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Results for “Enzyme Reactivators”

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PubMed2004

Association between elevated liver enzymes and C-reactive protein: possible hepatic contribution to systemic inflammation in the metabolic syndrome.

OBJECTIVE: The objective of this study was to test whether the frequent association between liver enzyme elevations and various components of the metabolic syndrome is associated with higher C-reactive protein (CRP) levels. METHODS AND RESULTS: Alanine aminotransferase (ALT), alkaline phosphatase (Alk-P), and high-sensitivity CRP were measured in 1740 subjects. Adjusted geometric mean CRP was calculated for subjects with normal and elevated ALT and for subjects with normal and elevated Alk-P, adjusting for age, sex, smoking, physical activity, body mass index, fasting glucose, triglycerides, the presence of hypertension and low HDL cholesterol, and use of aspirin or hormone replacement therapy. Adjusted CRP levels were higher in subjects with elevated ALT (2.21 versus 1.94 mg/L, P=0.028) or elevated Alk-P (2.58 versus 1.66 mg/L, P<0.0001). Logistic regression showed that compared with subjects with normal liver function tests, the adjusted odds for high-risk CRP (>3 mg/L) were significantly higher in subjects with elevated ALT (OR, 1.5; 95% CI, 1.2 to 1.9, P=0.002) or elevated Alk-P (OR, 2.1; 95% CI, 1.7 to 2.6, P<0.0001). CONCLUSIONS: Elevations of liver enzymes are associated with higher CRP concentrations. Hepatic inflammation secondary to liver steatosis is a potential contributor to the low-grade inflammation associated with the metabolic syndrome.

Alanine Transaminase↗

PubMedDate not supplied

Activity of some lysosomal enzymes and postnatal ontogenetic development of epileptic reactivity in rabbit brain.

The beta-glycerophosphatase (GP), p-nitrophenyl phosphatase (PNFP) and beta-glucuronidase (BG) activities in four neocortical rabbit areas have been determined in six successive electrocorticographic stages of postnatal ontogenetic development of epileptic reactivity. The lysosomal enzyme activity decreases gradually from rabbits aged 1 day to adult ones and is similar within the four neocortical areas. The activity of the three lysosomal enzymes is not parallel. Statistically significant decreases in beta-glycerophosphatase activity are present in rabbits at the age of 30 days versus adult age in all the areas investigated while beta-glucuronidase is higher at the same developmental stage only in beta retrosplenial (III) and motor (II) areas. Correlation of the electrophysiological and biochemical data cannot provide explanation for the particular phenomena of the epileptogenic reactivity in rabbit cerebral neocortex.

4-Nitrophenylphosphatase↗

PubMed1997

Converting enzyme inhibitor improves forearm reactive hyperemia in essential hypertension.

Endothelial function is known to be impaired in essential hypertensive patients. In this study, we examined whether antihypertensive drugs improve forearm vasodilatory response to reactive hyperemia in 26 patients with essential hypertension (62 +/- 2 years) without diabetes mellitus, hyperlipidemia, coronary heart disease, or cerebrovascular disease. Antihypertensive drugs were never given or were discontinued for at least 4 weeks before the study. Patients were treated with monotherapy of either temocapril (2 or 4 mg, n = 15) or amlodipine (2.5 or 5 mg, n = 11) for 6 months. Forearm blood flow was measured by strain-gauge plethysmography. Vasodilator response to the release of upper arm compression at 300 mm Hg for 5 minutes and to sublingual administration of nitroglycerin (0.3 mg) were assessed. Changes of forearm blood flow response to reactive hyperemia were significantly less in hypertensive patients (99 +/- 18%) than in age-matched normotensive control subjects (150 +/- 22%, P < .01, n = 39). Blood pressure (mm Hg) was similarly decreased by the treatment with temocapril (160 +/- 4/94 +/- 2 to 139 +/- 3/83 +/- 3, P < .001) or amlodipine (165 +/- 5/94 +/- 3 to 141 +/- 4/82 +/- 3, P < .001). Response to nitroglycerin was not changed by either drug. Forearm vasodilatory response to reactive hyperemia was improved by temocapril (102 +/- 20% to 168 +/- 25%, P < .01) but not by amlodipine (97 +/- 16% to 114 +/- 14%, NS). These results indicate that the treatment with the angiotensin-converting enzyme inhibitor temocapril improved forearm vasodilatory response to reactive hyperemia, suggesting its beneficial effect on endothelial function.

Aged↗

PubMed1990

Reactive oxygen intermediates metabolizing enzymes in Ancylostoma ceylanicum and Nippostrongylus brasiliensis.

Adult worms of Ancylostoma ceylanicum and Nippostronglyus brasiliensis were found to possess an active system for the detoxification of reactive oxygen intermediates. Xanthine oxidase, which is known to produce superoxide anion, was detected in both the nematode parasites in significant activities. Superoxide anion, thus produced, may quickly be eliminated by superoxide dismutase. Both parasites also exhibited the presence of catalase, peroxidase, and glutathione peroxidase for efficient removal of hydrogen peroxide. Glutathione reductase and glucose-6-phosphate dehydrogenase were, however, detected in low levels of activities. Endowment of A. ceylanicum and N. brasiliensis with these antioxidant enzymes, therefore, enables them to evade the host's effector mechanism for their survival. Superoxide dismutase of both these nematodes showed marked inhibition by KCN and, hence, the enzyme appears to be of copper-zinc type.

Ancylostoma↗

PubMed1993

Inactivation of penicillin acylase from Kluyvera citrophila by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline: a case of time-dependent non-covalent enzyme inhibition.

Penicillin acylase (PA) from Kluyvera citrophila was inhibited by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), a specific carboxy-group-reactive reagent. Enzyme activity progressively decreased to a residual value depending on EEDQ concentration. Neither enzymic nor non-enzymic decomposition of EEDQ is concomitant with PA inactivation. Moreover, enzyme re-activation is achieved by chromatographic removal of EEDQ, pH increase or displacement of the reagent with penicillin G. It was then concluded that PA inactivation is due to an equilibrium reaction. The kinetics of enzyme inactivation was analysed by fitting data to theoretical equations derived in accordance with this mechanism. Corrections for re-activation during the enzyme assay were a necessary introduction. The pH-dependence of the rate constant for EEDQ hydrolysis either alone or in the presence of enzyme was studied by u.v. spectroscopy. It turned out to be coincident with the pH-dependence of the forward and reverse rate constants for the inactivation process. It is suggested that previous protonation of the EEDQ molecule is required for these reactions to occur. The thermodynamic values associated with the overall reaction showed little change. Finally it is proposed that the inactivation of PA by EEDQ proceeds through a two-step reaction. The initial and rapid reversible binding is followed by a slow, time-dependent, non-covalent, reversible inactivating step. The expected behaviour in the case of enzyme modification by covalent activation of carboxy residues is also reviewed.

Enterobacteriaceae↗

PubMed1980

Some new reactive polymers for the immobilization of enzymes.

From poly(vinyl alcohol) precursors, various reactive carriers for the immobilization of enzymes were synthesized. As insoluble starting polymers, the following products were used: poly(vinyl alcohol), gels crosslinked with terephthalaldehyde, hydrolyzed beads of crosslinked poly(vinyl acetate), poly(vinyl acetate-co- ethylene) tubes coated with poly(vinyl alcohol), and poly(vinyl alcohol)-containing synthetic pulp. Reactive groups introduced into these carriers or methods for their activation included the diazonium- and isothiocyanato group, and the glutardialdehyde-, BrCN, 2, 4, 6-trichloro-s-triazien, and p-benzoquinone methods. Furthermore, SH-specific reactive groups such as N-substituted maleimide groups or activated mixed disulfides with 2-thiopyridyl groups could be introduced into PVA-polymers. Enzymes like hydrolases (e.g. papain, trypsin, chymotrypsin, urease), oxidoreductases (e.g. glucose oxydase, catalase, glucose-6-phosphate dehydrogenase) as well as the example of transferase hexokinase coimmobilized with glucose-6-phosphate dehydrogenase, were immobilized by reactive poly(vinyl alcohol) carriers. The properties of the immobilized enzymes were investigated.

Enzymes, Immobilized↗

PubMed1979

[Reactive metabolites of xenobiotics : their role in the hepatotoxicity of drugs].

Certain drugs are transformed into reactive metabolites by cytochrome P-450, a hepatic microsomal enzyme. The reactive metabolites covalently bind to hepatocyte macromolecules, thus determining liver lesions. Induction of microsomial enzymes increases the formation of reactive metabolites and exaggerates hepatotoxicity of these drugs.

Acetaminophen↗

PubMed1991

Diagnosis of Lyme borreliosis by an enzyme immunoassay detecting immunoglobulin G reactive to purified Borrelia burgdorferi cell components.

An enzyme immunoassay (EIA) developed for the diagnosis of Lyme borreliosis was tested for its specificity and sensitivity in detecting IgG antibodies in patients at various stages of the disease. The EIA is based on a detergent extract of Borrelia burgdorferi which contains 12 proteins of defined molecular weights from Borrelia burgdorferi. The assay showed a specificity of 100% in control sera from 64 healthy individuals, using a cut-off optical density value of 0.13 (means +2- 3 SD). The sensitivity was 100% using sera from 22 Swedish patients with late stage Lyme borreliosis and 43% using sera from 30 patients with the initial stage of the disease. The reactivity of the sera against whole cell preparations, the outer surface proteins OspA and OspB, and the flagella of Borrelia burgdorferi was also tested and compared with the EIA. No cross-reactivity with treponemal antigens was observed when using the EIA.

Antibodies, Bacterial↗

PubMed1997

Roles of reactive oxygen species and antioxidant enzymes in murine daunomycin-induced nephropathy.

We evaluated the roles of reactive oxygen species and intrinsic antioxidant enzymes in the development of daunomycin (DM)-induced nephropathy in mice. A single dose of DM (20 mg/kg intravenously) induced proteinuria by day 7 and the nephrotic syndrome by day 14 in DM-sensitive strain (A/J) but not in DM-resistant strain (C57BL/6J) (B6). Renal cortical lipid peroxide levels in the A/J mice significantly increased at days 2, 4, and 7 after DM injection, whereas no increase was observed in the B6 mice. The resistance to DM in B6 mice was associated with higher activities in renal cortical superoxide dismutase and glutathione peroxidase. The administration of superoxide dismutase or of dimethylthiourea significantly suppressed the DM-induced proteinuria in the A/J mice. Four days of superoxide dismutase or dimethylthiourea administration suppressed the proteinuria. These findings suggested that murine DM-nephropathy appeared to be mediated by reactive oxygen species and that intrinsic antioxidant enzyme activities may play an important role in the susceptibility to DM-induced nephropathy in mice.

Albuminuria↗

PubMed1989

Oxygen radicals and antioxidant enzymes alter pulmonary vascular reactivity in the rat lung.

It has been postulated that changes in the availability of partially reduced O2 species, such as O2 radicals, could serve as a link between PO2 in the alveolus and pulmonary vascular tone (Herz 11: 127-141, 1986). To assess this hypothesis, the hemodynamic effects of acute changes in the balance between the production of O2 radicals and availability of antioxidant enzymes were studied in the isolated perfused rat lung. Intravascular generation of O2 radicals, by administration of xanthine-xanthine oxidase, decreased the pulmonary vascular pressor response to alveolar hypoxia (-55 +/- 5%) and angiotensin II (-58 +/- 10%, P less than 0.01 for each) in isolated perfused rat lungs without increasing the lung wet-to-dry weight ratio. Decreases in pulmonary vascular reactivity were inhibited by pretreatment of the lung with desferrioxamine or a mixture of catalase and superoxide dismutase. Catalase and superoxide dismutase preserved the hypoxic pressor response whether given in liposomes or in dissolved form. Superoxide dismutase administered free in solution, or combined with catalase in liposomes, increased the normoxic pulmonary arterial pressure and enhanced vascular reactivity to angiotensin II and hypoxia. Lungs treated with antioxidant enzymes in liposomes had 50% higher lung catalase levels than control lungs (P less than 0.05). These findings demonstrate that exogenous partially reduced O2 species can decrease pulmonary vascular reactivity and suggest that endogenous radicals, superoxide radical in particular, might be important in modulating pulmonary vascular tone.

Animals↗

PubMed1997

Use of human immunodeficiency virus (HIV) type 1 and 2 recombinant strip immunoblot assay to resolve enzyme immunoassay anti-HIV-2-repeatably reactive samples after anti-HIV-1/2 combination enzyme immunoassay screening.

BACKGROUND: With the implementation of combination human immunodeficiency virus types 1 and 2 (HIV-1/2) antibody enzyme immunoassay (EIA) in donor screening in 1992, the supplemental testing algorithm changed to require the use of a Food and Drug Administration (FDA)-licensed HIV-1 Western blot (WB) or immunofluorescence assay, as well as an FDA-licensed HIV-2 EIA. When HIV-2 EIA-reactive specimens are identified, further testing to confirm HIV-2 infection is recommended. Currently, a licensed HIV-2 supplemental assay is not available. STUDY DESIGN AND METHODS: The sensitivity of an HIV-1/2 recombinant strip immunoblot assay (SIA) for HIV-2 was determined on the basis of the analysis of 65 HIV-2-positive samples identified by the Centers for Disease Control and Prevention (CDC). Anti-HIV-1/2 combination EIA-repeatably reactive (RR) specimens from seven blood centers and their affiliated hospitals were tested in parallel by HIV-1 WB and HIV-2 EIA. Anti-HIV-2 EIA-RR specimens were further tested by HIV-1/2 SIA. Specimens interpreted as positive for HIV-2 or HIV-1/2 were referred to the CDC for final resolution of antibody status. RESULTS: Ninety-seven percent (63/65) of known HIV-2-positive samples tested positive for HIV-2 only or HIV-1/2 on the HIV-1/2 SIA. A total of 1048 anti-HIV-1/2 combination-EIA-RR specimens were evaluated. Sixty-nine percent (75/109) of the WB-positive specimens were HIV-2 EIA-RR, while only 9 percent (84/939) of WB-indeterminate or WB-negative specimens tested HIV-2 EIA-RR. The HIV-1/2 SIA resolved 91 percent of HIV-2 EIA-RR samples as negative. Four HIV-2 EIA-RR specimens (all HIV-1 WB-positive) were classified as positive for HIV-1 and HIV-2 in the HIV-1/2 SIA. Final interpretation of these specimens by CDC was that they were reactive for HIV-1 with cross-reactivity to HIV-2. CONCLUSION: No confirmed HIV-2-positive specimens were detected. The HIV-1/2 SIA is currently useful for resolving HIV-2 EIA-RR specimens.

AIDS Serodiagnosis↗

PubMed1984

An affinity label for the regulatory dithiol of ribulose-5-phosphate kinase from maize (Zea mays).

Ribulose-5-phosphate kinase from maize (Zea mays) can exist in either a reduced, active form or an oxidized, inactive form. Reduced ribulose-5-phosphate kinase is rapidly and irreversibly inactivated by the dichlorotriazine dye Reactive Red 1 (Procion Red MX-2B), but the irreversible inactivation of the oxidized form of ribulose-5-phosphate kinase occurs at only 0.05% of this rate. The rate of inactivation of the reduced enzyme by Reactive Red 1 (apparent bimolecular rate constant 10(4)M-1 X s-1 at pH 7.4 and 25 degrees C) is several orders of magnitude greater than previous estimates of the rates of dye-mediated inactivation of other enzymes. The dye-dependent inactivation of the reduced enzyme is inhibited by Hg2+ or p-mercuribenzoate (thiol reagents that reversibly inhibit ribulose-5-phosphate kinase activity), or by ATP and ADP, the nucleotide substrates of the enzyme. Hydrolysed Reactive Red 1, which does not inactivate the enzyme, is a reversible inhibitor of ribulose-5-phosphate kinase. This inhibition is competitive with respect to ATP (Ki approximately 0.5 mM). The dye appears to act as an affinity label for the ATP/ADP-binding site by preferentially arylating a thiol residue generated during the reductive activation of the enzyme that is achieved by dithiothreitol or thioredoxin in vitro or during illumination of leaves.

Adenine Nucleotides↗

PubMed2001

Effect of the angiotensin-converting enzyme inhibitor imidapril on reactive hyperemia in patients with essential hypertension: relationship between treatment periods and resistance artery endothelial function.

OBJECTIVES: The purpose of this study was to evaluate the effects of the angiotensin-converting enzyme (ACE) inhibitor imidapril and the calcium antagonist amlodipine on endothelial function before and after 2, 4, 8, 12, 24 and 48 weeks of treatment. BACKGROUND: There are limited data on whether and how long endothelial function is improved after initiation of ACE inhibitor treatment and how the grade of endothelial function further progresses after improvement of endothelial dysfunction in patients with essential hypertension. METHODS: The forearm blood flow (FBF) was measured in 25 patients with essential hypertension and in 25 normotensive subjects by using strain-gauge plethysmography during reactive hyperemia (RH) (280 mm Hg for 5 min) and after sublingual administration of nitroglycerin (NTG, 0.3 mg). RESULTS: The FBF of patients with essential hypertension during RH was significantly less than that of normotensive subjects. The increase in FBF after sublingual NTG was similar in both groups. Both imidapril (n = 13) and amlodipine (n = 12) significantly reduced systolic blood pressure and diastolic after eight weeks of treatment from the pretreatment values. Forearm vascular resistance was significantly decreased after two weeks of treatment. Imidapril significantly augmented RH after 12 weeks of treatment from the pretreatment values (31.6 +/- 5.7 to 38.2 +/- 6.0 m/min per 100 ml tissue, p < 0.05), whereas amlodipine did not alter RH for each treatment period. The ability of imidapril to improve RH was maintained throughout the 48-week treatment period. There was no significant difference in RH at 12, 24 and 48 weeks. The increase in FBF after sublingual administration of NTG was similar in all treatment periods for the two groups. The infusion of NG-monomethyl-L-arginine, a nitric oxide (NO) synthase inhibitor, abolished the enhancement of RH in hypertensive patients treated with imidapril. CONCLUSIONS: These findings suggest that the ACE inhibitor imidapril augments RH after 12 weeks of treatment in patients with essential hypertension and that this ACE inhibitor-induced augmentation of RH may be due to an increase in NO.

Aged↗

PubMed2002

Exploring the active site of amine:pyruvate aminotransferase on the basis of the substrate structure-reactivity relationship: how the enzyme controls substrate specificity and stereoselectivity.

An active site model of the amine:pyruvate aminotransferase (APA) from Vibrio fluvialis JS17 was constructed on the basis of the relationship between substrate structure and reactivity. Due to the broad substrate specificity of the APA, various amino donors (chiral and achiral amine, amino acid, and amino acid derivative) and amino acceptors (keto acid, keto ester, aldehyde, and ketone) were used to explore the active site structure. The result suggested a two-binding site model consisting of two pockets, one large (L) and the other small (S). The difference in the size of each binding pocket and strong repulsion for a carboxylate in the S pocket were key determinants to control its substrate specificity and stereoselectivity. The L pocket showed dual recognition mode for both hydrophobic and carboxyl groups as observed in the side-chain pockets of aspartate aminotransferase and aromatic aminotransferase. Comparison of the model with those of other aminotransferases revealed that the L and S pockets corresponded to carboxylate trap and side-chain pocket, respectively. The active site model successfully explains the observed substrate specificity as well as the stereoselectivity of the APA.

Binding Sites↗

PubMed1992

Identification of the histidine residue in Escherichia coli isocitrate lyase that reacts with diethylpyrocarbonate.

Escherichia coli isocitrate lyase was inactivated by diethylpyrocarbonate in a pseudo-first-order process. The enzyme was completely inactivated by modification of a single histidine residue, but slower modification of further residues also occurred. The substrate, isocitrate, and products, glyoxylate and succinate, protected against inactivation by diethylpyrocarbonate but this was not simply due to binding at the active site. Treatment of the inactivated enzyme with hydroxylamine led to only partial recovery of activity. Diethylpyrocarbonate also reacted with sulphydryl groups in isocitrate lyase, as judged by titrations with Nbs2, but this reaction was not responsible for the failure of hydroxylamine to reactivate the enzyme fully. The reactivity of isocitrate lyase to diethylpyrocarbonate declined with pH, following a titration curve for a group of pKa 6.1. Isolation and sequencing of ethoxyformylated peptides showed that the major site of modification by diethylpyrocarbonate was histidine residue 306.

Amino Acid Sequence↗

PubMed1996

Involvement of a disulfide bridge in catalytic activity of camel lens xi-crystallin.

Chemical modification studies were performed to elucidate the role of cysteine residues in the catalytic activity of camel lens xi-crystallin. 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) titration of the camel lens xi-crystallin revealed that it contained 3 SH-groups and a disulfide bridge per subunit. One of the three SH-groups was readily accessible, whereas the other two were buried. Inactivation of xi-crystallin by DTNB was caused by a modification of one cysteine residue per subunit. The resulting DTNB-modified enzyme was reactivated by dithiothreitol (DTT) or KCN. The inactivation was partially protected by NADPH, whereas 9,10-phenanthrenequinone (PQ) enhanced the modification of the enzyme. These results indicate that the SH- group being modified is located at/near the NADPH binding site which is not essential for catalysis. Incubation of the enzyme with DTT led to a substantial loss of the enzyme activity. However, DTT inhibition was prevented completely by preincubation of enzyme with PQ but not by NADPH indicating that an essential disulfide-bridge is present at the substrate binding site of xi-crystallin.

Animals↗

PubMed1986

The phosphate group of 3-phosphoglycerate accounts for conformational changes occurring on binding to 3-phosphoglycerate kinase. Enzyme inhibition and thiol reactivity studies.

Steady-state kinetic study of the inhibition of 3-phosphoglycerate kinase reaction by the substrate analogues D-glycerol 3-phosphate, 2-phosphoglycolate, tartronate and malonate revealed competition with respect to 3-phosphoglycerate. D-Glycerate had no detectable inhibitory effect. The data indicate that (a) the phosphate of 3-phosphoglycerate plays an essential role in the formation of its complex with the enzyme and, taking into account the relatively strong binding of 3-phosphoglycerate, (b) the two charged groups of the substrate might cause a synergic interaction with the protein. The carboxyl-lacking D-glycerol 3-phosphate is a non-competitive inhibitor with respect to MgATP, while all the investigated carboxyl-containing inhibitors compete for MgATP binding. The inhibitory analogues of 3-phosphoglycerate reduce the reactivity of both the two fast-reacting and the five slow-reacting thiol groups of the enzyme molecule. In the case of the fast-reacting thiols the effect is specifically associated with the presence of a ligand's phosphate group. Similarly mainly the phosphate-containing nucleotides and analogues slow down significantly the reaction rate of the fast-reacting thiols, while adenosine is less effective and the competitive inhibitor adenine has no effect at all. MgADP has an especially dramatic effect as compared to MgATP, in line with the known X-ray structural data. The fast-reacting thiols are of particular interest, since their reactivity is possibly controlled by ligand-induced conformational changes. This is shown by the similar ligand protection against alkylation irrespective of the reagent's electrostatic charge (iodoacetamide or iodoacetate) and also by the similar substrate-binding properties of carboxamidomethylated and the unmodified enzyme.

Animals↗

PubMed1993

A chaperone-mimetic effect of serum albumin on rhodanese.

Reactivation of denatured rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1) was found to be aided by the presence of serum albumin. Both the rate and the extent of reactivation of the urea-denatured enzyme were optimal at low rhodanese and moderate serum albumin concentrations. Similarly, stabilization of the sulfurtransferase activity of rhodanese that had been partially unfolded at 40 degrees C was aided by the presence of serum albumin. All the observations are in accord with a model in which enzyme that has been partially refolded from the urea-denatured state or partially unfolded thermally interacts directly with serum albumin in a way that prevents rhodanese self-association. Serum albumin thus acts as a molecular chaperone in these systems.

Animals↗