3-Mercaptopyruvate sulfurtransferase: an enzyme at the crossroads of sulfane sulfur trafficking

Abstract3-Mercaptopyruvate sulfurtransferase (MPST) catalyzes the desulfuration of 3-mercaptopyruvate to generate an enzyme-bound hydropersulfide. Subsequently, MPST transfers the persulfide’s outer sulfur atom to proteins or small molecule acceptors. MPST activity is known to be involved in hydrogen sulfide generation, tRNA thiolation, protein urmylation and cyanide detoxification. Tissue-specific changes in MPST expression correlate with ageing and the development of metabolic disease. Deletion and overexpression experiments suggest that MPST contributes to oxidative stress resistance, mitochondrial respiratory function and the regulation of fatty acid metabolism. However, the role and regulation of MPST in the larger physiological context remain to be understood.

Physicochemical Properties of 3-Mercaptopyruvate Sulfurtransferase: A Cyanide Detoxifying Enzyme from the Hemolymph of Limicolaria flammae (Garden Snail)

Background: 3-Mercaptopyruvate sulfurtransferase (3-MST) is a multifunctional, mitochondrial and cytoplasmic sulphurtransferase that catalyses the detoxification of cyanide to a less toxic thiocyanate. Limicolaria flammea feeds majorly on green leaves, plants and other cyanide containing foods. Methods: 3-MST from the hemolymph of Limicolaria flammae was purified by 70 % ammonium sulphate precipitation and ion exchange chromatography. The purified enzyme was characterized at different levels such as optimal activity, inhibitors, substrate preference, thermal stability and analysis of ki-netic parameters. Results: 3-MST from the hemolymph of Limicolaria flammae had a yield of 0.75 % with specific activity of 0.42 μ/mg/ml. The Km values for the substrates; KCN and 2-Mercaptoethanol were 1.09 and 2.83 mM, while the Vmax values were 3.08 μml/mol/min and 6.17 μml/mol/min respectively. The optimum pH and temperature of the enzyme were 5.0 and 60° C respectively. The metals (Al3+, Ca2+, and K+) demonstrated inhibitory activity in a concentration dependent manner. The substrate specificity study showed that sodium sulphite, ammonium per sulphate and ammonium sulphite showed enzymatic interference. Conclusion: This study affirmed the presence of 3-MST activity in the hemolymph of Limicolaria flammea, an indication that the enzyme possesses functional cyanide detoxification mechanism necessary for the survival of the animal in the environment.

Metabolism of the Cyanogenic Glucosides in Developing Flax: Metabolic Analysis, and Expression Pattern of Genes

Cyanogenic glucosides (CG), the monoglycosides linamarin and lotaustralin, as well as the diglucosides linustatin and neolinustatin, have been identified in flax. The roles of CG and hydrogen cyanide (HCN), specifically the product of their breakdown, differ and are understood only to a certain extent. HCN is toxic to aerobic organisms as a respiratory inhibitor and to enzymes containing heavy metals. On the other hand, CG and HCN are important factors in the plant defense system against herbivores, insects and pathogens. In this study, fluctuations in CG levels during flax growth and development (using UPLC) and the expression of genes encoding key enzymes for their metabolism (valine N-monooxygenase, linamarase, cyanoalanine nitrilase and cyanoalanine synthase) using RT-PCR were analyzed. Linola cultivar and transgenic plants characterized by increased levels of sulfur amino acids were analyzed. This enabled the demonstration of a significant relationship between the cyanide detoxification process and general metabolism. Cyanogenic glucosides are used as nitrogen-containing precursors for the synthesis of amino acids, proteins and amines. Therefore, they not only perform protective functions against herbivores but are general plant growth regulators, especially since changes in their level have been shown to be strongly correlated with significant stages of plant development.

Pengaruh Penambahan H2O2 dan Na2S2O5 pada Proses Detoksifikasi Tailing Hasil Pelindian Emas

Abstrak. Proses ekstraksi emas dan perak melalui metode pelarutan selektif menggunakan reagen sianida merupakan proses pengolahan yang umum digunakan saat ini. Salah satu tantangan yang hadir dengan pemanfaatan proses pelindian adalah kontrol kandungan weak acid dissociable cyanide (WAD CN) pada tailing hasil proses pelindian guna menghindari terjadinya pencemaran lingkungan. Berdasarkan standar yang ditetapkan oleh International Cyanide Management Institute (ICMI), kandungan sianida yang diperbolehkan untuk dibuang bersama tailing ke lingkungan sebesar <50 ppm. Rangkaian proses yang harus dilakukan untuk menekan kandungan WAD CN pada tailing adalah melalui proses cyanide detoxification. Proses detoksifikasi yang dilakuan adalah dengan menambahkan oksidator berupa H2O2 dan kombinasi dengan Na2S2O5 (sodium metabisulphide/SMBS) dengan rasio H2O2:CN sebesar 2:1, 5:1, 10:1, dan 20:1, serta penambahan SMBS dengan rasio antara SO2:CN sebesar 4:1 dalam sebuah bottle roll. Penambahan SMBS bertujuan untuk menurunkan jumlah penggunaan oksidator H2O2 yang digunakan. Berdasarkan analisis yang dilakukan diketahui bahwa semakin besar perbandingan antara H2O2:CN maka semakin rendah WAD CN yang dihasilkan, dari 84 ppm sebelum adanya penambahan oksidator menjadi 0,18 ppm pada rasio penambahan 20:1. Selain itu penambahan Na2S2O5 juga menyebabkan penurunan kandungan WAD CN yang lebih signifikan menjadi 0,31 ppm pada rasio H2O2:CN sebesar 5:1. Adapun variasi pH tidak menunjukkan pengaruh yang signifikan terhadap kadar WAD CN pada saat proses detoksifikasi. Kata kunci: sianidasi, detoksifikasi sianida, wastewater treatment, pelindian emas. Abstract. The Effect of H2O2 and Na2S2O5 Addition in Cyanide Detoxification from Leached-Gold Tailing. Cyanide leaching is the predominant process of gold and silver extraction in large scale mining. The most challenging part related to leaching process of cyanide is controlling the content of weak acid dissociable cyanide (WAD CN) in tailing to prevent environmental pollution. The International Cyanide Management Institute (ICMI) has determinded the cyanide content allowed to be disposed of with tailings into the environment should not more than 50 ppm. Content of WAD CN in tailing can be suppressed by cyanide detoxification process. Detoxification process was conducted by adding H2O2 as an oxidizing agent into the tailings with varying H2O2:CN ratio (2:1, 5:1, 10:1, and 20:1) and combining with the addition of Na2S2O5 (sodium metabisulphide/SMBS) with SO2:CN ratio of 4:1 in a bottle roll. The study showed that the greater the ratio of H2O2:CN, the lower the WAD CN remained in tailing, from 84 ppm before any addition of oxiding agent to 0.18 ppm at ratio of 20:1. Moreover, Na2S2O5 addition was also significantly reduced WAD CN content down to 0.31 ppm at H2O2:CN ratio of 5:1. It also has been identified that pH variation has no significant impact to WAD CN content during detoxification process. Keywords: cyanidation, cyanide detoxification, wastewater treatment, gold leaching. Graphical Abstract

Cyanide detoxification efficiency of injection and soak of hydroxocobalamin, sodium nitrite and sodium thiosulfate for sea water ornamental fish

The Oceanographic Museum offers interesting exhibits of several marine lives for tourist sightseeing and entertainment. These sea water ornamental fish are all caught in the wild. However, its health can be affected by cyanide poisoning during human fishing. Depending on the level of cyanide poisoning, fish can die after one and two weeks that caused economic damages for the museum. The present study is concerned with results of cyanide detoxification by using direct injection into cinnamon clownfish or soak of hydroxocobalamin, sodium nitrite and sodium thiosulfate with the aim of improving the health, survival and life time for fish, contributing to increasing economic efficiency for the Oceanographic Museum.

Screening for rhodanese producing Bacterium in freshly pressed Cassava effluents of a Cassava processing industry channeled to Odo-Oba Stream in Ogbomoso-Nigeria

Rhodanese is a key enzyme that plays an important role in cyanide detoxification. The enzyme was extracted, purified and physico-chemically characterised from Bacillus licheniformis which demonstrated the highest efficacy compared to the seven isolates of bacteria of the cassava processing industry effluent morpholologically and biochemically characterised. Statistical analysis was performed using one-way ANOVA and values were considered significant at p<0.05. This study showed that the optimum growth temperature was 350C at a pH 9.0. The highest duration time for the synthesis of rhodanese was at 40 hours. Potassium cyanide (KCN) and casein were the best carbon and nitrogen sources. The enzyme has a specific activity of 10.99 RU/mg, with a purification fold of 4.38, a percentage yield of 15.96%. The apparent Km for KCN and Sodium thiosulphate (Na2S2O3) were determined to be 30.24mM and 24.93mM respectively while their Vmax were 5.40 RU /ml/min and 5.07 RU /ml/min respectively. The optimum pH and temperature were 8.0 and 50 0C respectively. The enzyme showed a high stability at 500C. The enzyme showed specificity at 6.78 RU/ml/min for Na2S2O3 while it was inhibited by other sulphur containing substrates namely 2-mercaptoethanol, ammonium persulphate, and sodium metabisulphite The enzyme activity was not inhibited by metal ions such as (K+, Mg2+, Ba2+, Ni2+, Sn2+ and Na+) at 1mM and 10mM and was not significant (p>0.05). Therefore, B. licheniformis have the potentials of reducing cyanide pollution thereby enhancing effective management of cassava mill effluent before eventual discharge into the environment and this may be developed into a more effective tool for bioremediation.

Photochemical Degradation of Cyanides and Thiocyanates from an Industrial Wastewater

We have explored the simultaneous degradation of cyanides and thiocyanate present in wastewaters from a cokemaking factory using photoassisted methods under varied illumination conditions (from simulated solar light to UV light). Overall, the photochemical degradation of cyanides was more efficient than that of thiocyanates, regardless of the illumination conditions, the effect being more pronounced in the absence of a photocatalyst. This is due to their different degradation mechanism that in the case of thiocyanates is dominated by fast recombination reactions and/or charge transfer reactions to electron scavengers. In all cases, cyanate, ammonia, nitrates, and nitrites were formed at different amounts depending on the illumination conditions. The conversion yield under simulated solar light was almost complete for cyanides and quite high for thiocyanates after 6 h of illumination. Regarding toxicity, photochemical oxidation at 254 nm and under simulated solar light decreased significantly the toxicity of the pristine wastewater, showing a correlation with the intensity of the irradiation source. This indicate that simulated light can be effectively used to reduce the toxicity of industrial effluents, opening an interesting perspective for optimizing cyanide detoxification systems based on natural light.