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PubMed1979

Characterization of cyanide-insensitive respiration in mitochondria and submitochondrial particles of Moniliella tomentosa.

Mitochondria and submitochondrial particles of the osmophilic yeast-like fungus Moniliella tomentosa may respire by means of two pathways: a normal cytochrome pathway, sensitive to cyanide and antimycin A, and an alternative pathway, which is insensitive to these inhibitors but is specifically inhibited by salicylhydroxamic acid. The affinities of both oxidases for succinate and NADH as substrates, for O(2) as terminal electron acceptor, and for AMP as stimulator of the alternative oxidase were determined. 1. Submitochondrial particles of M. tomentosa may also respire by means of a cyanide-sensitive and/or cyanide-insensitive system. 2. The activities of both oxidases as compared with the total activity are roughly the same in submitochondrial particles as in the original mitochondria. 3. The terminal oxidase of the cyanide-insensitive pathway requires a 10-fold higher O(2) concentration for saturation than does cytochrome c oxidase. 4. The apparent K(m) for succinate is about 3 times higher for the alternative than for the normal oxidase when measured in mitochondria, and 4-10 times higher when measured in submitochondrial particles. The apparent K(m) for NADH is roughly the same for both oxidases. 5. The apparent K(m) values of both oxidases for succinate are always lower in submitochondrial particles than in mitochondria. 6. The apparent K(m) for AMP, acting as a stimulator of the alternative oxidase, is the same (25mum) in mitochondria as in sub-mitochondrial particles. These results are discussed in the light of the structure and localization of the components of the alternative oxidase.

Adenosine Monophosphate↗

PubMed2002

Pseudomonas aeruginosa RoxR, a response regulator related to Rhodobacter sphaeroides PrrA, activates expression of the cyanide-insensitive terminal oxidase.

The facultative anaerobe Pseudomonas aeruginosa has multiple aerobic electron transport pathways, one of which is terminated by a cyanide-insensitive oxidase (CIO). This study characterizes a P. aeruginosa two-component system that regulates CIO production. The response regulator of this system (RoxR) has significant amino acid sequence similarity to PrrA of Rhodobacter sphaeroides and related proteins in other alpha-proteobacteria. In heterologous complementation analysis, R. sphaeroides PrrA rescued the growth defect of a P. aeruginosa mutant lacking RoxR, and RoxR enabled photosynthetic growth of an R. sphaeroides PrrA mutant. Also, RoxR could substitute for PrrA in activating transcription in vitro, demonstrating that these proteins are functional homologues. P. aeruginosa strains lacking RoxR or the sensor kinase (RoxS) were more sensitive than wild type to the respiratory inhibitors cyanide and azide. The phenotypes of these mutant strains correlated with reduced cyanide-insensitive O2 utilization and less cyanide-dependent expression of the locus encoding the CIO (cioAB). The ability of purified RoxR to bind to the cioAB promoter region also suggests that this protein acts directly to regulate cioAB transcription. Therefore, RoxR appears to play a role in regulating the transcription of loci for P. aeruginosa energy-generating enzymes similar to that of its homologues in alpha-proteobacteria.

Bacterial Proteins↗

PubMed2000

Biodetoxification of silver-cyanide from electroplating industry wastewater.

A bacterial consortium capable of utilizing metal-cyanides as a source of nitrogen was used to develop a microbiological process for the detoxification of silver-cyanide from electroplating wastewater. When the treatment was carried out in a 27-l rotating biological contactor (R3C) in continuous mode, the system could achieve > 99.5% removal of 0.1 mmol l(-1) silver-cyanide (approximately 5 mg l(-1) cyanide and 10 mg l(-1) silver) in 10 h with sugarcane molasses (0.1 ml l(-1)) as carbon source. The silver ions set free during biodegradation were efficiently adsorbed by the bacterial biomass. The RBC-treated effluent was found to be safe for discharge into the environment, as confirmed by chemical analysis and fish bioassay studies.

Animals↗

PubMed1996

Infrared and EPR studies on cyanide binding to the heme-copper binuclear center of cytochrome bo-type ubiquinol oxidase from Escherichia coli. Release of a CuB-cyano complex in the partially reduced state.

Cyanide-binding to the heme-copper binuclear center of bo-type ubiquinol oxidase from Escherichia coli was investigated with Fourier transform-infrared and EPR spectroscopies. Upon treatment of the air-oxidized CN-inhibited enzyme with excess sodium dithionite, a 12C-14N stretching vibration at 2146 cm-1 characteristic of the FeO3+ C=N CuB2+ bridging structure was quickly replaced with another stretching mode at 2034.5 cm-1 derived from the FeO2+ C=N moiety. The presence of ubiquinone-8 or ubiquinone-1 caused a gradual autoreduction of the metal center(s) of the air-oxidized CN-inhibited enzyme and a concomitant appearance of a strong cyanide stretching band at 2169 cm-1. This 2169 cm-1 species could not be retained with a membrane filter (molecular weight cutoff = 10,000) and showed unusual cyanide isotope shifts and a D2O shift. These observations together with metal content analyses indicate that the 2169 cm-1 band is due to a CuB.CN complex released from the enzyme. The same species could be produced by anaerobic partial reduction of the CN-inhibited ubiquinol oxidase and, furthermore, of the CN-inhibited cytochrome c oxidase; but not at all from the fully reduced CN-inhibited enzymes. These findings suggest that there is a common intermediate structure at the binuclear center of heme-copper respiratory enzymes in the partially reduced state from which the CuB center can be easily released upon cyanide-binding.

Anaerobiosis↗

PubMed2004

The auxiliary protein HypX provides oxygen tolerance to the soluble [NiFe]-hydrogenase of ralstonia eutropha H16 by way of a cyanide ligand to nickel.

The hypX gene of the facultative lithoautotrophic bacterium Ralstonia eutropha is part of a cassette of accessory genes (the hyp cluster) required for the proper assembly of the active site of the [NiFe]-hydrogenases in the bacterium. A deletion of the hypX gene led to a severe growth retardation under lithoautotrophic conditions with 5 or 15% oxygen, when the growth was dependent on the activity of the soluble NAD+ -reducing hydrogenase. The enzymatic and infrared spectral properties of the soluble hydrogenase purified from a HypX-negative strain were compared with those from an enzyme purified from a HypX-positive strain. In activity assays under anaerobic conditions both enzyme preparations behaved the same. Under aerobic conditions, however, the mutant enzyme became irreversibly inactivated during H2 oxidation with NAD+ or benzyl viologen as the electron acceptor. Infrared spectra and chemical determination of cyanide showed that one of the four cyanide groups in the wild-type enzyme was missing in the mutant enzyme. The data are consistent with the proposal that the HypX protein is specifically involved in the biosynthetic pathway that delivers the nickel-bound cyanide. The data support the proposal that this cyanide is crucial for the enzyme to function under aerobic conditions.

Bacterial Proteins↗

PubMed1993

The effects of chronic cassava consumption, cyanide intoxication and protein malnutrition on glucose tolerance in growing rats.

Intraperitoneal glucose tolerance tests were performed at 4-week intervals in groups of weanling rats before and after feeding with maize- or cassava-based diets with and without adequate protein and sublethal cyanide supplementation. Weaning weights were doubled (increase of about 50 g) after 4 weeks on control (maize-based with adequate protein) and protein-replete diets. Weight gain on the protein-deficient diets was much less (22 g or 50%), a pattern maintained by the rats on these diets until the age of 12 weeks. Plasma thiocyanate levels were identical at weaning and after 8 weeks of the control diet but increased by 200-300% after 4 weeks intake of the cassava or cyanide-supplemented feeds. Levels returned to normal in all groups after a further 4 weeks feeding with the control diet. Glucose tolerance (as assessed by the area under the 2 h glucose v. time curve) was impaired to a varying extent in the rats after 4 weeks on the various diets: protein-replete cassava and protein-deficient maize diets by 50% protein-deficient cassava diet by 300%, and cyanide-supplemented protein-deficient maize diet by 150%. The derangement in the rats on the protein-replete cassava diet was unaffected by a further 4 weeks intake of the control diet, unlike in the other groups where there was significant improvement in the glucose tolerance indices at the same time. It is concluded that in growing rats: (1) cassava intake and protein malnutrition may have independent and additive effects on the genesis of glucose intolerance, (2) cyanide supplementation of a cassava-free protein-replete diet has no effect on glucose tolerance.

Animals↗

PubMed2001

Ecological variation of intake of cassava food and dietary cyanide load in Nigerian communities.

AIM: To study the ecological variation of intake of cassava foods and dietary cyanide load. DESIGN: Ecological study design. SETTING: Five communities in south-western Nigeria where tropical ataxic neuropathy (TAN) was described as endemic (area A), 11 communities in south-western Nigeria where TAN was described as absent (area B), and five communities in northern Nigeria (area C). SUBJECTS: Subjects were randomly sampled from selected communities. Intake of cassava foods was estimated from dietary history and dietary cyanide load was estimated from urine thiocyanate concentrations. Residual cyanogens in cassava food samples from the community markets were determined. RESULTS: In total, 1272 subjects from 21 communities - 238 from area A, 659 from area B and 375 from area C - were selected. Intake of cassava food per person per week was 17 meals in area A, 10 meals in area B, and one meal in area C. Geometrical mean urine thiocyanate concentrations were 73 micromol l(-1), 51 micromol l(-1) and 17 micromol l(-1) in areas A, B and C, respectively. Mean residual cyanogen content in cassava food samples was 16 mg HCN eq kg(-1) (confidence interval (CI) 13-18) in area A, and 13 mg HCN eq kg(-1) in area B (CI 11-14). CONCLUSION: This study shows that the intake of cassava foods and dietary cyanide load is high in several communities in south-western Nigeria, predominantly in communities where TAN has been reported. Dietary cyanide load in these communities appears to be determined by the combination of frequency of intake and cyanogen content of cassava foods. Measures to improve the effectiveness of removal of cyanogen from cassava roots during processing are needed in the affected communities.

Child↗

PubMed1985

In vivo and in vitro release of cyanide from neurotoxic aminonitriles.

Cyanide release from neurotoxic aminonitriles was measured following in vitro incubation with both microsomes and liver slices. Investigation of cyanide released as urinary thiocyanate following ip aminonitrile administration to rats was also measured. The yield of cyanide in the in vivo study, as measured by the mole percent of administered dose, was greatest from dimethylaminonitrile (DMAA), followed by trimethylaminopropionitrile (TMAPN), dimethylaminopropionitrile (DMAPN), 3,3'-iminodipropionitrile (IDPN), dimethylaminobutyronitrile (DMABN), and monomethylaminopropionitrile (MMAPN). Urinary excretion of thiocyanate accounted for 48.9% of the administered DMAA, 11.6% of TMAPN, 8.0% of DMAPN, 6.8% of IDPN, 3.1% of DMABN, and 1.8% of MMAPN. Incubation of aminonitriles and related compounds with microsomes or liver slices from rats yielded measurable quantities of cyanide from all the compounds tested except for DMABN, TMABN, and succiononitrile. Quantitative evaluation of the yield of formaldehyde by demethylation following microsomal incubation was also determined. The signs of acute toxicity in rats after ip administration of KCN were similar only to those in rats administered DMAA.

Aminopropionitrile↗

PubMed2006

Efficacy of hydroxocobalamin for the treatment of acute cyanide poisoning in adult beagle dogs.

INTRODUCTION: The efficacy of hydroxocobalamin for acute cyanide poisoning was compared with that of saline vehicle in dogs. METHODS: Anesthetized adult beagle dogs were administered potassium cyanide (0.4 mg/kg/min, IV) until 3 min after the onset of apnea. Hydroxocobalamin (75 mg/kg [n = 19] or 150 mg/kg [n = 18], IV) or saline vehicle [n = 17] was then infused over 7.5 min while animals were ventilated with 100% oxygen, which was stopped after 15 min. RESULTS: In vehicle-treated animals cyanide produced deterioration that culminated in a moribund state requiring euthanasia within 4 h in 10 of 17 animals and in neurological deficits necessitating euthanasia within 2-4 d in an additional 4 animals (mortality rate 82%). Survival through 14 d was observed in 15 of 19 animals administered hydroxocobalamin 75 mg/kg (mortality rate 21%), and 18 of 18 administered hydroxocobalamin 150 mg/kg (mortality rate 0%). CONCLUSION: Hydroxocobalamin reversed cyanide toxicity and reduced mortality in a canine model.

Acute Disease↗

PubMed2004

Oxidative treatment of cyanide in wastewater using hydrogen peroxide and homogeneous catalyst.

Batch kinetic tests were conducted to determine the effects of experimental conditions and catalysts on cyanide degradation. Cyanide degradation by hydrogen peroxide was found to follow first-order kinetics. Reaction rates increased with increasing pH and decreasing temperature. The activation energy for cyanide degradation by hydrogen peroxide was found to be -13.81 kJ/mol. The addition of Cu2+ or Cd2+ as catalysts resulted in increasing reaction rates. In alkaline conditions, the catalytic effects of Cu2+ or Cd2+ were accelerated and Cu2+ was found to be a more effective catalyst than Cd2+. The practical relevance of the laboratory oxidation method of cyanide was demonstrated for actual industrial wastewater.

Catalysis↗

PubMedDate not supplied

A rapid, sensitive, and specific screening technique for the determination of cyanide.

A colorimetric method for the screening of cyanide in biological specimens is presented. Cyanide in a 200-microL sample is diffused in a Conway 3 compartment dish into the center well where it catalyzes the reaction between p-nitrobenzaldehyde and o-dinitrobenzene. The resulting blue-violet color intensity is proportional to cyanide concentration. The reaction is specific for cyanide, and concentrations as low as 0.05 mg/L can readily be detected.

Body Fluids↗

PubMedDate not supplied

Multicomponent spectroscopic assay for hemoglobin and ferrihemoglobin species in methemoglobin treatment of cyanide poisoning.

Monitoring the concentrations of various hemoglobin and ferrihemoglobin species and their cyanide complexes is important in the study of the efficacy of methemoglobin-forming agents for the treatment of cyanide toxicity. In this study, the visible absorption spectra of three hemoglobin intermediates were experimentally determined and compared with computer-generated spectra. The data supported the assumption that the molar absorptivities of the intermediates are equivalent to the combined absorptivities of the component subunits. A multicomponent Fourier transform (FT)-aided full spectrum quantitation system (FSQ) to simultaneously measure hemoglobin (Hb), hemimethemoglobin (hemiMetHb), and the cyanide complex dicyanohemimethemoglobin (dicyhemiMetHb) was also evaluated. It was found that FSQ had satisfactory accuracy and precision to quantitate hemiMetHb and dicyhemiMetHb at concentrations from 2 to 20% of the total Hb, a range commonly encountered in the treatment of cyanide poisoning using methemoglobin-forming agents. The simplicity and rapid throughput of the method make it suitable for clinical evaluation studies and form the basis for the design of a portable instrument for field analysis of these species.

Calibration↗

PubMedDate not supplied

A new spectrophotometric method for the toxicological diagnosis of cyanide poisoning.

A spectrophotometric method for the determination of hydrogen cyanide in biological fluids based on the release of cyanide ion by the addition of a strong acid and its subsequent specific reaction with hydroxocobalamin to give cyanocobalamin is proposed. The release of cyanide ion is accelerated by aeration with a stream of an inert gas (nitrogen) that carries it into the hydroxocobalamin solution. Although the in vitro reaction develops to completion within 20 min, reproducible quantitation in biological media takes 45 min. The cyanocobalamin formed is quantitated by second-derivative visible spectrophotometry from the absorbance difference between 333 and 361 nm, the measured signal being proportional to the cyanide ion concentration in the sample.

Forensic Medicine↗

PubMed1989

Possible role of a 36 kDa protein induced by respiratory inhibitors in cyanide-resistant respiration in Hansenula anomala.

The antimycin A or cyanide-dependent appearance of a 36 kDa protein in the particulate fraction was observed in L-[35S]methionine pulse-labeling experiments on cells of Hansenula anomala, in which cyanide-resistant respiration was induced. The combined addition of cycloheximide or anaerobiosis, which block the induction of cyanide-resistant respiration, repressed the synthesis of this protein. These results suggest the involvement of the particulate 36 kDa protein in cyanide-resistant respiration.

Antimetabolites↗

PubMed1975

Formate dehydrogenase. Subunit and mechanism of inhibition by cyanide and azide.

Formate dehydrogenase (EC 1.2.1.2) prepared from peas (Pisum sativum) was a two-subunit enzyme. The enzyme accelerated the formation of an NAD+-cyanide compound having an adsorption band at 330 nm. The enzyme was able to bind one NAD+ molecule per each subunit but only 1 mole of NAD+-cyanide compound was formed per two subunits. The complex of NAD+, cyanide, and the enzyme was very stable and had no catalytic activity. Azide inhibited the formate dehydrogenase reaction in two different ways. By incubation of the enzyme with azide in the presence of NAD+, half of its catalytic activity was lost. The remaining activity was also inhibited by azide but this inhibition was removed competively by formate. Contrary to the case of cyanide the inhibition by azide could be removed by dialysis and no spectral species due to the addition compound of NAD+ and azide could be observed. The data from double recipricol plots of the initial velocity and the formate concentration led to a conclusion that formate dehydrogenase has two sites with about equal catalytic activity. The Km for formate was different for the two catalytic sites (1.67 and 6.25 mM) but the difference was not noticeable in the case of the Km for NAD+.

Aldehyde Oxidoreductases↗

PubMed2002

Linamarase expression in cassava cultivars with roots of low- and high-cyanide content.

This paper reports the expression and localization of linamarase in roots of two cassava (Manihot esculenta Crantz) cultivars of low and high cyanide. Two different patterns of linamarase activity were observed. In the low-cyanide type, young leaves displayed very high enzyme activity during the early plant growing stage (3 months), whereas in root peel, the activity increased progressively to reach a peak in 11-month-old plants. Conversely, in the high-cyanide cultivar (HCV), root peel linamarase activity decreased during the growth cycle, whereas in expanded leaves linamarase activity peaked in 11-month-old plants. The accumulation of linamarin showed a similar pattern in both cultivars, although a higher concentration was always found in the HCV. Linamarase was found mainly in laticifer cells of petioles and roots of both cultivars with no significant differences between them. At the subcellular level, there were sharp differences because linamarase was found mainly in the cell walls of the HCV, whereas in the low-cyanide cultivar, the enzyme was present in vacuoles and cell wall of laticifer cells. Reverse transcriptase-PCR on cassava tissues showed no expression of linamarase in cassava roots, thus, the transport of linamarase from shoots to roots through laticifers is proposed.

Biological Transport↗

PubMed1984

The appearance and characterization of cyanide-resistant respiration in the fungus Candida albicans.

The respiration of yeast-form cells of the dimorphic fungus Candida albicans became resistant to cyanide during aging treatment in the resting state. An alternative, cyanide-resistant respiratory pathway was found to develop fully in cells aged at a concentration of 0.75 X 10(9)/ml or more at 25 C, but did not appear at 5 C. Chloramphenicol did not prevent the appearance of the alternative respiratory pathway. The effects of inhibitors, salicylhydroxamic acid (SHAM) and disulfiram (tetraethylthiuram disulfide), on respiration of aged cells were examined, and results indicated that SHAM binds at a site on the alternative respiratory pathway whereas disulfiram binds at two sites, one on the conventional respiratory pathway and the other on the alternative pathway. Thus, SHAM is a more selective inhibitor of the alternative respiration of C. albicans cells. SHAM-titration of the alternative respiration revealed that less than 10% of the maximal activity of the alternative respiratory pathway was utilized under normal conditions, indicating that the alternative respiratory pathway makes a small contribution to the total respiration. It was therefore concluded that the alternative, cyanide-resistant respiratory pathway operates fully when the cyanide-sensitive, cytochrome pathway is blocked although aged cells possess both respiratory pathways.

Binding Sites↗

PubMed1977

Chronic administration of cyanide: urinary excretion of thiocyanate in male and female rats.

The urinary elimination of thiocyanate was investigated in male and female rats following the chronic administration of potassium cyanide. Female rats dosed at the level of 5 mg KCN/kg once a week and twice a week respectively, displayed no significant difference in the excretion of thiocyanate in urine after periods of up to eight weeks of study. Similarly, male rats that were administered 5 mg/KCN/kg twice weekly showed no significant difference in the amount of thiocyanate excreted. The elimination patterns of thiocyanate in male and female rats showed no significant differences. The results suggest that a substrate saturation phenomenon is not operative with cyanide metabolism at the dosage level of potassium cyanide employed in this study. This is contrary to a previously published study which reported that the urinary excretion of thiocyanate decreased after chronic potassium cyanide administration.

Animals↗