Cyanide Detoxification Research Articles

Dietary resources shape the adaptive changes of cyanide detoxification function in giant panda (Ailuropoda melanoleuca).

The functional adaptive changes in cyanide detoxification in giant panda appear to be response to dietary transition from typical carnivore to herbivorous bear. We tested the absorption of cyanide contained in bamboo/bamboo shoots with a feeding trial in 20 adult giant pandas. We determined total cyanide content in bamboo shoots and giant panda’s feces, levels of urinary thiocyanate and tissue rhodanese activity using color reactions with a spectrophotometer. Rhodanese expression in liver and kidney at transcription and translation levels were measured using real-time RT-PCR and immunohistochemistry, respectively. We compared differences of rhodanese activity and gene expressions among giant panda, rabbit (herbivore) and cat (carnivore), and between newborn and adult giant pandas. Bamboo shoots contained 3.2 mg/kg of cyanide and giant pandas absorbed more than 65% of cyanide. However, approximately 80% of absorbed cyanide was metabolized to less toxic thiocyanate that was discharged in urine. Rhodanese expression and activity in liver and kidney of giant panda were significantly higher than in cat, but lower than in rabbit (all P < 0.05). Levels in adult pandas were higher than that in newborn cub. Phylogenetic analysis of both nucleotide and amino acid sequences of the rhodanese gene supported a closer relationship of giant panda with carnivores than with herbivores.

The β-cyanoalanine synthase pathway: beyond cyanide detoxification.

Production of cyanide through biological and environmental processes requires the detoxification of this metabolic poison. In the 1960s, discovery of the β-cyanoalanine synthase (β-CAS) pathway in cyanogenic plants provided the first insight on cyanide detoxification in nature. Fifty years of investigations firmly established the protective role of the β-CAS pathway in cyanogenic plants and its role in the removal of cyanide produced from ethylene synthesis in plants, but also revealed the importance of this pathway for plant growth and development and the integration of nitrogen and sulfur metabolism. This review describes the β-CAS pathway, its distribution across and within higher plants, and the diverse biological functions of the pathway in cyanide assimilation, plant growth and development, stress tolerance, regulation of cyanide and sulfide signalling, and nitrogen and sulfur metabolism. The collective roles of the β-CAS pathway highlight its potential evolutionary and ecological importance in plants.

Development of sulfanegen for mass cyanide casualties.

Cyanide is a metabolic poison that inhibits the utilization of oxygen to form ATP. The consequences of acute cyanide exposure are severe; exposure results in loss of consciousness, cardiac and respiratory failure, hypoxic brain injury, and dose-dependent death within minutes to hours. In a mass-casualty scenario, such as an industrial accident or terrorist attack, currently available cyanide antidotes would leave many victims untreated in the short time available for successful administration of a medical countermeasure. This restricted therapeutic window reflects the rate-limiting step of intravenous administration, which requires both time and trained medical personnel. Therefore, there is a need for rapidly acting antidotes that can be quickly administered to large numbers of people. To meet this need, our laboratory is developing sulfanegen, a potential antidote for cyanide poisoning with a novel mechanism based on 3-mercaptopyruvate sulfurtransferase (3-MST) for the detoxification of cyanide. Additionally, sulfanegen can be rapidly administered by intramuscular injection and has shown efficacy in many species of animal models. This article summarizes the journey from concept to clinical leads for this promising cyanide antidote.

Lower sulfurtransferase detoxification rates of cyanide in konzo—A tropical spastic paralysis linked to cassava cyanogenic poisoning

Using a matched case-control design, we sought to determine whether the odds of konzo, a distinct spastic paraparesis associated with food (cassava) cyanogenic exposure in the tropics, were associated with lower cyanide detoxification rates (CDR) and malnutrition. Children with konzo (N=122, 5–17 years of age) were age- and sex-matched with presumably healthy controls (N=87) and assessed for motor and cognition performances, cyanogenic exposure, nutritional status, and cyanide detoxification rates (CDR). Cyanogenic exposure was ascertained by thiocyanate (SCN) concentrations in plasma (P-SCN) and urine (U-SCN). Children with a height-for-age z-score (HAZNCHS)<-2 were classified as nutritionally stunted. CDR was measured as time required to convert cyanide to SCN, and expressed as ms/μmol SCN/mg protein or as mmolSCN/ml plasma/min. Mean (SD) U-SCN in children with konzo was 521.9 (353.6) μmol/l and was, significantly higher than 384.6 (223.7) μmol/l in those without konzo. Conditional regression analysis of data for age- and sex- matched case-control pairs showed that konzo was associated with stunting (OR: 5.8; 95% CI: 2.7–12.8; p<0.01; N=83 paired groups) and higher U-SCN (OR: 1.1; 95% CI: 1.02–1.20 per 50-μmol increase in U-SCN; p=0.02; N=47 paired groups). After adjusting for stunting and U-SCN, the odds of developing konzo was reduced by 63% (95% CI: 11–85%, p=0.03; N=41 paired groups) for each 5mmol SCN/(ml plasma/min)-increase in CDR. Linear regression analysis indicated a significant association between BOT-2 or KABC-II scores and both the HAZNCHS z-score and the U-SCN concentration, but not the CDR. Our findings provide evidence in support of interventions to remove cyanogenic compounds from cassava prior to human consumption or, peharps, enhance the detoxification of cyanide in those relying on the cassava as the main source of food.

Determination of the Michaelis-Menten kinetics and the genes expression involved in phyto-degradation of cyanide and ferri-cyanide.

Hydroponic experiments were conducted with different species of plants (rice, maize, soybean and willow) exposed to ferri-cyanide to investigate the half-saturation constant (K M ) and the maximal metabolic capacity (v max ) involved in phyto-assimilation. Three varieties for each testing species were collected from different origins. Measured concentrations show that the uptake rates responded biphasically to ferri-cyanide treatments by showing increases linearly at low and almost constant at high concentrations from all treatments, indicating that phyto-assimilation of ferri-cyanide followed the Michaelis-Menten kinetics. Using non-linear regression, the highest v max was by rice, followed by willows. The lowest v max was found for soybean. All plants, except maize (DY26) and rice (XJ12), had a similar K M value, suggesting the same enzyme was active in phyto-assimilation of ferri-cyanide. Transcript level, by real-time quantitative PCR, of enzymes involved in degradation of cyanides showed that the analyzed genes were differently expressed during different cyanides exposure. The expression of CAS and ST genes responded positively to KCN exposure, suggesting that β-CAS and ST pathways were two possible pathways for cyanide detoxification in rice. The transcript level of NIT and ASPNASE genes also showed a remarkable up-regulation to KCN, implying the contribution to the pool of amino acid aspartate, which is an end product of CN metabolism. Up-regulation of GS genes suggests that acquisition of ammonium released from cyanide degradation may be an additional nitrogen source for plant nutrition. Results also revealed that the expressions of these genes, except for GS, were relatively constant during iron cyanide exposure, suggesting that they are likely metabolized by plants through a non-defined pathway rather than the β-CAS pathway.

Microbial transcriptome profiling of black band disease in a Faviid coral during a seasonal disease peak.

The etiology of black band disease (BBD), a persistent, globally distributed coral disease characterized by a dark microbial mat, is still unclear. A metatranscriptomics approach was used to unravel the roles of the major mat constituents in the disease process. By comparing the transcriptomes of the mat constituents with those of the surface microbiota of diseased and healthy corals, we showed a shift in bacterial composition and function in BBD-affected corals. mRNA reads of Cyanobacteria, Bacteroidetes and Firmicutes phyla were prominent in the BBD mat. Cyanobacterial adenosylhomocysteinase, involved in cyanotoxin production, was the most transcribed gene in the band consortium. Pathogenic and non-pathogenic forms of Vibrio spp., mainly transcribing the thiamine ABC transporter, were abundant and highly active in both the band and surface tissues. Desulfovibrio desulfuricans was the primary producer of sulfide in the band. Members of the Bacilli class expressed high levels of rhodanese, an enzyme responsible for cyanide and sulfide detoxification. These results offer a first look at the varied functions of the microbiota in the disease mat and surrounding coral surface and enabled us to develop an improved functional model for this disease.

Cyanide detoxification in an insect herbivore: Molecular identification of β-cyanoalanine synthases from Pieris rapae

Cyanogenic compounds occur widely in the plant kingdom. Therefore, many herbivores are adapted to the presence of these compounds in their diet by either avoiding cyanide release or by efficient cyanide detoxification mechanisms. The mechanisms of adaptation are not fully understood. Larvae of Pieris rapae (Lepidoptera: Pieridae) are specialist herbivores on glucosinolate-containing plants. They are exposed to cyanide during metabolism of phenylacetonitrile, a product of benzylglucosinolate breakdown catalyzed by plant myrosinases and larval nitrile-specifier protein (NSP) in the gut. Cyanide is metabolized to β-cyanoalanine and thiocyanate in the larvae. Here, we demonstrate that larvae of P. rapae possess β-cyanoalanine activity in their gut. We have identified three gut-expressed cDNAs designated PrBSAS1-PrBSAS3 which encode proteins with similarity to β-substituted alanine synthases (BSAS). Characterization of recombinant PrBSAS1-PrBSAS3 shows that they possess β-cyanoalanine activity. In phylogenetic trees, PrBSAS1-PrBSAS3, the first characterized insect BSAS, group together with a characterized mite β-cyanoalanine synthase and bacterial enzymes indicating a similar evolutionary history.

ChemInform Abstract: Recent Trends in the Development of Vitamin B12 Derivatives for Medicinal Applications

AbstractReview: 192 refs.

MAKANAN MENTAH, GOITROGENIK DAN GANGGUAN AKIBAT KEKURANGAN YODIUM (GAKY) (Raw Food, Goitrogenic and IDD)

Background: Raw foodism, consumed no processed food is becoming a lifestyle choice in the community, but it should be noted that the availability of nutrients goitrogenic on some commonly vegetables consumed by the people. Thiocyanate, cyanide detoxification substance goitrogenic results with working mechanisms disrupt thyroid function by inhibiting iodine intake and thyroid peroxidase activity interferes with a risk factor Iodine deficiency disorder (IDD). Methods: Samples in the form of common vegetables consumed in endemic goiter area in Jember Region. Cyanide content analysis with spectofotometri method performed on the greens with some food processing. Results:Cyanide content on vegetables from Jember Region was around 0,01–0,40 ppm, the highest was in cassava and the lowest in cabbage and “gambas”. After some processing methods practiced by society, cyanide levels in food stuffs become 0,18-0,0001 ppm. Conclusion:Blanching is the best way to reduce cyanide than the usual way. Recommendation:the adherents of raw food is expected to be more selective in choosing the type of vegetables to be consumed so that the purpose of the requirement for the body of nutrients and enzymes does not bring the other nutritional problems such as IDD.

Evaluation of the activity of cyanide-metabolizing sulfurtransferase enzymes in different tissues of turkey (Meleagris gallopavo).

This study was undertaken to estimate specific activities of rhodanese and 3-mercaptopyruvate sulfurtransferase (MST) in different tissues of turkey. Enzyme activities were determined in tissue samples from freshly killed adult male turkeys by measurement of thiocyanate amounts produced by the action of enzymes on suitable substrates. Activities of rhodanese and MST in examined tissues of turkey range from 0.023 to 0.448 and 0.01 to 0.191, respectively. The highest activity of the rhodanese was observed in the liver followed by the kidney and then heart, with statistically significant difference between them. Indeed, the activities of MST were significantly higher in hepatic and renal tissues of turkey than in other examined tissues. Although both sulfurtransferases were detected in brain and all studied parts of the digestive tract, the mean values of enzyme activities were far less compared with those of liver and kidney. The results suggest high potential of liver and kidney in sulfurtransferases mediated cyanide detoxification in turkey. However, the demonstration of both enzyme activities in all examined tissues supports the involvement of them in other biochemical processes besides cyanide detoxification which needs to be clarified in detailed studies.

Comparison of sulfur transferases in various tissue and mitochondria of rats with type 1 diabetes mellitus induced by streptozotocin

This study aims to investigate the relationship between sulfurtransferase (STS) activities [rhodanese (TST), mercaptopyruvate sulfurtransferase (MST)] involved in the catalysis of several biochemical reactions including detoxification of cyanide (CN−), restructuring of Fe-S cluster in proteins, and detoxification of oxygen radicals. Rats with type 1 diabetes mellitus induced by streptozotocin (STZ) were anesthetized at 14th day, and liver, lung, kidney, and heart tissues were extracted. All samples were homogenized, and mitochondrial parts were separated. Same processes were performed also in the control group, and TST and MST activities were measured in each part. The homogenate MST (MST Homo .) activities of the type 1 diabetes mellitus group were compared with the control group, and a decrease was observed in the lung, liver, and kidney, respectively; at the same time, an increase was seen in the heart tissue. The mitochondrial MST (MST Mito .) activities of rats with type 1 diabetes mellitus group were compared with the control group, and a decrease was found in all tissues. The highest decrease in the TST Mito . level of rats with type 1 diabetes mellitus was observed in kidney tissue. The TST activities of the type 1 diabetes mellitus group were compared with the control group, and a decrease was observed in the liver, lung, and kidney, respectively; at the same time, an increase was seen in the heart tissue. It is demonstrated in the present study that decreases occur both in enzyme levels of tissue homogenates and in mitochondria, of rats with induced type 1 diabetes mellitus. However, these results were not statistically significant. In the presence of these findings, we think that kidney, liver, lung, and heart tissue can be affected by type 1 diabetes in the long term.

Possible roles of plant sulfurtransferases in detoxification of cyanide, reactive oxygen species, selected heavy metals and arsenate.

Plants and animals have evolved various potential mechanisms to surmount the adverse effects of heavy metal toxicity. Plants possess low molecular weight compounds containing sulfhydryl groups (-SH) that actively react with toxic metals. For instance, glutathione (γ-Glu-Cys-Gly) is a sulfur-containing tripeptide thiol and a substrate of cysteine-rich phytochelatins (γ-Glu-Cys)2–11-Gly (PCs). Phytochelatins react with heavy metal ions by glutathione S-transferase in the cytosol and afterwards they are sequestered into the vacuole for degradation. Furthermore, heavy metals induce reactive oxygen species (ROS), which directly or indirectly influence metabolic processes. Reduced glutathione (GSH) attributes as an antioxidant and participates to control ROS during stress. Maintenance of the GSH/GSSG ratio is important for cellular redox balance, which is crucial for the survival of the plants. In this context, sulfurtransferases (Str), also called rhodaneses, comprise a group of enzymes widely distributed in all phyla, paving the way for the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors, at least in vitro. The best characterized in vitro reaction is the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate. Plants as well as other organisms have multi-protein families (MPF) of Str. Despite the presence of Str activities in many living organisms, their physiological role has not been clarified unambiguously. In mammals, these proteins are involved in the elimination of cyanide released from cyanogenic compounds. However, their ubiquity suggests additional physiological functions. Furthermore, it is speculated that a member of the Str family acts as arsenate reductase (AR) and is involved in arsenate detoxification. In summary, the role of Str in detoxification processes is still not well understood but seems to be a major function in the organism.

Sulfide detoxification in plant mitochondria.

In contrast to animals, which release the signal molecule sulfide in small amounts from cysteine and its derivates, phototrophic eukaryotes generate sulfide as an essential intermediate of the sulfur assimilation pathway. Additionally, iron-sulfur cluster turnover and cyanide detoxification might contribute to the release of sulfide in mitochondria. However, sulfide is a potent inhibitor of cytochrome c oxidase in mitochondria. Thus, efficient sulfide detoxification mechanisms are required in mitochondria to ensure adequate energy production and consequently survival of the plant cell. Two enzymes have been recently described to catalyze sulfide detoxification in mitochondria of Arabidopsis thaliana, O-acetylserine(thiol)lyase C (OAS-TL C), and the sulfur dioxygenase (SDO) ethylmalonic encephalopathy protein 1 (ETHE1). Biochemical characterization of sulfide producing and consuming enzymes in mitochondria of plants is fundamental to understand the regulatory network that enables mitochondrial sulfide homeostasis under nonstressed and stressed conditions. In this chapter, we provide established protocols to determine the activity of the sulfide releasing enzyme β-cyanoalanine synthase as well as sulfide-consuming enzymes OAS-TL and SDO. Additionally, we describe a reliable and efficient method to purify OAS-TL proteins from plant material.

Roles of Sulfur Metabolism and Rhodanese in Detoxification and Anti-Oxidative Stress Functions in the Liver: Responses to Radiation Exposure.

Organisms must confront various environmental stresses. The liver is central to protecting against such stresses in mammals, and it has many detoxification and anti-oxidative stress functions. Radiation is a source of oxidative stress and is known to affect the liver and induce anti-oxidative responses. The detoxification enzyme rhodanese, which is also called thiosulfate sulfurtransferase (TST), has been demonstrated to be induced in the liver in response to radiation. Cyanide detoxification is a function of the liver, and rhodanese is a key enzyme involved in sulfur metabolism in that detoxification. Though the anti-oxidative stress system in which sulfur molecules such as thiol compounds are involved has attracted attention as a defense against radiation, detoxification enzymes may have other roles in this defense. Understanding how these functions are affected by alterations of sulfur metabolism (including thiol compounds) after irradiation would help uncover their roles in defense against cancer and other deleterious health effects, as well as environmental stress responses. This article reviews the roles of sulfur-related metabolism in oxidative stress regulation and detoxification for recovery from liver damage after radiation exposure, with particular attention to recent findings of sulfur-related enzymes such as rhodanese, which is unique in sulfur metabolism.

Hierarchical hollow TiO2@CeO2 nanocube heterostructures for photocatalytic detoxification of cyanide

Hollow TiO2@CeO2 nanocubes are fabricated via a fast coordinating etching route. The hollow cubic nature and heterojunction effect of the nanostructure contribute greatly to the enhanced performance for photocatalytic detoxification of cyanide.

Statistical Enhancement of Cyanide Degradation Using Microbial Consortium

Remediation of cyanide contaminated water bodies using microorganisms is a popular alternative over chemical and physical methods of cyanide detoxification. The objective of the present study is to develop a microbial consortium using three bacteria, i.e., Enterobacter sp. RL2a, Serratia marcescencs RL2b and Achromobacter sp. RL2c for effective degradation of simulated cyanide wastewater. In vitro cyanide degradation was optimum with 2% inoculum volume of cells; pH 6.0, 30°C temperature at 20 mM substrate concentration leading to complete cyanide removal in 36 h. Response surface methodology (RSM) approach was used for optimization of reaction conditions for cyanide degradation using 5 mg ml-1 resting cells of microbial consortium. Plackett-burman design depicted that three variables viz. time, resting cells of strain RL2b and pH exhibit positive effect on cyanide degradation. The analysis of the quadratic regression model suggested that the model was very significant as correlation coefficient (0.847) closer to 1 denotes better correlation between the observed and predicted responses. The model was validated by performing the experiment under optimum conditions, which resulted in 63% cyanide degradation in 1 h reaction and complete degradation of 20 mM cyanide in 6 h. By performing factorial design, there was 1.3 fold (33%) increases in cyanide degradation.

Simultaneous overexpression of cyanidase and formate dehydrogenase in Arabidopsis thaliana chloroplasts enhanced cyanide metabolism and cyanide tolerance

Cyanide is a strong inhibitor of diverse metabolic reactions and easily absorbed by organisms. However, cyanide is also a byproduct of plant and microbial metabolism. This is why these groups of organisms contain pathways for cyanide detoxification. Large amounts of cyanides are also produced by industries and are today mostly removed by physical and chemical methods. Phytoremediation can provide an alternative to these techniques, but existing cyanide concentrations at contaminated sites often exceed the capacities of plant metabolism. In this study, we overexpressed a bacterial cyanidase together with a plant formate dehydrogenase in Arabidopsis thaliana in order to establish a synthetic pathway for cyanide degradation. Simultaneous overexpression of both enzymes would ultimately result in the formation of CO2 and NH3 from cyanide. Both enzymes were targeted to chloroplasts and shown to be active in planta. When plants were spray-inoculated with cyanide, overexpressors of the synthetic cyanide degradation pathway showed less reduction in leaf pigment contents, lower induction of antioxidant enzymes, and reduced growth retardation compared to controls. Growth on cyanide was also tested for seedlings germinating on agar, plants in hydroponics, and plants growing in sand. In all three assays, plants overexpressing the synthetic pathway for cyanide degradation showed enhanced growth and biomass accumulation compared to controls. Gas exchange measurements confirmed enhanced stress resistance of transgenic plants and suggested that cyanide degradation to CO2 increased the leaf internal CO2 concentration. Results are discussed in comparison to other approaches for cyanide phytoremediation.

Molecular cloning of rhodanese gene from soil metagenome of cold desert of North-West Himalayas: sequence and structural features of the rhodanese enzyme.

Rhodanese is a multifunctional, sulfur transferase that catalyzes the detoxification of cyanide by sulphuration in a double displacement (ping pong) mechanistic reaction. In the present study, small-insert metagenomic library from soil sample collected from Ladakh (3,000–3,600 m.a.s.l) in northwestern Himalayas, India was constructed. Function-driven screening of ~8,500 colonies led to the isolation of one esterase-positive clone (clone-est) harboring 2.43 kb insert. Sequence analysis of the insert identified two ORF’s, phosM encoding phosphoesterase and rodM encoding rhodanese. The 800 bp rodM gene encoded a polypeptide of 227 amino acids (RodM). The RodM showed maximum homology with the rhodanese-like protein from Cyanobacterium synechococcus species with a score identity of only 51 %. Putative 3D structure of RodM developed by homology modeling resembles to homodimeric protein of SUD sulfur transferase of Wolinella succinogenes with properly structured active-site cysteine (Cys) residue. Rhodanese has been reported from few culturable microorganisms.

S9-1 Sulfurtransferases and their role in hydrogen sulfide generation

The rhodanese superfamily (EC 2.8.1.x) includes tandem-domain thiosulfate:cyanide sulfurtransferase (TST, EC 2.8.1.1) and the strictly related 3-mercaptopyruvate:cyanide sulfurtransferase (MPST, EC 2.8.1.2). TST is the key enzyme, in the active center of which the persulfide group is created. The highly reactive sulfane sulfur atom of this group can be transferred to a substrate, e.g., cyanide detoxification, or can be passed to another protein acceptor participating in different cellular processes, e.g., biosynthesis of cofactors or thionucleosides. MPST transfers the sulfur atom from mercaptopyruvate, a product of cysteine transamination, to acceptors, such as cyanide (forming thiocyanate) or sulfite (forming thiosulfate – a sulfane sulfur-containing compound). Several metabolic reactions are known to generate sulfane sulfur in vitro , but their relative importance in vivo is not yet known. Current knowledge about sulfur donors assumes that the primary source of sulfane sulfur in eukaryotic cells relies on l -cysteine desulfuration pathway. Gamma-cystathionase (CTH, EC 4.4.1.1), an enzyme on the pathway, participates in endogenous production of H 2 S from l -cysteine. A product of CTH reaction, thiocystine, has been suggested to serve as the sulfane sulfur donor substrate for rhodanese. The potential role of the sulfane sulfur pool as an H 2 S reservoir and factors influencing the activity of sulfane sulfur-generating enzymes are under debate. The current study demonstrates that the MPST-dependent mitochondrial H 2 S-producing pathway is affected by oxidative stress, what may attenuate the production of H 2 S, and leads to various pathophysiological conditions. The intriguing problem is to identify possible sulfane sulfur donor(s) and/or acceptor(s), and to determine the regulatory role of sulfur in cellular metabolism.

A gene horizontally transferred from bacteria protects arthropods from host plant cyanide poisoning.

Cyanogenic glucosides are among the most widespread defense chemicals of plants. Upon plant tissue disruption, these glucosides are hydrolyzed to a reactive hydroxynitrile that releases toxic hydrogen cyanide (HCN). Yet many mite and lepidopteran species can thrive on plants defended by cyanogenic glucosides. The nature of the enzyme known to detoxify HCN to β-cyanoalanine in arthropods has remained enigmatic. Here we identify this enzyme by transcriptome analysis and functional expression. Phylogenetic analysis showed that the gene is a member of the cysteine synthase family horizontally transferred from bacteria to phytophagous mites and Lepidoptera. The recombinant mite enzyme had both β-cyanoalanine synthase and cysteine synthase activity but enzyme kinetics showed that cyanide detoxification activity was strongly favored. Our results therefore suggest that an ancient horizontal transfer of a gene originally involved in sulfur amino acid biosynthesis in bacteria was co-opted by herbivorous arthropods to detoxify plant produced cyanide.DOI: http://dx.doi.org/10.7554/eLife.02365.001.