Inhibitory Effect Of Cyanide Research Articles

Inhibitory Effects of Cyanide on the Activity of Granular Starch Hydrolyzing Enzyme (GSHE) during Hydrolysis of Cassava (Manihot Esculenta Crantz) Starch

The kinetics and inhibitory effects of cyanide on the granular starch hydrolyzing enzyme (GSHE) activity during hydrolysis of cassava (Manihot esculenta Crantz) starch at low temperature were studied. The substrates included native cassava starch at various concentrations (100-400 g/L) and native cassava starches with added cyanide at various concentrations (50-150 mg/kg), while the concentration of enzyme was 1.5% (w/w). A decrease in reducing sugar concentration during hydrolysis of cassava starch indicated that the cyanide reduced the enzyme activity. Lineweaver-Burk plot of Michaelis-Menten equation was used to study the inhibition kinetics. The maximum velocity (Vmax) value was higher for native cassava starch than that of native cassava starch with added cyanides. The presence of cyanide was found to reduce the Vmax values. No significant different of the saturation constant (Km) value between native cassava starch and native cassava starch with added cyanides was observed. Based on the inhibition type analysis, the effect of cyanide in the cassava starch can be classified as a noncompetitive inhibition, with the Ki value of 0.33 mg/L.

Inhibitory effect of cyanide on wastewater nitrification determined using SOUR and RNA-based gene-specific assays.

The effect of cyanide (CN(-) ) on nitrification was examined with samples from nitrifying bacterial enrichments using two different approaches: by measuring substrate (ammonia) specific oxygen uptake rates (SOUR), and by using RT-qPCR to quantify the transcripts of functional genes involved in nitrification. The nitrifying bioreactor was operated as a continuous reactor with a 24h hydraulic retention time. The samples were exposed in batch vessels to cyanide for a period of 12h. The concentrations of CN(-) used in the batch assays were 0·03, 0·06, 0·1 and 1·0mgl(-1) . There was considerable decrease in SOUR with increasing dosages of CN(-) . A decrease of more than 50% in nitrification activity was observed at 0·1mgl(-1) CN(-) . Based on the RT-qPCR data, there was notable reduction in the transcript levels of amoA and hao for increasing CN(-) dosage, which corresponded well with the ammonia oxidation activity measured via SOUR. The inhibitory effect of cyanide may be attributed to the affinity of cyanide to bind ferric haeme proteins, which disrupt protein structure and function. The correspondence between the relative expression offunctional genes and SOUR shown in this study demonstrates the efficacy of RNA-based function-specific assays for better understanding of the effect oftoxic compounds on nitrification activity in wastewater. The effect of cyanide on nitrifying bacteria was characterized by measuring physiological and transcriptional response. Cyanide was inhibitory to nitrification at concentrations that may be found in industrial waste. The RNA-based function-specific assays represent a mechanistic approach for better understanding the effect of toxic compounds on nitrification activity in wastewater. Moreover, the relative abundance of RNA transcripts can be used to closely track insitu nitrifying bacterial activity which can be used to predict inhibition events, thereby providing a metric to potentially improve performance of wastewater nitrifying systems.

Inhibitory effect of cyanide on nitrification process and its eliminating method in a suspended activated sludge process

Inhibition of nitrification by four typical pollutants (acrylonitrile, acrylic acid, acetonitrile and cyanide) in acrylonitrile wastewater was investigated. The inhibitory effect of cyanide on nitrification was strongest, with a 50% inhibitory concentration of 0.218 mg·gVSS-1 being observed in a municipal activated sludge system. However, the performance of nitrification was recovered when cyanide was completely degraded. The nitrification, which had been inhibited by 4.17 mg·gVSS-1 of free cyanide for 24 h, was recovered to greater than 95% of that without cyanide after 10 days of recovery. To overcome cyanide inhibition, cyanide-degrading bacteria were cultivated in a batch reactor by increasing the influent cyanide concentration in a stepwise manner, which resulted in an increase in the average cyanide degradation rate from 0.14 to 1.01 mg CN-·gVSS-1·h-1 over 20 days. The cultured cyanide-degrading bacteria were shaped like short rods, and the dominant cyanide-degrading bacteria strain was identified as Pseudomonas fluorescens NCIMB by PCR.

Upflow anaerobic sludge blanket treatment of starch wastewater containing cyanide.

Treatment of tapioca starch wastewater containing cyanide using an upflow anaerobic sludge blanket (UASB) process was investigated. Sludge from an anaerobic lagoon treating tapioca starch wastewater was used as seed. Performance of the UASB reactor with influent cyanide concentrations up to 25 mg/L was assessed. The inhibitory effects of cyanide were temporary and reversible. The process required longer recovery period for higher cyanide dosage. For 25 mg/L of cyanide concentration in the feed, the reactor required 15 days for complete recovery. Process performance was sensitive to operating parameters such as upflow velocity, cyanide loading rate, and chemical oxygen demand (COD) loading rate. A maximum cyanide loading rate of 0.38 kg/m3 x d was achieved in the process at a COD loading rate of 50 kg COD/m3 x d. Experiments with tapioca starch wastewater containing up to 10 mg/L of cyanide yielded satisfactory cyanide removal of approximately 93 to 98% and gas productivity of 7.5 m3/m3 x d with a COD loading rate of 30 to 40 kg COD/m3 x d.

Suppression of potassium currents by cyanide on the mouse motor nerve terminals

NaCn at low concentrations markedly depressed the potassium currents in the motor nerve terminal of mouse triangularis sterni neuromuscular junction pretreated with potassium channel blockers 4-aminopyridine (4-AP), tetraethylammonium (TEA) or glucose-free medium. Neither azide nor dinitrophenol nor ouabain mimicked the effect of cyanide. This inhibitory effect of cyanide on nerve terminal spikes was correlated to its dramatic increase in spontaneous transmitter release under glucose-free condition. These results suggest that the effect of cyanide on the electrogenesis of nerve terminals is due to the direct suppression of ATP-sensitive K + current since the effect was antagonized by ATP-sensitive K + channels opener diazoxide and this may modulate the transmitter release.

Inhibitory effects of cyanide on mechanical and electrical activities in the circular muscle of gastric antrum of guinea-pig stomach.

Effects of cyanide (CN) on spontaneous mechanical and electrical activities were studied in the circular muscle of the guinea-pig gastric antrum. CN (0.05-0.5 mM) inhibited both mechanical and electrical activities, but the inhibition was stronger in the former than the latter (slow wave). When glucose was removed for more than 30 min, slow wave was also blocked by CN. It is likely that ATP necessary for the generation of spontaneous activity can be supplied through either glycolysis or oxidative phosphorylation. CN slightly depolarized the membrane and the inhibition by CN was not affected by glibenclamide, a blocking agent of ATP-regulated K+ channel, suggesting that this channel is not activated by CN treatment. Basal level of intracellular Ca2+ measured with fura-2 tended to increase during the mechanical inhibition by CN. This was also clearly demonstrated in excess (60 mM) K+ solution. These results suggest that intracellular Ca2+ regulation is impaired and that there is uncoupling between intracellular Ca2+ and tension development in the presence of CN.

Activities of Isolated Mitochondria and Mitochondrial Enzymes from Aerobically and Anaerobically Germinated Barnyard Grass (Echinochloa) Seedlings

Activity of mitochondria isolated from whole seedlings of Echinochloa crus-galli (L.) Beauv. var oryzicola germinated under aerobic and anaerobic conditions for 5 to 7 days was investigated. Mitochondria from both treatments exhibited good respiratory control and ADP/O ratios. Although O(2) uptake was low in anaerobic mitochondria, activity rapidly increased when the seedlings were transferred to air. Mitochondria from both aerobically and anaerobically grown seedlings of E. crus-galli var oryzicola maintained up to 66% of their initial respiration rate in the presence of both cyanide and salicylhydroxamic acid, and the inhibitory effects of cyanide and azide were additive. In addition, antimycin A was not an effective inhibitor of respiration. Reduced-minus-oxidized absorption spectra revealed that cytochromes a, a(3), and b were reduced to a greater extent and cytochrome c was reduced to a lesser extent in anaerobically germinated seedlings relative to that in aerobically germinated seedlings. An absorption maximum in the cytochrome d region of the spectrum was reduced to the same extent under both germination conditions and an absorption maximum at 577 nm was present only in anaerobically germinated seedlings. Anaerobically germinated seedlings contained 70% of the cytochrome c oxidase activity found in air grown seedlings. Upon exposure to air, the developmental pattern of this enzyme in anaerobically germinated seedlings was similar to air controls. Succinate dehydrogenase activity in anaerobic seedlings was only 45% of the activity found in aerobically germinated seeds, but within 1 hour of exposure to air, the activity had increased to control levels. The results suggest that mitochondria isolated from E. crus-galli var oryzicola differ from other plants studied and that the potential for mitochondrial function during anaerobiosis exists.

Zygaenid moths, cyanide and thanatosis

Abstract Sensitivity of burnet mitochondria to cyanide was studied and some detoxifying mechanisms were investigated. Results showed that burnet mitochondria are relatively sensitive to KCN and that the inhibitory effects of cyanide can be completely reversed by pyruvate. Additionally, some glycolytic intermediates were determined in vivo at differential times from the beginning of the crushing‐induced thanatosis and at subsequent arousal. On the basis of our results, a hypothesis is suggested to explain both the well‐known resistance shown in vivo by burnets to hydrocyanic acid, and the biochemical mechanism at the root of thanatosis.

The effect of cyanide, SHAM and azide on the germination and respiration of Citrullus lanatus seeds

The germination of Citrullus lanatus seeds is inhibited by cyanide, azide and SHAM. Azide at a concentration of 0,5 mmol dm− 3 is sufficient to inhibit germination completely. Although azide is more effective than cyanide to inhibit germination, both substances inhibit respiration of these seeds to the same extent. The inhibitory effect of cyanide is antagonized by certain SHAM concentrations. No antagonism between azide and SHAM was found. These results imply that germination of C. lanatus seeds is controlled by a balance between cyanide sensitive and SHAM sensitive respiration and that azide and cyanide have different sites of action in inhibiting germination.

Surface charge on thylakoid membranes: regulation of photosynthetic electron transfer in cyanobacteria

The establishment of the steady-state rate of photosynthetic O2 evolution by cells of Anabaena variabilis and other cyanobacteria was found to be preceded by a lag-phase the duration of which depended on the time of cell preincubation in the dark. Electron acceptors (benzoquinone, N,N,N′,N′-tetramethyl-p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine or 2,6-dichlorophenolindophenol) abolished the lag-phase as well as the inhibitory effect of cyanide on electron transfer. Mono-, di-and trivalent cations added to the cell suspension markedly reduced the lag-phase. As cation concentrations were increased, acceleration and subsequent deceleration of the O2 evolution rate were observed. The efficient concentrations of cations decreased as their valency increased. The lag-phase and the rate of photosynthetic O2 evolution by the blue-green algae are suggested to depend on the value of the membrane surface charge governing the electrostatic interaction between unidentified membrane-bound redox components. The combination of valinomycin and nigericin as well as gramicidin D enhanced the duration of the lagphase by deenergization of thylakoid membrane.

The aerobic energy metabolism of the juvenile Fasciola hepatica

Juvenile Fasciola hepatica were isolated immediately after in vitro emergence from the metacecarial cysts and incubated with uniformly labelled glucose. Under aerobic conditions, carbon dioxide was the main end product of glucose breadkown. In the absence of oxygen, glucose was fermented mainly to propionate and acetate in a molar ratio of 2 : 1, with lactate as a minor product. This anaerobic end-product pattern closely resembles that of the adult liver fluke. In the presence of oxygen and 1 mM cyanide, lactate accumulated. The difference between anaerobic glucose breakdown and that in the presence of cyanide is explained by an inhibitory effect of cyanide on the malic enzyme (EC 1.1.1.40) of the juvenile mitochondria. A substantial Pasteur effect is calculated from these incubations. The oxygen consumption of the juveniles was completely cyanide-sensitive. From these results it is concluded that in aerobic conditions the juvenile liver flukes have an aerobic energy metabolism. Since they can survive prolonged periods of anaerobiosis, they should be called facultative anaerobes.

Mechanism of energy coupling for transport of deoxycytidine, uridine, uracil, adenine and hypoxanthine in Escherichia coli

The transport processes for uridine, deoxycytidine, uracil, adenine and hypoxanthine require an energy source and are active under anaerobic or aerobic conditions. Inhibitory effects of cyanide, arsenate, carbonylcyanide m- chlorophenylhydrazone , 2,4-dinitrophenol and N,N′- dicyclohexylcarbodiimide on the transport of uridine and deoxycytidine differ from the corresponding effects on the transport of uracil, adenine and hypoxanthine. The nature of these inhibitory effects supports the conclusion that uridine and deoxycytidine transport is energized either by electron transport or by ATP hydrolysis via (Ca 2+ + Mg 2+)-ATPase. The transport of uracil, adenine and hypoxanthine is dependent upon ATP or some high energy phosphate derivative of ATP, but is independent of (Ca 2+ + Mg 2+)-ATPase and electron transport. Uptake of the ribose moiety of uridine by a mutant of Escherichia coli B, which lacks the transport system for uracil and intact uridine, is neither stimulated by energy sources nor inhibited by various inhibitors of energy metabolism under either aerobic or anaerobic conditions.

Effect of Light Quality, Light Intensity and Temperature on Pigment Accumulation in Barley Seedlings

Active iiitochonidrial preparationls were obtained from the peel of young Faris sweet lemonis. The high buffer capacity of the grinding solution and the miiaintenanice of a slightly alkalinie reaction while griniding the tissues (lirectlv in the solutioni obviate(d inactivation of the mitochonidria usually associated with a low 1)H. Citric aci(d occurred in a lower concenitration thani niialic acid in the Faris sweet lemon. Oxidative phosphorylation was obtained with citrate, oa-ketoglutarate, succinate, and malate as substrates. Wlhen citrate-1, 5-C14 was used as a substrate. labeled aketoglutarate was found after 60 minutes and labeled malate after 120 minutes. When succinate-1, 4-C'4 was used as a substrate, malate and fumarate were found after 60 minutes and also citrate after 120 minutes. WVhen pyruvate-3-C'4 was used as a substrate together with a sparker acid. citrate, a-ketoglutarate, and malate were found after 120 minutes. These findings, together with the inhibitory effects of cyanide and malonate, indicated the citric acid cycle was operative in this variety of lemon.

CYANIDE INHIBITION AS A MEANS OF ELUCIDATING THE MECHANISMS OF CELLULAR RESPIRATION

CYANIDE INHIBITION AS A MEANS OF ELUCIDATING THE MECHANISMS OF CELLULAR RESPIRATION