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At least 1,603 records · Page 89Linked to original sources
PubMed1994

Efficacy and safety of atrioventricular nodal modification for atrioventricular nodal reentrant tachycardia in the pediatric population.

The safety and efficacy of radiofrequency catheter modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia in the pediatric population is described. Twenty-one patients with a mean age of 14.9 +/- 3.6 years underwent slow-pathway atrioventricular nodal modification with a stepwise anatomic approach. The average cumulative fluoroscopy exposure time (22 procedures in 21 patients) inclusive of the electrophysiologic study was 36.1 +/- 22 minutes. Noninducibility of tachycardia was achieved in all patients with one procedural complication (hemothorax). During a mean follow-up of 15 +/- 9.06 months, tachycardia recurred in one patient. Patient and family acceptance and satisfaction with the procedure was high. Because of the curative potential of radiofrequency catheter modification with low associated short- and long-term risks, it may be considered as a primary treatment option in pediatric patients with symptomatic atrioventricular nodal reentrant tachycardia.

Adolescent↗
PubMed1992

Conversion of typical to "atypical" atrioventricular nodal reentrant tachycardia after radiofrequency catheter modification of the atrioventricular junction.

Typical atrioventricular (AV) nodal reentry tachycardia (AVNRT) is characterized by anterograde activation over a slowly conducting pathway and by retrograde activation through a rapidly conducting pathway. Preliminary reports suggest that radiofrequency catheter modification can eliminate typical AVNRT while preserving anterograde conduction. Radiofrequency catheter modification was used to treat 88 patients with typical AVNRT. After baseline electrophysiologic evaluation, the ablation catheter was positioned proximal and superior to the site of maximal His deflection. Radiofrequency energy was applied until there was significant attenuation of retrograde conduction, and elimination of AVNRT inducibility. Eighty-one patients were successfully treated and form the basis of this report. A new paroxysmal supraventricular tachycardia with RP greater than PR interval was induced at electrophysiologic testing after successful ablation in 9 patients (11%). Mean atrial-His activation time was 140 +/- 31 ms, and the ventriculoatrial activation time was 170 +/- 46 ms. This arrhythmia was induced only with ventricular pacing during isoproterenol infusion and appeared to be mediated by AV nodal reentry. New retrograde dual AV nodal physiology after modification was more frequent in patients with atypical tachycardia than in those without (4 of 9 vs 2 of 72; p less than 0.0001). Although none of the patients were treated, only 1 of 9 had an episode of spontaneous atypical tachycardia during a mean follow-up of 12 months. Results of this study confirm that typical AVNRT can be rendered noninducible without the complete destruction of reentrant pathways. Because induction of "atypical" AVNRT was not predictive of spontaneous arrhythmia recurrence, it should not be an indication for additional ablation sessions or long-term drug therapy.

Adult↗
PubMed1988

Identifying inhibitors of queuine modification of tRNA in cultured cells.

Altered queuine modification of tRNA has been associated with cellular development, differentiation, and neoplastic transformation. Present methods of evaluating agents for their ability to induce queuine hypomodification of tRNA are tedious, time-consuming, and not readily amenable to examining cell-type or tissue specificity. Therefore, a rapid, small-scale assay was developed to identify agents that alter queuine modification of tRNA in cultured cells. Monolayer cultures (2cm2) of Chinese hamster embryo cells depleted of queuine for 24 h were evaluated for their ability to incorporate [3H]dihydroqueuine into acid precipitable material (tRNA) in the presence and absence of potential inhibitors. Known inhibitors of the queuine modification enzyme tRNA-guanine ribosyltransferase (e.g., 7-methylguanine, 6-thio-guanine, and 8-azaguanine) were very effective in blocking incorporation of the radiolabel, and the dose-dependent results exhibited small standard deviations in independent experiments. The data indicate that the method is rapid, reliable, and potentially useful with a variety of cell types.

Animals↗
PubMed1991

Optimizing myocardial hypothermia: II. Cooling jacket modifications and clinical results.

After induction of myocardial hypothermia by cold cardioplegic solution, myocardial rewarming occurs at 0.5 degrees to 1.0 degrees C/min. In addition to preventing myocardial rewarming from systemic and pulmonary venous return, continuous cooling of the myocardial surface must be provided. Modifications of a previously reported cooling jacket are described. These modifications include decreased width and thickness of the metal skeleton for easier application and increased malleability, respectively. Also, the double-row flow channel markedly minimizes obstruction of flow secondary to kinking and allows inlet and outlet lines to attach at adjacent points of the jacket thus minimizing obstruction of the operative field. The effectiveness of the jacket in 36 patients undergoing valve replacement and 19 patients having pulmonary thromboendarterectomy was evaluated by measurement of myocardial temperatures at multiple sites throughout aortic cross-clamping. Temperatures at all sites were maintained at 12 degrees C or less. Temperatures measured in phrenic nerve pedicles ranged from 25 degrees to 27 degrees C. During cooling, heat removal by the jacket was 330 calories/min. During maintenance of myocardial hypothermia, heat flow was 190 calories/min. Modifications of a cooling jacket facilitate usability and an array of sizes enhances applicability.

Body Temperature↗
PubMed1983

Arginine-specific modification of rabbit muscle phosphoglucose isomerase: differences in the inactivation by phenylglyoxal and butanedione and in the protection by substrate analogs.

Rabbit muscle phosphoglucose isomerase was modified with phenylglyoxal or 2,3-butanedione, the reaction with either reagent resulting in loss of enzymatic activity in a biphasic mode. At slightly alkaline pH butanedione was found to be approximately six times as effective as phenylglyoxal. The inactivation process could not be significantly reversed by removal of the modifier. Competitive inhibitors of the enzyme protected partially against loss of enzyme activity by either modification. The only kind of amino acid residue affected was arginine. However, more than one arginine residue per enzyme subunit was found to be susceptible to modification by the dicarbonyl reagents. From protection experiments it was concluded (i) that both modifiers react specifically with an arginine in the phosphoglucose isomerase active site and nonspecifically with one or more arginine residues elsewhere in the enzyme molecule, (ii) that modification at either loci causes loss of catalytic activity, and (iii) that butanedione has a higher preference for active site arginine than for arginine residues outside of the catalytic center whereas the opposite is true for phenylglyoxal.

Aldehydes↗
PubMed1984

Specific modification of the condensation domain of fatty acid synthase and the determination of the primary structure of the modified active site peptides.

Fatty acid synthase from the uropygial gland of goose was inactivated by iodoacetamide with a second-order rate constant of 1.3 M-1 S-1 at pH 6.0 and 25 degrees C. Of the seven component activities of the synthase, only the condensation activity was significantly inhibited by iodoacetamide modification. Since preincubation of the enzyme with acetyl-CoA, but not with malonyl-CoA, protected the enzyme from inactivation by iodoacetamide, it is suggested that iodoacetamide probably modified the primer-binding thiol group at the condensation active site. Determination of the stoichiometry of modification was done using [1-14C]iodoacetamide that was purified by high-performance liquid chromatography. Graphical analysis of the data showed that binding of 1.2 carboxamidomethyl groups per subunit of fatty acid synthase would result in complete inhibition of the enzyme activity, suggesting that there is one condensation domain per subunit of fatty acid synthase. Analysis of the tryptic peptide map of the enzyme that was modified with [1-14C]iodoacetamide in the presence and absence of acetyl-CoA revealed that acetyl-CoA prevented the labeling of a major radioactive peptide and a minor radioactive peptide. These two peptides were purified by high-performance liquid chromatography. Amino acid analysis of these two peptides revealed that the major radioactive peptide contained S-carboxymethylcysteine while the minor radioactive peptide did not. However, the latter peptide contained beta-alanine, suggesting that this peptide was from the acyl carrier protein segment of fatty acid synthase and that the iodoacetamide treatment resulted in modification of the pantetheine thiol, although to a lower extent than the primer-binding thiol. The sequence of the primer-binding active site peptide from the condensation domain was H2N-Gly-Pro-Ser-Leu-Ser-Ile-Asp- Thr-Ala-Cys(carboxamidomethyl)-X-Ser-Ser-Leu-Met-Ala-Leu-Glu-Asn-A la-Tyr-Lys- COOH, the first reported sequence of the condensation active site from a vertebrate fatty acid synthase. The acyl carrier protein segment showed extensive sequence homology with the acyl carrier protein of Escherichia coli, particularly in the vicinity of the phosphopantetheine attachment, and the sequence was H2N-Asp-Val-Ser-Ser-Leu- Asn-Ala-Asp-Ser-Thr-Leu-Ala-Asp-Leu-Gly-Leu-Asp-Ser(4'-phosphopanteth ein e) -Leu-Met-Gly-Val-Glu-Val-Arg-COOH.

Amino Acid Sequence↗
PubMed1984

Chemical modification of dipeptidyl peptidase iv: involvement of an essential tryptophan residue at the substrate binding site.

Inactivation of pig kidney dipeptidyl peptidase IV (EC 3.4.14.5) by photosensitization in the presence of methylene blue at pH 7.5 was observed to have pseudo-first-order kinetics. During the process, until over 95% inactivation was achieved, the histidine and tryptophan residues were decreased from 14.0 to 2.7 and 12.6 to 7.1, respectively, per 94,000-Da subunit, without any detectable changes in other photosensitive amino acids. Modification of four histidine residues per subunit using diethylpyrocarbonate resulted in only 30% inactivation of the enzyme, while N-bromosuccinimide almost completely inactivated the enzyme with the modification of only one tryptophan residue per subunit, as determined by absorption spectrophotometry at 280 nm. The protective action of the substrate and inhibitors such as Ala-Pro-Ala and Pro-Pro against the modification of tryptophan residues with N-bromosuccinimide was observed both fluorometrically and by measurement of activity. On the basis of these results it is suggested that one of the tryptophan residues in the enzyme subunit is essential for the functioning of the substrate binding site of pig kidney dipeptidyl peptidase IV.

Animals↗
PubMed1985

Inhibition of the functional interaction between fatty acid synthetase and thioesterase II by modification of a single cysteine thiol on the thioesterase.

Medium-chain S-acyl fatty acid synthetase thioester hydrolase (thioesterase II), a discrete, monomeric, serine active-site enzyme, modifies the product specificity of the de novo lipogenic pathway by hydrolyzing the thioester bond linking the growing acyl chain to the 4'-phosphopantetheine of the fatty acid synthetase. The mechanism of interaction of thioesterase II and fatty acid synthetase has been studied by probing the thioesterase with sulfhydryl-modifying reagents. Modification of a single cysteine thiol with 5,5'-dithiobisnitrobenzoate destroyed the ability of thioesterase II to catalyze hydrolysis of S-acyl fatty acid synthetase thioesters but had no effect on the ability of the enzyme to hydrolyze the model substrate, decanoyl-S-pantetheine. The inhibition was readily reversed on removal of the thionitrobenzoate moiety from the thioesterase with dithiothreitol. The results of kinetic experiments indicated that loss of the capacity of the thioesterase to hydrolyze the natural substrate could be attributed to an inability of the 5,5'-dithiobisnitrobenzoate-modified enzyme to bind to the fatty acid synthetase. Modification of the same cysteine thiol with methyl methanethiolsulfonate did not affect the ability of thioesterase II to hydrolyze either the natural or model substrates. The results are interpreted to indicate that cysteine thiol, remote from the catalytic active-site serine residue, is present on a binding domain of the thioesterase which interfaces with the fatty acid synthetase. Modification of this thiol with the large thionitrobenzoate moiety, but not with the small CH3S- moiety, inhibits the functional interaction either by steric hindrance or by perturbation of the polypeptide configuration at the binding domain.

Animals↗
PubMed1985

Modification of the active site of isocitrate lyase from watermelon cotyledons.

Isocitrate lyase (EC 4.1.3.1) from watermelon cotyledons was modified by diethylpyrocarbonate and by the affinity labels 3-bromopyruvate and itaconate epoxide. The reaction with diethylpyrocarbonate, carried out at 30 degrees C in sodium phosphate, pH 6.5, modified (per subunit) 5 histidines in the absence and 4 in the presence of substrate. The kinetics were nonsaturating with respect to diethylpyrocarbonate and the enzyme was protected against modification by substrate or both products together. Hydroxylamine (0.5 M) reversed both histidine modification and inactivation. The reaction with 3-bromopyruvate, carried out at 30 degrees C in 4-morpholinepropanesulfonic acid, pH 7.7, modified (per subunit) 1 sulfhydryl in the absence and 0 in the presence of substrate. The reaction showed saturation kinetics (KBrP = 1.4 X 10(-5)M) and Ds-isocitrate offers competitive protection (KI = 0.2-0.3 mM; Km = 0.25 mM). The reaction with itaconate epoxide, carried out at 30 degrees C in sodium phosphate, pH 7.0, was also saturating (KItEp = 16.4 mM) and the reversible inhibitor, itaconate (KI = 50 microM; Ki = 22.5 microM) as well as the product, succinate (KS = 10.4 mM; Ki = 4.5 mM) offer competitive protection. Hydroxylamine (1 M, pH 7.0) reversed inactivation of the enzyme, indicating modification of a carboxylate residue at the active site. In summary, three different amino acid residues have been modified in the active site domain of watermelon isocitrate lyase.

Affinity Labels↗
PubMed1986

Structure-function relationships in heparin cofactor II: chemical modification of arginine and tryptophan and demonstration of a two-domain structure.

Heparin cofactor II and antithrombin III are plasma proteins functionally similar in their ability to inhibit thrombin at accelerated rates in the presence of heparin. To further characterize the structural and functional properties of human heparin cofactor II as compared to antithrombin III, we studied the possible significance of arginyl and tryptophanyl residues and the changes in protein structure and activity during guanidinium chloride (GdmCl) denaturation. Both antithrombin and heparin cofactor activities of heparin cofactor II are inactivated by the arginine-specific reagent, 2,3-butanedione. Saturation kinetics are observed during modification and suggest formation of a reversible protease inhibitor-butanedione complex. Quantitation of arginyl residues following butanedione modification shows a loss of about four residues for total inactivation, one of which is essential for antithrombin activity. Arginine-modified heparin cofactor II did not bind to heparin-agarose and implies a role for the other modified arginyl residues during heparin cofactor activity. N-Bromosuccinimide oxidation (20 mol of reagent/mol of protein) of heparin cofactor II results in modification of approximately two tryptophanyl residues with no concomitant loss of heparin cofactor activity. Moreover, there is no enhancement of intrinsic protein fluorescence during heparin binding to the native inhibitor. Circular dichroism measurements show that the structural transition of heparin cofactor II during denaturation is distinctly biphasic, yielding midpoints at 0.6 and 2.6 M GdmCl. Functional protease inhibitory activities are affected to the same extent following denaturation-renaturation at various GdmCl concentrations. The results indicate that arginyl residues are critical for both antithrombin and heparin binding activities. In contrast, tryptophanyl residues are apparently not essential for heparin-dependent interactions. The results also suggest that heparin cofactor II contains two structural domains which unfold at different GdmCl concentrations.

Amino Acids↗
PubMed1986

Interaction of ferredoxin with ferredoxin:NADP reductase: effects of chemical modification of ferredoxin.

Chemical modification studies have been conducted on spinach ferredoxin to determine the nature of the groups on ferredoxin involved in its interaction with its reaction partners. Modification of a limited number (three or four) carboxyl groups or of the single histidine residue resulted in a decreased ability of ferredoxin to participate in NADP photoreduction but not in cytochrome c photoreduction, suggesting that these groups may be involved in interaction with ferredoxin:NADP reductase but are not involved in interaction with the reducing side of Photosystem I. In contrast, modification of amino groups or the single arginine residue on ferredoxin had little effect on the ability of ferredoxin to participate in NADP photoreduction, suggesting these groups are not involved in the interaction of ferredoxin with either ferredoxin:NADP reductase or the reducing side of Photosystem I. Attempts to modify tyrosine residues on ferredoxin resulted in destruction of the iron-sulfur center of the protein.

Arginine↗
PubMed1988

Maturation of asparagine-linked oligosaccharides in Dictyostelium discoideum analyzed with modification-specific probes.

Lysosomal enzymes in Dictyostelium discoideum contain high mannose oligosaccharides that contain mannose 6-phosphate and several unusual structures. The synthesis and distribution of these post-translational modifications were studied using probes for different carbohydrate groups. These probes include lectin-like antibodies directed to two distinct sulfated and one nonsulfated N-linked determinants, the lectin Con A, and the mammalian 215-kDa phosphomannosyl receptor. Only Con A binds to newly synthesized alpha-mannosidase present in the rough endoplasmic reticulum. The other modifications are acquired at different rates and are first detected on protein in light density Golgi-like membranes. Mutations which prevent protein transport to Golgi membranes block synthesis of these moieties, but inhibitors which prevent later transport steps have no effect. The majority of modified proteins are in lysosomes but significant amounts are delivered to nonlysosomal destinations. Different lysosomal proteins contain unequal amounts of each modification.

Animals↗
PubMed1988

Arginine chemical modification of Petunia hybrida 5-enol-pyruvylshikimate-3-phosphate synthase.

Reaction of Petunia hybrida 5-enol-pyruvylshikimate-3-phosphate synthase (EPSPS) with the arginine reagents phenylglyoxal (PGO) and p-hydroxyphenylglyoxal (HPGO) leads to inactivation of the enzyme. Inactivation with HPGO leads to modification of approximately 3 mol of arginine per mole of enzyme. The modification reaction follows pseudo-first-order kinetics with a t1/2 of 1 min at 5 mM p-hydroxyphenylglyoxal in 0.1 M triethanolamine HCl, pH 7.8. By titration of HPGO-modified enzyme with 5,5'-bis(dithio-2-nitrobenzoic acid), the possibility of cysteine modification by the arginine reagent was ruled out. While shikimate 3-phosphate (S3P) afforded partial protection to the enzyme against inactivation by HPGO, complete protection could be obtained by using a mixture of S3P and glyphosate. Under the latter conditions, only 1 mol arginine was modified per mole of enzyme. This pattern of reactivity suggests that two arginines may be involved in the binding of S3P and glyphosate to EPSP synthase. A third reactive arginine appears to be nonessential for EPSPS activity. Labeling of EPSP synthase with [14C]phenylglyoxal, peptic digestion, HPLC mapping, and amino acid sequencing indicate that Arg-28 and Arg-131 are two of the reactive arginines labeled with [14C]PGO.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1990

Modification of arginine residues in human growth hormone by 1,2-cyclohexanedione: effects on the binding capacity to lactogenic and somatogenic receptors.

Reactivity of arginine residues in human growth hormone was studied by reaction with 1,2-cyclohexanedione. Kinetic analysis of the data showed a good fit to a pseudo first order curve, with an apparent velocity constant k = 1.26 x 10(-2) min-1 and a maximum modification of 9.6 out of the 11 arginines of the molecule. Modification led to a decrease in binding capacity to both lactogenic and somatogenic rat liver receptors. In either case Tsou plots suggest that the modification of two arginine residues is responsible for this behavior, although it cannot be ascertained whether the two relevant residues are the same for both receptor types. Circular dichroism studies indicated no apparent changes in protein conformation in the modified hormone. Binding capacity was restored upon regeneration of arginines by incubation with Tris-HCl buffer. Only the carboxy-terminal peptide was isolated by HPLC from a tryptic digest of succinylated Arg-modified hGH, indicating that 183 is the nonreacting arginine residue.

Animals↗
PubMed1985

Evaluation and modification of spectrophotometric procedures for analysis of lactate dehydrogenase, beta-glucuronidase and arylsulphatase in human gingival crevicular fluid collected with filter-paper strips.

Filter-paper strips were used to collect GCF, and the sample eluted into a larger volume of diluent. This procedure allows for detection of site-to-site variation in GCF volume, and provides a 300-400 microliter sample for analysis of lactate dehydrogenase (LDH), beta-glucuronidase (BG) and arylsulphatase (AS) activities by a standard (serum) spectrophotometric assay modified for increased sensitivity. The results indicate that although the standard assay for LDH (based on oxidation of NADH) was adequate for detecting low activity in GCF samples, the modification doubled the sensitivity and allowed the use of less sample volume, thereby providing additional material for other assays. The standard assay for BG based on phenolphthalein being generated from phenophthalein glucuronic acid was not adequate for use in GCF analysis. The modification used increased assay sensitivity five-fold and allowed smaller samples to be used. The serum assay for AS (conversion of nitrocatechol sulphate to nitrocatechol) was accurate to the lower limit of AS activity in GCF and could be used without modification. The results emphasize the need to evaluate critically standard spectrophotometric assays for sensitivity when studying physiologically-collected GCF.

Adult↗
PubMed1986

Chemical modification and cross-linking as probes of regions on ferredoxin involved in its interaction with ferredoxin: NADP reductase.

Ferredoxin which had been modified with glycine ethylester in the presence of a water-soluble carbodiimide to the extent of one carboxyl-group modified per ferredoxin was subjected to peptide mapping in an attempt to locate the site(s) of modification. The peptide mapping was done by HPLC and analysis of the resulting chromatogram allowed assignment of peaks to various segments in the amino acid sequences of the two isozymes of ferredoxin. The modified ferredoxin appeared to be a mixture of ferredoxin derivatives in which modification had occurred in three areas of the molecule. Although unable to identify the specific residues modified, it has been shown that modification is localized in the regions of residues 26-30, 65-70, and 92-94. The possibility that these regions of ferredoxin may define its binding site for ferredoxin: NADP reductase is discussed. Peptide mapping studies on a covalently linked adduct between ferredoxin and ferredoxin: NADP reductase also support these regions of ferredoxin as being important in the interaction between the two proteins.

Amino Acid Sequence↗
PubMed1987

The effect of ethylenediamine chemical modification of plastocyanin on the rate of cytochrome f oxidation and P-700+ reduction.

Chemical modification of plastocyanin was carried out using ethylenediamine plus a water-soluble carbodiimide, which has the effect of replacing a negatively charged carboxylate group with a positively charged amino group at pH 6-8. The conditions were adjusted to produce a series of singly and doubly modified forms of plastocyanin. Differences in charge configuration allowed separation of these forms on a Pharmacia fast protein liquid chromatograph using a Mono Q anion exchange column. These forms were used to study the interaction of plastocyanin with its reaction partner cytochrome f. The rate of cytochrome f oxidation was progressively inhibited upon incorporation of increasing numbers of ethylenediamine moieties indicating a positively charged binding site on cytochrome f. However, differential inhibition was obtained for the various singly modified forms allowing mapping of the binding site on plastocyanin. The greatest inhibition was found for forms modified at negatively charged residues Nos. 42-45 and Nos. 59-61 which comprise a negative patch surrounding Tyr-83. In contrast, the form modified at residue No. 68, on the opposite side of the globular plastocyanin molecule, showed the least inhibition. It can be concluded that the binding site for cytochrome f is located in the vicinity of residues Nos. 42-45 and Nos. 59-61. Modification of plastocyanin at residues Nos. 42-45 showed no effect on the rate of P-700+ reduction, suggesting that these residues are not involved in the binding of Photosystem I. However, an increase in the rate of P-700+ reduction was observed for plastocyanins modified at residue No. 68 or Nos. 59-61, which is consistent with the idea that the reaction domain of Photosystem I is negatively charged and Photosystem I binds at the top of the molecule and accepts electrons via His-87 in plastocyanin. These results raise the possibility that plastocyanin can bind both cytochrome f and Photosystem I simultaneously. The effect of ethylenediamine modification on the formal potential of plastocyanin was also examined. The formal potential of control plastocyanin was found to be +372 +/- 5 mV vs. normal hydrogen electrode at pH 7. All modified forms showed a positive shift in formal potential. Singly modified forms showed increases in formal potentials between +8 and +18 mV with the largest increases being observed for plastocyanins modified at residues Nos. 42-45 or Nos. 59-61.

Amino Acid Sequence↗
PubMed1985

Latency studies on rat liver microsomal glucose-6-phosphatase. Correlation of membrane modification and solubilization by Triton X-114 with the enzymatic activity.

Interrelationships between the catalytic properties of glucose-6-phosphatase and the membrane structure of rat liver microsomes were investigated. Membrane modification and solubilization employing the nonionic surfactant Triton X-114 were standardized and analysed by ultracentrifugation, surface tension- and turbidity measurements. The effect of Triton X-114 on the glucose-6-phosphatase activity was studied systematically and the whole magnitude of time- and temperature-dependent inactivation of this enzyme has been demonstrated. The results show that the activity measured is always a resultant of two processes, the beginning of inactivation and the release of latency. Maximal activation of about 600% (83% of apparent latency) was obtained at 0 degree C. A correlation between membrane modification and solubilization and the conditions under preincubation and test incubation reveals that studies on detergent-disrupted microsomes are performed on structures reassembled from solubilizates and this implies a modified microenvironment in the reconstitutes. Kinetic analyses suggest interrelationships between Triton X-114 and the permeability barrier of the glucose-6-phosphatase system. At 0 degree C 2-propanol and ethanol are more potent tools for membrane modification than Triton X-114 and release 88% and 86% latent activity corresponding to an activation of the glucose-6-phosphatase of about 850% and 700%, respectively. These observations suggest that detergent treatment of microsomes could not preserve the functional integrity of the glucose-6-phosphate phosphohydrolase, which is one dogma of the substrate-transport hypothesis developed by Arion and his co-workers (Arion, W.J., et al. (1975) Mol. Cell. Biochem. 6, 75-83).

Animals↗