The response to drugs of gut muscle in asphyxia and in iodoacetic acid poisoning.
Explore the source record for details and available documents.
Journal Article↗
SEARCH · Search PubMed
Results for “Iodoacetates”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The aerobic metabolism of the isolated frog's heart poisoned by iodoacetic acid.
Explore the source record for details and available documents.
Journal Article↗
The effect of mono-iodoacetic acid on the absorption of water from glucose solutions in the subarachnoid space.
Explore the source record for details and available documents.
Journal Article↗
Effects of iodoacetic acid, glyceraldehyde and phosphorylated compounds on the small intestine of the rabbit.
Explore the source record for details and available documents.
Journal Article↗
Evidence for the presence of separate mechanisms regulating potassium and sodium distribution in Ulva lactuca.
1. The methods employed in these and preceding (25-27) studies were shown to allow analysis of true cellular sodium and potassium concentrations. 2. The rate of reaccumulation of potassium by potassium-deficient cells is independent of the presence or absence of sodium in the external medium. 3. Phenylurethane (10(-3)M), a photosynthetic and metabolic inhibitor, causes a marked progressive loss of potassium and gain of sodium, both of which changes are completely reversible on transferring the samples to running sea water. 4. Iodoacetate, while not effective in causing potassium and sodium shifts in the light, effects a loss of potassium and a gain of sodium in the light in the presence of phenylurethane. 5. Arsenate (5 x 10(-3)M) completely protects Ulva against the potassium loss usually observed with iodoacetate in the dark while it affords no protection against the sodium influx under the same conditions. Arsenate given after 18 to 20 hours in iodoacetate gives significant protection against potassium loss in the dark, and allows a slight net reaccumulation of potassium in the light. Arsenate in the dark after iodoacetate affords no protection against the sodium uptake caused by iodoacetate in the dark, while in the light under the same conditions sodium is rapidly secreted to the control level within a few hours. This resecretion of sodium is thought to be primarily an effect of light, the presence of arsenate being incidental. 6. The "decoupling agent" 4,6-dinitro-o-cresol causes a marked progressive increase in cellular sodium and a drop in cellular potassium, though the kinetics of these two movements are distinctly different from each other. 7. Pyruvate (50 mg. per cent) given with iodoacetate (2 x 10(-3)M) for 5 hours in the dark completely prevents the sodium increase caused by iodoacetate, while affording less protection against the potassium loss. Phosphoglycerate, on the other hand, offers more protection against potassium loss, and essentially none against the sodium gain. 8. ATP added in small amounts at short intervals to samples maintained in 10(-3)M iodoacetate in the dark affords significant protection against the potassium loss observed in iodoacetate. Cellular sodium is somewhat higher in the ATP-iodoacetate samples than in the iodoacetate samples. 9. In the discussion of the data presented two major points are emphasized: (1) the close correlation between cellular metabolism and normal cation control; (2) two mechanisms must be operative in cation regulation in this organism: one for moving potassium inwards and the other for transporting sodium outwards. These mechanisms are independent of each other.
Eukaryota↗
Evidence for a sulfhydryl group at the active site of serine transhydroxymethylase.
Iodoacetate reacts rapidly with one sulfhydryl group/subunit on aposerine transhydroxymethylase. The carboxymethylated apoenzyme does not recombine with pyridoxal 5'-phosphate. Under conditions used in the apoenzyme studies, the holoenzyme does not react to an appreciable extent with iodoacetate. The reaction of the apoenzyme with iodoacetate shows pseudo-first order kinetics with a half-life of about 3 min at 0 degrees C and pH 7.0. A pattern of saturation kinetics was found when increasing concentrations of iodoacetate were used. The half-maximum rate of inactivation occurred at 1.5 mM iodoacetate. Phosphate was observed to inhibit competitively the inactivation by iodoacetate with a Ki value of 1.8 mM. No inactivation of aposerine transhydroxymethylase was found when iodoacetamide was used in place of iodoacetate. These experiments suggest that removal of the pyridoxal 5'-phosphate from serine transhydroxymethylase exposes a reactive sulfhydryl group with a nearby cationic center which binds the carboxyl group of iodoacetate. The reactive sulfhydryl group was labeled with [14C]iodoacetate. From a chymotryptic digest, a 14C-containing peptide was isolated and determined to be: His-Pro-Lys-Leu-Ile-Ile-Ala-Gly-Thr-Ser-Cys(Cm)-Tyr.
Binding Sites↗
Glutamate efflux via the reversal of the sodium-dependent glutamate transporter caused by glycolytic inhibition in rat cultured astrocytes.
[3H]L-Glutamate uptake in cultured rat astrocytes was completely reduced by 30 min preincubation with 1 mM of iodoacetic acid, a glycolytic inhibitor. This treatment significantly reduced the energy charge potential, but did not cause membrane destruction in the cultured astrocytes. To examine the effect of iodoacetic acid on the glutamate release, [3H]L-glutamate was preloaded into astrocytes in the presence of methionine sulfoximine, a glutamine synthetase inhibitor, and the total intracellular radioactivity was measured after 30-min treatment with 1 mM iodoacetic acid for comparison with non-treated astrocytes. During the treatment, about 40% of the total intracellular glutamate content was effluxed. This efflux could be decreased by reducing the extracellular potassium ion concentration. The intracellular sodium concentration, measured with a sodium ion-sensitive fluorescent probe (sodium-binding benzofuran isophtalate), gradually increased to 30 mM on addition of 1 mM iodoacetic acid. These results indicate that the glutamate efflux via reversal of the Na(+)-dependent transporter occurred during glycolytic inhibition, and which may be caused by intracellular Na+ overload. Such an iodoacetic acid-induced Na+ overload could be completely diminished by pretreatment with 1 microM 5-[N- ethyl-N-isopropyl]amiloride, a selective Na(+)-H+ antiporter inhibitor, but even this did not stop the iodoacetic acid-induced glutamate efflux. The intracellular pH, measured by a pH-sensitive fluorescent probe [2',7'-bis(carboxyethy)-5,6-carboxy-fluorescein], was gradually decreased to 7.1 by the iodoacetic acid treatment. On the other hand, iodoacetic acid-induced intracellular acidosis was more rapid and severe in the presence of 5-[N-ethyl-N-isopropyl]amiloride. These results suggest that the reversal of the Na+-dependent glutamate transporter may be caused by not only intracellular Na+ overload but also intracellular acidosis.
ATP-Binding Cassette Transporters↗
Ionization-linked cooperative interactions in the active site of horse liver alcohol dehydrogenase.
Affinity labeling of horse liver alcohol dehydrogenase with iodoacetate in the presence of the activator imidazole has been studied from pH 6.1 to 10.5. The pH profiles for the dissociation constants of iodoacetate from the free enzyme and the enzyme-imidazole complex and of imidazole from the free enzyme and the binary enzyme-iodoacetate complex were determined. The variation with pH of the dissociation constants of iodoacetate (KI) and imidazole (KL) have in common a pKa of 8.6 assigned to the zinc-water ionization, and a pKa near 10. Lysine modification by ethyl acetimidate results in a higher affinity of iodoacetate to the enzyme at high pH as the pKa values of the lysine residues are increased. The binding of iodoacetate and imidazole at each enzyme subunit shows negative cooperativity at pH less than 9, with an interaction constant of 4.8 at pH 6.1. Positive cooperativity is observed at pH greater than 9, with an interaction constant of 0.5 at pH 10.5. The pH-dependent change in cooperativity results from the removal of the zinc-water ionization when imidazole becomes coordinated to the catalytic zinc ion. When iodoacetate binds at the anion binding site, a large perturbation of the zinc-water ionization is observed. Unlike imidazole, the binding of 1,10-orthophenanthroline and iodoacetate shows positive cooperativity at both pH 8.2 and 10.0 with an interaction constant as low as 0.06 at pH 10.0.
Alcohol Dehydrogenase↗
Modulation of the cytotoxicity and genotoxicity of the drinking water disinfection byproduct lodoacetic acid by suppressors of oxidative stress.
Drinking water disinfection byproducts (DBPs) are generated by the chemical disinfection of water and may pose a hazard to the public health. Previously we demonstrated that iodoacetic acid was the most cytotoxic and genotoxic DBP analyzed in a mammalian cell system. Little is known of the mechanisms of its genotoxicity. The involvement of oxidative stress in the toxicity of iodoacetic acid was analyzed with the antioxidants catalase and butylated hydroxyanisole (BHA). lodoacetic acid toxicity was quantitatively measured with and without antioxidants in Salmonella typhimurium strain TA100 and with Chinese hamster ovary (CHO) cells. The endpoints included cytotoxicity in S. typhimurium or in CHO cells, mutagenicity in S. typhimurium, and genotoxicity in CHO cells. Neither catalase nor BHA reduced the level of iodoacetic acid induced cytotoxicity in S. typhimurium. In CHO cells neither antioxidant caused a significant reduction in iodoacetic acid induced cytotoxicity. However, in S. typhimurium, BHA or catalase reduced the mutagenicity of iodoacetic acid by 33.5 and 26.8%, respectively. Likewise, BHA or catalase reduced iodoacetic acid induced genomic DNA damage by 86.5 and 42%, respectively. These results support the hypothesis that oxidative stress is involved in the induction of genotoxicity and mutagenicity by iodoacetic acid.
Animals↗
VIP-Related protection against lodoacetate toxicity in pheochromocytoma (PC12) cells: a model for ischemic/hypoxic injury.
To evaluate the protective properties of peptides related functionally and/or structurally to vasoactive intestinal peptide (VIP), PC12 cultures were treated with iodoacetate as a model for neuronal ischemic/hypoxic injury. Brain tissue can be pre-conditioned against lethal ischemia by several mechanisms including sub-lethal ischemia, moderate hypoglycemia, heat shock, and growth factors. In the present study, a superactive VIP lipophilic analog (Stearyl-Norleucine17-VIP; SNV) was used to pre-condition media of PC12 cells. After removal of the conditioned media, the cultures were exposed to iodoaceate, which inhibits glycolysis. Protective efficacy against iodoacetate-induced injury was assessed by the measurements of lactate dehydrogenase (LDH) activity in the media. Treatment with iodoacetate for 2.5 h produced a twofold increase in LDH activity in the media. The protective effect of SNV had an EC50 of 1 pM. Comparison of the preconditioning time required for full protection by SNV showed no apparent difference between a 15 min and a 2 h incubation period prior to the addition of iodoacetate. Iodoacetate treatment produced a 20% decrease in the RNA transcripts encoding activity-dependent neuroprotective protein (ADNP), a novel glia-derived protein that is regulated by VIP. The iodoacetate-associated reduction in ADNP mRNA was prevented by pre-treatment with SNV. These effects imply that SNV provides a regulatory mechanism for ADNP synthesis during glycolytic stress. Furthermore, a short exposure to SNV provided potent protection from iodoacetate-induced toxicity suggesting that SNV may have therapeutic value in the treatment of ischemic/hypoxic injury.
Animals↗
Localization of the 5-phospho-alpha-D-ribosyl-1-pyrophosphate binding site of human hypoxanthine-guanine phosphoribosyltransferase.
Human erythrocyte hypoxanthine-guanine phosphoribosyltransferase (HPRT) is inactivated by iodoacetate in the absence, but not in the presence, of the substrate, 5-phospho-alpha-D-ribosyl-1-pyrophosphate (PRib-PP). Treatment of HPRT with [14C]iodoacetate followed by tryptic digestion, peptide separation and sequencing has shown that Cys-22 reacts with iodoacetate only in the absence of PRib-PP; this strongly suggests that Cys-22 is in or near the PRib-PP binding site. In contrast, Cys-105 reacts with [14C]iodoacetate both in the presence and absence of PRib-PP. Carboxymethylation of Cys-22 resulted in an increase in the Km for PRib-PP, but no change in Vmax. Storage of HPRT also resulted in an increase in the Km for PRib-PP and a decrease in its susceptibility to inactivation by iodoacetate. Dialysis of stored enzyme against 1 mM dithiothreitol resulted in a marked decrease in Km for PRib-PP. The stoichiometry of the reaction of [14C]iodoacetate with Cys-22 in HPRT leading to inactivation (approx. 1 residue modified per tetramer) showed that, in this preparation of HPRT purified from erythrocytes, only about 25% of the Cys-22 side chains were present as free and accessible thiols. Titration of thiol groups [with 5,5'-dithiobis(2-nitrobenzoic acid)] and the effect of dithiothreitol on Km for PRib-PP indicate that oxidation of thiol groups occurs on storage of HPRT, even in the presence of 1 mM beta-mercaptoethanol.
Binding Sites↗
Function and reactivity of sulfhydryl groups of rat liver glycine methyltransferase.
Rat liver glycine methyltransferase is completely inactivated by 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). Treatment of the inactivated enzyme with KCN results in a reactivated enzyme having values of Vmax and S0.5 for S-adenosyl-L-methionine comparable to those of the native enzyme and about a 4-fold greater Km value for glycine. Kinetics of inactivation and reactivation show that one cysteine residue is involved in this process. Reaction of the methyltransferase with iodoacetate leads to partial inactivation of the enzyme; about 22% of the initial activity is retained in the modified enzyme. The relationship between the loss of enzyme activity and the number of iodoacetate molecules incorporated and the sequence analysis of peptides containing the modified residues indicate that carboxymethylation of Cys-282 is responsible for loss of activity. The observations that the activity of the cyanylated glycine methyltransferase shows no decrease upon incubation with iodoacetate and, conversely, the residual activity associated with the iodoacetate-modified enzyme is not abolished by DTNB suggest that Cys-282 is also involved in the inactivation by DTNB. Besides this residue, Cys-185, Cys-246, and Cys-262 are modified upon prolonged incubation with iodoacetate. 5'-[p-(Fluorosulfonyl)benzoyl]adenosine (FSBA) inactivates glycine methyltransferase by forming 1 disulfide/subunit [Fujioka, M., & Ishiguro, Y. (1986) J. Biol. Chem. 261, 6346-6351]. Despite this stoichiometry, treatment of the FSBA-inactivated enzyme with unlabeled iodoacetate and then with iodo[14C]acetate after reduction with 2-mercaptoethanol and subsequent peptide analysis show that the incorporated radioactivity is distributed equally among Cys-185, Cys-246, Cys-262, and Cys-282.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acids↗
The reaction of the soybean cotyledon mitochondrial cyanide-resistant oxidase with sulfhydryl reagents suggests that alpha-keto acid activation involves the formation of a thiohemiacetal.
The cyanide-resistant alternative oxidase of plant mitochondria is known to be activated by alpha-keto acids, such as pyruvate, and by the reduction of a disulfide bond that bridges the two subunits of the enzyme homodimer. When the regulatory cysteines are oxidized, the inactivated enzyme is much less responsive to pyruvate than when these groups are reduced. When soybean cotyledon mitochondria were isolated in the presence of iodoacetate or N-ethylmaleimide, the intermolecular disulfide bond did not form and the alternative oxidase was present only as a noncovalently associated dimer. N-Ethylmaleimide inhibited alternative oxidase activity, but iodoacetate was found to stimulate activity much like pyruvate, including enhancing the enzyme's apparent affinity for reduced ubiquinone. The presence of pyruvate or iodoacetate blocked inhibition of the enzyme by N-ethylmaleimide, indicating that all three compounds acted at the same sulfhydryl group on the alternative oxidase protein. The site of pyruvate and iodoacetate action was shown to be a different sulfhydryl than that involved in the redox-active regulatory disulfide bond, because iodoacetate bound to the alternative oxidase at the activating site even when the redox-active regulatory sulfhydryls were oxidized. Given the nature of the covalent adduct formed by the reaction of iodoacetate with sulfhydryls, the activation of the alternative oxidase by alpha-keto acids appears to involve the formation of a thiohemiacetal.
Acetals↗
Probing the active site of Tritrichomonas foetus hypoxanthine-guanine-xanthine phosphoribosyltransferase using covalent modification of cysteine residues.
The hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRTase) of Tritrichomonas foetus was inactivated by the thiol reagents iodoacetate and 5,5'-dithiobis(2-nitrobenzoic acid) (Nbs2). Iodoacetate inactivates the enzyme in a time-dependent and concentration-dependent manner that follows pseudo-first-order kinetics. However, the observation that total inactivation with iodoacetate was not achieved suggests that none of the reactive cysteine residues is directly involved in the catalytic activity of the enzyme. Nbs2 caused 50% inactivation rapidly, which was followed by gradual modifications of an additional three cysteine residues leading to complete enzyme inactivation. Analysis of the inactivation using the method developed by Tsou (1962) revealed that modification of two cysteine residues by Nbs2 is sufficient to impair the HGXPRTase activity. Tryptic digestion of HGXPRTase labeled with iodo[2-14C]acetic acid, followed by fractionation of the digest by HPLC and sequence analysis of the labeled peptides allowed the identification of Cys71, Cys129, Cys132, and Cys148 as the reactive cysteine residues. GMP and 5-phosphoribosyl-1-diphosphate provided complete protection against HGXPRTase inactivation by iodoacetate and against carboxymethylation of Cys129, Cys132, and Cys148, Cys71 was not protected by either substrate against iodoacetate, but its carboxymethylation caused no loss in enzyme activity either. There was also no substrate protection of Cys71 against Nbs2, which, however, caused 50% inactivation of the enzyme. Replacing the thionitrobenzoate (Nbs) moiety from Cys71 with cyanide resulted in a gradual recovery of the enzyme activity, which indicates that a steric hindrance at the active site was introduced by Nbs but removed by cyanide. Thus, our results demonstrate that although the reactive cysteine residues in HGXPRTase are not directly involved in the catalytic activity, modification of cysteine residues 129, 132, and 148 by iodoacetate or Nbs2 hinders substrate binding which can, in turn, protect the cysteine residues from modifications. The substrate protection of Cys129 and Cys148 is probably also indicative of a conformational change in the protein structure brought about by substrate binding.
Amino Acid Sequence↗
Active site labeling of a receptor-like protein tyrosine phosphatase.
The inactivation of the cytoplasmic domain of rat LAR, a receptor-like protein tyrosine phosphatase (PTPase), by iodoacetate and not by iodoacetamide suggested that iodoacetate interacts in a highly selective manner with the enzyme. The data indicate that iodoacetate binds at the active site of the enzyme with a stoichiometry of 0.8 mol of iodoacetate bound per mol of rat LAR. A single [14C]iodoacetate-labeled peptide was isolated following endoproteinase Lys-C digestion of the radiolabeled PTPase. Sequence analysis of the active site labeled peptide demonstrates that Cys-1522 contains the radiolabel. This residue has been shown by site-directed mutagenesis to be essential for rat LAR activity (Pot, D. A., Woodford, T. A., Remboutsika, E., Haun, R. S., and Dixon, J. E. (1991) J. Biol. Chem. 266, 19688-19696). Iodoacetate reacts only with the first domain of this double domain PTPase. These results, for the first time, directly identify the highly reactive cysteine residue at the active site of a PTPase and highlight the ability of this residue to participate as a nucleophile in the hydrolysis of phosphate from tyrosine.
Amino Acid Sequence↗
Cerebrolysin protects isolated cortical neurons from neurodegeneration after brief histotoxic hypoxia.
A brief period of histotoxic hypoxia exhibits certain metabolic features resembling the in vivo situation of ischemia. In this study the neuroprotective effects of the peptidergic nootropic drug Cerebrolysin (Cere) against iodoacetate induced histotoxic hypoxia were investigated. For that purpose isolated cortical neurons from 9 day chicken embryos were precultured with 0 to 6.4 mg.Cere/ml medium. At the 8th day in vitro histotoxic hypoxia was induced by incubation with 0.01 or 0.1 mM iodoacetate. Cells were allowed to recover from toxic stress for 3, 6, 24 or 48 hours. Cere protected neurons dose dependently from delayed neuronal cell death due to 0.01 mM iodoacetate even after a recovery period of 48h. After induction of histotoxic hypoxia by 0.1 mM iodoacetate high concentrations of Cere again led to neuronal protection after the 3 and 6 h recovery period. Moreover the influence of Cere on the cytoskeletal protein MAP2 in neurons submitted to 0.01 mM iodoacetate was investigated. With Western blotting and immunohistochemical techniques it has been demonstrated that the drug clearly increased MAP2 abundance after histotoxic hypoxia. The present study points out that after severe damage of cortical neurons with iodoacetate Cere is able to protect neurons from delayed neuronal cell death maybe by maintaining neuronal plasticity due to avoidance of the cytoskeletal breakdown.
Amino Acids↗
The functional recovery of post-ischemic myocardium requires glycolysis during early reperfusion.
Glycolysis normally provides only a small fraction of myocardial ATP production, but ATP from glycolysis may be preferentially used to support membrane activities such as ion pumping. Since ion homeostasis is disturbed during ischemia, glycolysis may be particularly important in the recovery of postischemic myocardium. This hypothesis was investigated in isovolumic, isolated rabbit hearts, perfused with 16 mM glucose, 5 mM pyruvate or 5 mM acetate. Global left ventricular function (rate-pressure product, RPP) and unidirectional ATP synthesis rate (P(i)-->ATP flux, 31P NMR) were measured before and after 20 min global ischemia. Control hearts with intact glycolysis were compared with hearts which had glycolysis inhibited by iodoacetate (150 microM), 2-deoxyglucose (10 mM) or prior glycogen depletion. In normal hearts, inhibition of glycolysis had no effect on function when pyruvate or acetate was present as as a carbon substrate. In post-ischemic hearts, reperfusion with glucose (n = 7) resulted in moderate recovery of function to about 65% of pre-ischemic levels after 1 h reperfusion. Administration of iodoacetate at the onset of reperfusion to hearts receiving pyruvate or acetate resulted in much worse functional recovery and a marked rise in left ventricular end-diastolic pressure (LVEDP). With pyruvate (n = 7), RPP recovered to 27% of pre-ischemic levels, while mean LVEDP increased to 34 mmHg (vs 16 mmHg with glucose); with acetate (n = 6), RPP returned to 31% of pre-ischemic levels, while mean LVEDP rose to 32 mmHg. The ratio of P(i)-->ATP flux to atoms of oxygen consumed (P:O ratio) was 2.14 +/- 0.36 in hearts reperfused with iodoacetate and pyruvate, consistent with partial mitochondrial uncoupling. However, if inhibition of glycolysis with iodoacetate was delayed until after 30 min reperfusion, recovery of hearts reperfused with pyruvate was similar to hearts perfused with glucose, and there was no evidence of mitochondrial uncoupling (P:O ratio = 2.95 +/- 0.33). Inhibition of glycolysis during reperfusion with 2-deoxyglucose yielded results similar to reperfusion with iodoacetate. The worst recovery was observed in hearts with combined glycolytic inhibition by pre-ischemic glycogen depletion and iodoacetate during reperfusion (RPP = 13% of pre-ischemic levels). These findings indicate that glycolysis plays a crucial role during early reperfusion in the functional and metabolic recovery of post-ischemic myocardium.
Adenosine Triphosphate↗
Immobilization ameliorates chemically-induced articular cartilage damage.
We have previously shown that immobilization protects against the development of mechanically-induced osteoarthritis following-anterior cruciate ligament transection in dogs. Herein, we examine the effect of immobilization of the leg on the chemically-induced degeneration of femoral articular cartilage caused by intraarticular injection of iodoacetate in guinea pigs. One week after the injection, cartilage from animals which were not immobilized exhibited a decrease in Safranin O staining and a 10-20% reduction in the number of chondrocytes. Three weeks after injection, cell death and loss of Safranin O staining had progressed, and surface fibrillation and osteophytes had developed. Articular cartilage from the contralateral (uninjected) knees of guinea pigs which received iodoacetate, and from knees of animals which were immobilized for 1 week but did not receive iodoacetate, was histologically and histochemically normal. However, specimens from 2 of 4 untreated knees which were immobilized for 3 weeks showed a reduction in Safranin O staining. Immobilization of the knee did not alter the loss of Safranin O staining seen after intraarticular iodoacetate injection, but did reduce the depletion of chondrocytes (P less than 0.05). Furthermore, neither osteophytes nor fibrillation developed in any of the animals which were constrained after iodoacetate injection. Thus, immobilization was clearly protective in this model of chemically-induced cartilage injury.
Animals↗