutrophils and in the cell-free system.

Conversion of hydroxylamine (HA) to nitric oxide (NO) has been studied in the presence or absence of human neutrophils with or without myristate acetate phorbol (PMA), catalase (CAT), hydrogen peroxide (H2O2), and superoxide dismutase (SOD) and nitric oxide synthase (NOS) inhibitors. The generation of NO from HA in the presence of neutrophils was higher than in the cell-free system. We found that catalase did not influence the nitrite generation from HA in the cell-free system and in the presence of neutrophils. The H2O2 enhanced the NO generation from HA in the presence of neutrophils only. When catalase and H2O2 were added together, a high increase of NO generation from HA in both systems was observed. The addition of SOD decreased whereas addition of PMA enhanced the NO generation from HA in the presence of neutrophils. The presented data show the possible role of oxygen radicals in the decomposition of HA to NO. The addition of NOS inhibitors to the culture of neutrophils decreased the generation of nitrite from HA. Our results suggest that NO generation from HA, which is an intermediate in NO production from L-arginine, may be supported by an enzymatic pathway in which cellular NO synthase is involved.

Catalase↗
PubMed1977

Oxidation of aliphatic hydroxylamines in aqueous solutions.

The effects of pH, buffer constituents, duration of storage, presence of air, heavy metal ions, extracting solvents and various additives and cofactors on the aerial oxidation of some aliphatic primary and secondary hydroxylamines were investigated. Copper ions were particularly effective catalysts of the oxidation reaction. Conditions to minimize this transformation are described.

Chelating Agents↗
PubMed1977

Derivatization to stabilize some aliphatic primary hydroxylamines for g.l.c. analysis.

By appropriate choice of trimethylsilylating and trifluoroacetylating reagents and organic solvents for extraction, stable derivative of aliphatic primary hydroxylamines metabolites, N-hydroxyphentermine, N-hydroxychlorphentermine, N-hydroxymexiletene, N-hydroxyphenethylamine, N-hydroxyamphetamine, and N-hydroxy-3,4-dimethoxyamphetamine, were obtained and examined by g.l.c. analysis without decomposition and without interference from the parent drug or other metabolic products.

Amines↗
PubMed2005

The effect of hydroxylamine on KATP channels in vascular smooth muscle and underlying mechanisms.

Hydroxylamine (HA) is a putative intermediate in the conversion of l-arginine to nitric oxide (NO). HA was reported to cause the relaxation of precontracted aorta strips; however, the ionic mechanisms of HA-induced vasorelaxation were not yet known. In the present study, the whole-cell patch-clamp technique was used to examine the effects of HA on ATP-sensitive K+ (K(ATP)) currents and membrane potentials in vascular smooth muscle cells from rat mesenteric arteries and underlying mechanisms. It was found that bath-applied HA reversibly enhanced K(ATP) currents in a concentration-dependent fashion with an EC50 of 54 +/- 3.4 microM and hyperpolarized the cell membrane from -48 +/- 5.2 to -65 +/- 7.5 mV (n = 6, p < 0.01). The increase in K(ATP) currents induced by HA was suppressed by superoxide dismutase (-380 +/- 45 to -160 +/- 20 pA, n = 4, p < 0.01) and N-acetyl-L-cysteine (-385 +/- 55 to -150 +/- 16 pA, n = 5, p < 0.01), indicating the involvement of different free radicals, including superoxide anion. Hypoxanthine/xanthine oxidase increased not only basal K(ATP) currents, but also HA-enhanced K(ATP) currents (from -355 +/- 40 to -480 +/- 62 pA, n = 6, p < 0.05). Sodium nitroprusside, a spontaneous NO donor, and a membrane-permeable cGMP analog (8-bromo-cGMP) were without effects on HA-enhanced K(ATP) currents or basal K(ATP) currents. Our results indicate that HA augmented K(ATP) channel activity and hyperpolarized cell membrane, possibly via increased free radical generation.

Adenosine Triphosphate↗
PubMed2001

Transcript analysis of multiple copies of amo (encoding ammonia monooxygenase) and hao (encoding hydroxylamine oxidoreductase) in Nitrosomonas europaea.

The genes encoding ammonia monooxygenase (amoCAB), hydroxylamine oxidoreductase (hao), and the c-type cytochrome c-554 (hcy) are present in multiple copies in the genome of Nitrosomonas europaea. The upstream regions of the two copies of amoC, the three copies of hao, and one copy of hcy were cloned and sequenced. Primer extension reactions were done to identify transcription start sites for these genes, as well as for amoA. Putative sigma(70) promoter sequences were found associated with all but one of the mapped transcription start sites. Primer extensions were done with amoC primers using RNA harvested from cells incubated with and without ammonium. The experiments suggested that N. europaea cells may be able to use different promoters in the presence and absence of ammonium.

Ammonia↗
PubMed1970

Streptomycin-induced phenotypic suppression of hydroxylamine-induced nonsense mutants in the rII A cistron of bacteriophage T4.

Twenty-one hydroxylamine-induced rII A cistron nonsense mutants were tested for streptomycin (SM)-induced phenotypic suppression by exposing Escherichia coli SBO (nonpermissive host) to phage in the presence and absence of SM. All nine amber, four of six ochre, and five of six opal mutants were phenotypically suppressible by SM. For suppressible mutants, the ratio of the average burst size in the presence of SM to size in the absence of SM ranged from 12 to 242 for the ambers, 3 to 33 for the ochres, and 4 to 14 for the opals. Increased susceptibility of the amber mutants to SM-induced phenotypic suppression relative to the susceptibility of the opal and ochre mutants may reflect a neighboring base effect, such that a 3'-terminal adenine inhibits misreading of a 5'-terminal uracil.

Coliphages↗
PubMed1971

Effect of inactivation by hydroxylamine on early functions of poliovirus.

Evidence is presented that poliovirus particles with a single lethal hit by hydroxylamine do not induce in host cells either inhibition of cellular protein synthesis or viral ribonucleic acid (RNA) replication. The RNA of these viruses is not replicated even if the cells are simultaneously infected with both active and inactivated viruses. The damaged viral RNA seems to have lost both its template function and its function in the translation of normal viral proteins.

Amino Acids↗
PubMed1992

Histamine potentiation by hydroxylamines: structure-activity relations; inhibition of diamine oxidase.

Hydroxylamines potentiated the responses of the canine colonic epithelium to histamine but not to other agonists such as serotonin or carbachol. We tested the hypothesis that an inhibition of histamine catabolism could explain the observed potentiation. A clear structure activity relation was defined, active compounds having the structure NH2-O-R, R being a simple uncharged aliphatic group. Active compounds delayed the disappearance of histamine from the bathing solutions and inhibited colonic diamine oxidase, an effect mimicked by standard inhibitors aminoguanidine and semicarbazide. Histamine agonists that possessed an imidazole nucleus (2- and 4-methylhistamine) were affected, whereas impromidine, 2 pyridylethylamine, and dimaprit were not. Agonist specificity combined with the enzyme data suggest an inhibition of histamine catabolism as a possible mechanism for the potentiating effects observed.

Amine Oxidase (Copper-Containing)↗