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M Saxena

Publications and source records attributed to M Saxena.

At least 19 recordsLinked to original sources
PubMed1992

A subgroup of class alpha glutathione S-transferases. Cloning of cDNA for mouse lung glutathione S-transferase GST 5.7.

A full-length cDNA clone encoding the previously purified mouse glutathione S-transferase GST 5.7 [(1991), Biochem. J. 278, 793-799] has been isolated from a mouse lung cDNA library in lambda gt11. Sequencing of the clone revealed the presence of microheterogeneity in GST 5.7. Comparison of the deduced protein sequence with other glutathione S-transferases, together with previous information available on GST 5.7, indicates that the enzyme belongs to a novel subgroup within the alpha class of glutathione S-transferases. Members of the subgroup, which also include the rat GST 8-8 and perhaps chicken GST CL3, show high sequence homology with each other, but only moderate similarity to other alpha class enzymes. They share a substrate specificity profile that resembles pi-class enzymes, and are active in the conjugation of lipid peroxidation products.

Amino Acid Sequence↗
PubMed1992

Gender related differences in the expression and characteristics of glutathione S-transferases of human colon.

In the present study, the expression of glutathione S-transferase (GST) isozymes was compared in human male and female colon tissues. GST isozymes were purified and quantified in five male and five female colon tissue samples. Noticeable differences were observed in the isoelectric focusing profiles (IEF) of the GSTs, from male and female colon tissues. Both male and female colon tissues had three common GST peaks with pI values of 9.2, 6.7 and 4.8. An additional GST peak with a pI value of 6.2 found in all females was not found in males. Based on kinetic, immunological and structural properties, these isozymes were classified into alpha (pI 9.2), mu (pI 6.7 and 6.2) and pi (pI 4.8) classes. Activity of the alpha-class GST in male colon was approx. 2-fold higher than the corresponding isozyme in female colon. The pi-class GST 4.8 was the most predominant GST in both the sexes and its activity with CDNB as substrate was more abundant (about 1.6-fold) in female colon as compared to that in male colon. Significant differences were seen in substrate specificities between male and female colon GST 4.8. Sex related differences were also observed in the inhibition kinetics of GST pi from male and female colon in the presence of hematin. In addition, GST pi isolated from female colon was more thermostable as compared to the corresponding male isozyme. The thermostability of purified GST pi isozyme from males or females was not affected by incubation of the enzyme with either estrogen, testosterone or progesterone.

Amino Acid Sequence↗
PubMed1992

Glutathione S-transferases of mouse liver: sex-related differences in the expression of various isozymes.

Sex-related differences in the expression of glutathione S-transferase (GST) isozymes of mouse liver have been described. There were no apparent qualitative differences in the isoelectric focusing profiles of the GST isozymes from male and female mouse liver. Both male and female mice have at least four GST isozymes in their liver with pI values of 9.8, 8.7, 6.4 and 5.7. Kinetic, immunological, and structural properties including the N-terminal region amino acid sequences of these isozymes have been determined and they have been classified into alpha, mu, and pi classes. The most cationic isozyme (pI 9.8) belongs to the alpha class and is comparatively more abundant in female liver. The isozyme having pI 8.7 belongs to the pi class and is more abundant in male liver. The mu class GST pI 6.4 as well as the isozyme having pI 5.7 which corresponded to the a class isozyme GST 8-8 of rat liver were more abundant (about 1.5-fold) in male mouse liver as compared to the female. Interestingly, present studies reveal sex-related differences in the heat stabilities of the alpha and pi class GSTs of mouse liver. The alpha class GST pI (9.8) isolated from female mouse liver was more thermostable as compared to the corresponding enzyme from male mouse liver. On the contrary, the pi class GST (pI 8.7) from male mouse was more thermostable as compared to the corresponding enzyme from the female mouse.

Amino Acid Sequence↗
PubMed1992

Identification of an anion-transport ATPase that catalyzes glutathione conjugate-dependent ATP hydrolysis in canalicular plasma membranes from normal rats and rats with conjugated hyperbilirubinemia (GY mutant).

Rat liver canalicular plasma membranes were found to contain a 37-kDa protein that is immunologically cross-reactive with the dinitrophenyl glutathione-stimulated ATPase previously identified in human tissues. The protein, which was partially purified by affinity chromatography, exhibited ATPase activity dependent on dinitrophenyl glutathione, bilirubin ditaurate, and other dianionic compounds. The localization of this protein in the canalicular membrane and its measured enzymatic activity indicate that it is involved in the transport of glutathione derivatives and other dianionic organic compounds. A rat mutant in which the above transport activities are impaired contained the protein in amounts similar to those in a normal control.

Adenosine Triphosphatases↗
PubMed1992

Piperine, a plant alkaloid of the piper species, enhances the bioavailability of aflatoxin B1 in rat tissues.

Piperine is known to modify the biotransformation of drugs. The effect of piperine on the metabolic activation and distribution of [3H]-aflatoxin B1 (AFB1) in rats has been described. Piperine markedly inhibited liver microsome-catalysed [3H]AFB1 binding to calf thymus DNA in vitro, in a dose dependent manner. Rats pretreated with piperine accumulated considerable [3H]AFB1 radioactivity in plasma and in the tissues examined as compared to the controls. However, piperine had no influence on hepatic [3H]AFB1-DNA binding in vivo, which could possibly be due to the null effect of piperine on liver cytosolic glutathione (GSH) 5-transferase activity. Piperine-treated rat liver microsomes demonstrated a tendency to enhance [3H]AFB1 binding to calf thymus DNA in vivo. The effect of piperine on AFB1 metabolism thus closely resembles the mode of action of SKF 525-A on biotransformation of foreign compounds.

Aflatoxin B1↗
PubMed1992

Dinitrophenyl S-glutathione ATPase purified from human muscle catalyzes ATP hydrolysis in the presence of leukotrienes.

Dinitrophenyl S-glutathione (Dnp-SG) ATPase has been purified from human muscle to apparent homogeneity using Dnp-SG affinity chromatography and immunoaffinity chromatography using antibodies raised against human erythrocyte Dnp-SG ATPase. The enzyme purified from human muscle showed a subunit M(r) value of about 38 kDa in denaturing gels. The M(r) value of the native enzyme as determined by Sephadex G-200 gel filtration was found to be about 80 kDa, which indicates that it is a dimer. The N-terminus of the enzyme was blocked. Its immunological and kinetic properties were similar to Dnp-SG ATPase of human erythrocytes. Besides catalyzing the ATP hydrolysis in the presence of Dnp-SG, the muscle enzyme also catalyzed ATP hydrolysis in the presence of various leukotrienes, namely LTC4.LTD4, LTE4, and N-acetyl LTE4. The specific activity of the enzyme toward LTC4 was relatively higher than other GSH-xenobiotic conjugates. The muscle enzyme exhibits a low Km value for all leukotrienes as compared to Dnp-SG, indicating high affinity of the enzyme for leukotrienes as activators. The enzyme also catalyzed ATP hydrolysis in the presence of GSH conjugates of endogenously generated fatty acid epoxides. Our results might suggest that Dnp-SG ATPase is involved in the transport of GSH conjugates, leukotrienes, and other organic anions in muscle, erythrocytes, liver, and probably other tissues.

Adenosine Triphosphatases↗
PubMed1992

Glutathione S-transferases of human lung: characterization and evaluation of the protective role of the alpha-class isozymes against lipid peroxidation.

Glutathione S-transferase (GST) isozymes of human lung have been purified, characterized, quantitated, and, based on their structural and immunological profiles, identified with their respective classes. The tau-, mu-, and alpha-class GSTs represented 94, 3, and 3% activities of total human lung GSTs toward CDNB, respectively, and 60, 10, and 30% of total GST protein, respectively. Both the mu- and the alpha-class GSTs of human lung exhibited heterogeneity. The two mu-class GSTs of human lung had pI values of 6.5 and 6.25 and were differentially expressed in humans. Significant differences were seen between the kinetic properties of these two isozymes and also between the lung and liver mu-class GSTs. The alpha-class GST isozymes of lung resolved into three peaks during isoelectric focusing corresponding to pI values of 9.2, 8.95, and 8.8. All three alpha-class GSTs isozymes had blocked N-termini and were immunologically similar to human liver alpha-class GSTs. Peptide fingerprints generated by SV-8 protease digestion and CNBr cleavage indicated minor structural differences between the liver and the lung alpha-class GSTs. The three alpha-class GSTs of lung expressed glutathione peroxidase activities toward the hydroperoxides of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, with Km values in the range of 22 to 87 microM and Vmax values in the range of 67-120 mol/mol/min, indicating the involvement of the alpha-class GSTs in the protection mechanisms against peroxidation. All three classes of lung GSTs expressed activities toward leukotriene A4 methyl ester and epoxy stearic acid but the mu-class GSTs had relatively higher activities toward these substrates.

Blotting, Western↗
PubMed1992

A specific, sensitive, and rapid method for the determination of glutathione and its application in ocular tissues.

A method for specific determination of glutathione (GSH) is described. This method utilizes the enzymatic conjugation of GSH to 1-chloro-2,4-dinitrobenzene through reaction catalyzed by glutathione S-transferase. The recovery of GSH as determined by this method is comparable to that in currently used methods. The method is specific for GSH determination. Other sulfhydryl (-SH) compounds including the protein -SH or beta-mercaptoethanol, which are often included in tissue homogenates, do not interfere with GSH determination. Acid extraction of the tissue is not required in this method and comparatively smaller amounts of tissue samples (as little as 20 microliters of a 10% w/v tissue homogenate) are needed for the analyses. The method when applied for GSH determination in ocular tissues yielded results in agreement with the reported values in literature. Evidence for the sensitivity, accuracy, and convenience of the method is provided by analysing the sample containing GSH in the range of 1-200 nmol by this method.

Animals↗
PubMed1991

Purification and characterization of glutathione S-transferases from rat pancreas.

Glutathione S-transferases (GSTs) of rat pancreas have been characterized and their interrelationship with fatty acid ethyl ester synthase (FAEES) has been studied. Seven GST isozymes with pI values of 9.2, 8.15, 7.8, 7.0, 6.3, 5.9 and 5.4 have been isolated and designated as rat pancreas GST suffixed by their pI values. Structural, immunological and kinetic properties of these isozymes indicated that GST 9.2 belonged to the alpha class, GST 7.8, 7.0, 6.3 and 5.9 belonged to the mu class, whereas GST 8.15 and 5.4 belong to pi class. The N-terminal sequences and pI values of the mu class isozymes suggested that rat GST subunits 3, 4 and 6 may be expressed in pancreas. N-Terminal sequences of both the pi class isozymes, GST 8.15 and 5.4, were similar to that of GST-P, but there were significant differences in the substrate specificities of these two enzymes. Results of peptide finger print studies also indicated minor structural differences between these two isozymes. None of the GST isozymes of rat pancreas expressed FAEES activity. Rat pancreas had a significant amount of FAEES activity, but it segregated independently during the purification of GST indicating that these two activities are expressed by different proteins and are not related as suggested previously.

Acyltransferases↗
PubMed1991

Characterization of a novel glutathione S-transferase isoenzyme from mouse lung and liver having structural similarity to rat glutathione S-transferase 8-8.

In mouse lung, glutathione S-transferase (GST, EC 2.5.1.18) isoenzymes belonging to the three major known classes, Alpha, Mu and Pi, have been previously characterized, along with an isoenzyme (pI 5.7) that could not be identified with the Alpha, Mu or Pi classes of GSTs. In the present studies we have demonstrated that this isoenzyme is also expressed in liver. Its structural, kinetic, and immunological properties have been determined and compared with those of the three classes of GSTs. GST 5.7 has a subunit molecular mass of 23 kDa, which is intermediate between that of the previously characterized Alpha (25 kDa) and Pi (22.5 kDa) class GST subunits of mouse lung. Comparison of peptide maps of GST 5.7 with those representative of Alpha, Mu and Pi class GST isoenzymes of mouse lung showed that it had a distinct peptide fragmentation pattern. Kinetic and immunological properties of GST 5.7 were also distinct from other mouse GST isoenzymes belonging to the Alpha, Mu or Pi classes. N-Terminal amino-acid-sequence analysis of a 6 kDa fragment generated by CNBr digestion of mouse lung GST 5.7 revealed a 15-residue sequence that was distinct from sequences of known Alpha, Mu and Pi class mouse GSTs. The sequence, however, matched with the sequence of rat GST 8-8 between amino acid residues 106 and 120 with a 73% identity. The 6 kDa and 12 kDa fragments generated by CNBr digestion of mouse liver GST 5.7 also gave sequences which matched with those of rat GST 8-8 between positions 106 and 120 and 167 and 186, with a high degree of identity. These studies suggest that mouse GST 5.7 structurally corresponds to rat GST 8-8 and belongs to the Alpha class.

Amino Acid Sequence↗
PubMed1991

Contribution of silver ion resistance to the pathogenicity of Pseudomonas aeruginosa with special reference to burn wound sepsis.

The virulence of a silver-ion-resistant (AgR) clinical isolate of Pseudomonas aeruginosa and its silver-sensitive mutant (AgS) was compared in the murine burn-wound sepsis model. The AgR strain showed significantly higher colonization of burned skin vis-a-vis the AgS strain. The altered pathogenicity may in part be due to the decrease in capsular content and cell surface hydrophobicity, accompanying the loss of silver ion resistance. The AgR and AgS strains, however, did not exhibit quantitatively significant differences in the production of extracellular hemolysins and proteinases.

Animals↗
PubMed1991

Epoxidation of aflatoxin B1 by Aspergillus flavus microsomes in vitro: interaction with DNA and formation of aflatoxin B1-glutathione conjugate.

Metabolism of aflatoxin B1 (AFB1) by subcellular preparations of Aspergillus flavus is least understood. The results reported here have demonstrated for the first time the epoxidation of AFB1 and subsequent conjugation with glutathione (GSH). Microsomes prepared from toxigenic mycelia catalysed [3H]AFB1 to calf thymus DNA to a greater extent (approximately 2-fold) as compared to that of non-toxigenic. The binding of [3H]AFB1 to exogenous and A. flavus nuclear DNA catalyzed by A. flavus microsomes was found to be comparable with that of mammalian extrahepatic tissue such as lung. Addition of phenobarbitone to the growing cultures resulted in 1.5-fold increase in [3H]AFB1-DNA binding mediated by microsomes prepared from either of the two strains. Tolnaftate, an inhibitor of aflatoxin synthesis enhanced the epoxidation rate in a dose-related manner. The binding of [3H]AFB1 to DNA catalyzed by A. flavus microsomes was significantly reduced (50% of control) upon addition of hamster liver cytosol, thereby substantiating the formation of the carcinogen adduct with DNA as reported in mammalian tissues. The metabolite formed by subcellular preparation of A. flavus was found to be AFB1-GSH having Rf value (6.5) similar to that obtained for mammalian liver preparations.

Aflatoxin B1↗
PubMed1991

Amoxicillin-clavulanic acid for treating drug-resistant Mycobacterium tuberculosis.

This report describes two patients with multidrug resistant tuberculosis who were successfully treated with the addition of amoxicillin-clavulanic acid to second-line drugs. Mycobacterium tuberculosis possesses a beta-lactamase contributing to its resistance to beta-lactam antibiotics. The combination of clavulanic acid, a beta-lactamase inhibitor, and amoxicillin has been shown bactericidal for M tuberculosis in vitro. These data suggest that resistant tuberculosis may warrant a trial of treatment including amoxicillin-clavulanic acid.

Adult↗
PubMed1990

In vitro growth of urinary Escherichia coli related to siderophore production.

Thirty seven strains of Escherichia coli isolated from the urine of patients with acute symptomatic urinary tract infection were examined for siderophore production: hydroxamate (aerobactin) and phenolate (enterochelin). All the strains were found to produce varying amounts of enterochelin. With the chemical assay, 24.3% strains were aerobactin producers, while 43.2% were positive in the bio-assay. All the aerobactin producers carried the aerobactin receptor on their surface. Attempts to correlate siderophore production with growth in minimal and iron-depleted medium showed that there was a positive quantitative correlation between enterochelin production and growth of organisms under iron depletion. Aerobactin production failed to give an additional advantage of growth to strains producing enterochelin.

Bacterial Outer Membrane Proteins↗
PubMed1990

Synthesis, biological evaluation, and quantitative structure-activity relationship analysis of [beta-(Aroylamino)ethyl]piperazines and -piperidines and [2-[(Arylamino)carbonyl]ethyl]piperazines, -pyrazinopyridoindoles, and -pyrazinoisoquinolines. A new class of potent H1 antagonists.

Some [beta-(Aroylamino)ethyl]piperazines and -piperidines and [2-[(Arylamino)carbonyl]ethyl]piperazines, -piperidines, -pyrazinopyridoindoles, and -pyrazinoisoquinolines have been synthesized and their H1-antagonistic activity studied in isolated guinea pig ileum. Quantitative structure-activity relationship analysis indicates that the hydrophobicity of the side chain of these compounds plays a major role in their activity while steric and electronic factors are of secondary importance. All these compounds act on a common receptor and appear to interact similarly with the receptor.

Amines↗