[Structure of the "active zone" of nucleoside diphosphate-glucide transferases. Definition of an "acylophilic" site in uridine diphosphate glucose-glycogen transferase].
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Animals↗
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[Structure of uridine P-P-glucose transferases: interaction of glucose-6-phosphate and salicylic acid in uridine P-P-glucose-glycogen transferase of rabbit muscle].
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Animals↗
Multiplicity and specificity of UDP-glucuronyl transferase. 3. UDP-glucuronyl transferase and -glucuronidase activities assayed with different substrates in inherited and acquired human liver diseases.
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Alcoholism↗
Chloroform-induced alteration of glutathione S-transferase activity.
The effect of chloroform treatment on the hepatic glutathione S-transferases was studied in phenobarbital-treated rats. The apparent isozymic composition of glutathione S-transferases in hepatic cytosol was changed after chloroform treatment. Glutathione S-transferases AA, A, B, C, and D + E were observed in hepatic cytosol from untreated rats; in contrast, the catalytic activity associated with basic glutathione S-transferases, such as AA, A, B, and C, decreased with time after chloroform treatment. Glutathione S-transferase B was not detectable 2 hr after chloroform treatment, and glutathione S-transferases AA and C were scarcely detectable after 5 hr. Twenty-four hours after chloroform treatment, glutathione S-transferases A and C were clearly detectable as was D + E and a small amount of B. Hepatic cytosolic glutathione S-transferase activity was decreased by chloroform treatment, and reached a minimum at 5 hr after treatment. Corresponding to the decrease of hepatic cytosol glutathione S-transferase activity, serum glutathione S-transferase activity was elevated maximally 5 hr after chloroform treatment and returned to almost normal by 24 hr. Treatment of rats with SKF 525-A or cysteine inhibited the chloroform-induced elevation of serum glutathione S-transferase activity. The chromatographic properties of the glutathione S-transferases present in serum were similar to glutathione S-transferase D + E. Furthermore, after incubation of partially purified cytosolic glutathione S-transferases with chloroform in the presence of hepatic microsomes and NADPH, only transferase D + E was detected. The addition of bilirubin to partially purified cytosolic glutathione S-transferase decreased the basic character of glutathione S-transferases B and C. In conclusion, chloroform caused a release of hepatic cytosolic glutathione S-transferases into serum. Both the active metabolite of chloroform, which was produced by the microsomal cytochrome P-450 system, and bilirubin, which was increased by chloroform treatment, played roles in altering the properties of the glutathione S-transferases.
Animals↗
Interrelationship between anionic and cationic forms of glutathione S-transferases of human liver.
Human liver glutathione S-transferases (GSH S-transferases) were fractionated into cationic and anionic proteins. During fractionation with (NH4)2SO4 the anionic GSH S-transferases are concentrated in the 65%-saturated-(NH4)2SO4 fraction, whereas the cationic GSH S-transferases separate in the 80%-saturated-(NH4)2SO4 fraction. From the 65%-saturated-(NH4)2SO4 fraction two new anionic GSH S-transferases, omega and psi, were purified to homogeneity by using ion-exchange chromatography on DEAE-cellulose, Sephadex G-200 gel filtration, affinity chromatography on GSH bound to epoxy-activated Sepharose and isoelectric focusing. By a similar procedure, cationic GSH S-transferases were purified from the 80%-saturated-(NH4)2SO4 fraction. Isoelectric points of GSH S-transferases omega and psi are 4.6 and 5.4 respectively. GSH S-transferase omega is the major anionic GSH S-transferase of human liver, whereas GSH S-transferase psi is present only in traces. The subunit mol.wt. of GSH S-transferase omega is about 22500, whereas that of cationic GSH S-transferases is about 24500. Kinetic and structural properties as well as the amino acid composition of GSH S-transferase omega are described. The antibodies raised against cationic GSH S-transferases cross-react with GSH S-transferase omega. There are significant differences between the catalytic properties of GSH S-transferase omega and the cationic GSH S-transferases. GSH peroxidase II activity is displayed by all five cationic GSH S-transferases, whereas both anionic GSH S-transferases do not display this activity.
Amino Acids↗
Isoelectric focusing of glutathione S-transferases from rat liver and kidney.
The glutathione S-transferases that were purified to homogeneity from liver cytosol have overlapping but distinct substrate specificities and different isoelectric points. This report explores the possibility of using preparative electrofocusing to compare the composition of the transferases in liver and kidney cytosol. Hepatic cytosol from adult male Sprague-Dawley rats was resolved by isoelectric focusing on Sephadex columns into five peaks of transferase activity, each with characteristic substrate specificity. The first four peaks of transferase activity (in order of decreasing basicity) are identified as transferases AA, B, A and C respectively, on the basis of substrate specificity, but the fifth peak (pI6.6) does not correspond to a previously described transferase. Isoelectric focusing of renal cytosol resolves only three major peaks of transferase activity, each with narrow substrate specificity. In the kidney, peak 1 (pI9.0) has most of the activity toward 1-chloro-2,4-dinitrobenzene, peak 2 (pI8.5) toward p-nitrobenzyl chloride, and peak 3 (pI7.0) toward trans-4-phenylbut-3-en-2-one. Renal transferase peak 1 (pI9.0) appears to correspond to transferase B on the basis of pI, substrate specificity and antigenicity. Kidney transferase peaks 2 (pI8.5) and 3 (pI7.0) do not correspond to previously described glutathione S-transferases, although kidney transferase peak 3 is similar to the transferase peak 5 from focused hepatic cytosol. Transferases A and C were not found in kidney cytosol, and transferase AA was detected in only one out of six replicates. Thus it is important to recognize the contribution of individual transferases to total transferase activity in that each transferase may be regulated independently.
Animals↗
Mouse liver glutathione S-transferases. Biochemical and immunological characterization.
Three major forms of cytosolic glutathione S-transferase (designated F1, F2, and F3 transferases according to increasing isoelectric points) were purified to homogeneity from liver of DBA/2J mice, primarily by CM-cellulose and hydroxylapatite chromatography. The purified enzymes were shown to have specific activities of 104, 281, and 143 units/mg, respectively, when assayed with 1 mM each of 1-chloro-2,4-dinitrobenzene and reduced glutathione. Antisera against these three forms of mouse transferase were raised separately in rabbits. F1 and F2 transferases showed complete immunological identity either by double immunodiffusion or enzyme immunoinactivation tests. No cross-reactivity was observed between the antisera to F1 (or F2) transferase an F3 transferase or between the antisera to F3 transferase and F1 (or F2) transferase. F1 and F2 transferases were shown to be homodimers with an identical molecular weight of 44,000 +/- 1,000, whereas F3 transferase has a dimeric molecular weight of 51,000 +/- 2,000. The amino acid composition and tryptic peptide map of F1 transferase are similar to those of F2 transferase, but are distinct from those of F3 transferase. In addition to these major forms, a minor form of mouse transferase (F4) with a high isoelectric point (greater than 9.5) was shown to be a mixture of interconvertible isomers of F2 and F3 transferase. Different forms of mouse transferase were studied extensively with respect to their biochemical properties, including Michaelis constants, substrate specificity, thermal stability, and fluorometric ligand binding. The results of this study suggest great species variations regarding the multiple forms as well as the substrate specificity of this family of enzymes.
Amino Acids↗
Identification and expression of a novel class of glutathione-S-transferase from amphioxus Branchiostoma belcheri with implications to the origin of vertebrate liver.
Glutathione-S-transferases have been identified in all the living species examined so far, yet little is known to date about them in amphioxus, a model organism for insights into the origin and evolution of vertebrates. We have isolated a cDNA encoding an amphioxus (Branchiostoma belcheri) glutathione-S-transferase with a predicted molecular mass of approximately 26 kDa, from the gut cDNA library. The glutathione-S-transferase had 43.7-51.8% identity to most glutathione-S-transferases identified from aquatic organisms including fish and green alga, but it was much less identical (<27%) to other cytosolic glutathione-S-transferase classes. The phylogenetic analysis revealed that the glutathione-S-transferase was grouped together with most piscine and algal glutathione-S-transferases, separating from other cytosolic glutathione-S-transferase classes. Moreover, the glutathione-S-transferase had an exon-intron organization typical of zebrafish putative GST, red sea bream GSTR1 and plaice GSTA1 genes. The recombinant glutathione-S-transferase has been successfully expressed and purified, which showed a relatively high catalytic activity (3.37+/-0.1 unit/mg) toward 1-chloro-2, 4-dinitrobenzene and a moderate activity toward ethacrynic acid (0.41+/-0.01 unit/mg), although it had no detectable activity toward 1, 2-dichloro-4-nitrobenzene, 4-hydroxynonenal, 4-nitrobenzyl chloride and cumene hydroperoxide. In addition, we have revealed a tissue-specific expression pattern of the glutathione-S-transferase gene in B. belcheri, with the most abundant expression in the hepatic caecum. All these indicate that the amphioxus glutathione-S-transferase belongs to a novel rho-class of glutathione-S-transferases with a tissue-specific expression pattern. The relation between the glutathione-S-transferase expression in amphioxus hepatic caecum and the origin of vertebrate liver is also discussed.
Amino Acid Sequence↗
Glutathione S-transferases in human ovarian follicular fluid.
OBJECTIVE: To study the levels of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 in human preovulatory ovarian follicular fluid (FF) and pooled granulosa and cumulus cells. DESIGN: The relation of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 with P and 17 beta-E2 concentrations were studied. SETTING: The Department of Obstetrics and Gynecology, the Department of Gastroenterology, and the Laboratory of Endocrinology and Reproduction of the University Hospital Nijmegen in Nijmegen, the Netherlands. PATIENT(S): Infertile women participating in an IVF program. RESULT(S): Detectable amounts of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 were found in ovarian FF and pooled cumulus and granulosa cells. Concentrations of glutathione S-transferase Alpha 1-1 were always much higher than those of glutathione S-transferase Pi 1-1. Both ovarian FF concentrations of glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 did not correlate with ovarian FF concentrations of 17 beta-E2 and P. CONCLUSION(S): The high FF concentrations of glutathione S-transferase Pi 1-1 and especially of glutathione S-transferase Alpha 1-1 suggest that these enzymes may play an important role in the detoxification processes in the follicles. The lack of correlation between follicular P and 17 beta-E2 and glutathione S-transferase Alpha 1-1 and glutathione S-transferase Pi 1-1 indicates that both enzymes presumably are not present as a result of the high steroid levels.
Estradiol↗
Purification and characterization of glutathione S-transferases P, S and N. Isolation from rat liver of Yb1 Yn protein, the existence of which was predicted by subunit hybridization in vitro.
The glutathione S-transferases are dimeric proteins and comprise subunits of Mr 25 500 (Ya), 26 500 (Yn), 27 000 (Yb1 and Yb2) and 28 500 (Yc). Enzymes containing Ya and/or Yc subunits have been isolated as have forms containing binary combinations of Yn, Yb1 and Yb2 subunits. To date only one enzyme, transferase S, has been described that is a YbYn heterodimer [Hayes & Chalmers (1983) Biochem. J. 215, 581-588]; the identity of the Yb monomer found in transferase S has not been reported previously. The identification and isolation of a YnYn dimer (transferase N) from rat testis is now described. This has enabled structural and functional comparisons to be made between Yb1, Yb2 and Yn monomers. Reversible dissociation experiments between the YnYn and Yb1Yb1 homodimers and between the YnYn and Yb2Yb2 homodimers demonstrated that Yn monomers can hybridize with both Yb1 and Yb2 monomers. Reversible dissociation of transferases N and C (Yb1Yb2) showed that both Yb1 and Yb2 monomers can hybridize with Yn monomers under competitive conditions. The hydridization data suggest that transferase S represents the Yb2Yn subunit combination. A knowledge of the elution position from chromatofocusing columns of the Yb1Yn hybrid that was formed in vitro enabled a purification scheme to be devised for an enzyme from rat liver (transferase P) believed to consist of Yb1Yn subunits. A comparison of the chromatographic behaviour of the YnYn, Yb1Yb1 and Yb2Yb2 dimers on chromatofocusing and hydroxyapatite columns with the behaviour of transferases P and S on the same matrices suggests these two enzymes may be identified as the Yb1Yn and Yb2Yn dimers respectively. The catalytic activities and the inhibitory effects of non-substrate ligands on transferases P and S are significantly different and again suggest they comprise Yb1 and Yn subunits and Yb2 and Yn subunits respectively; transferase P exhibits a 6-fold higher specific activity for 1,2-dichloro-4-nitrobenzene than does transferase S, whereas, conversely, transferase S possesses a 9-fold higher specific activity for trans-4-phenylbut-3-en-2-one than does transferase P. The quaternary structure of transferases P and S was verified by using peptide mapping and 'Western blotting' techniques.
Animals↗
Glutathione-S-transferase P1-1 protects aberrant crypt foci from apoptosis induced by deoxycholic acid.
BACKGROUND & AIMS: Aberrant crypt foci, precursors of colonic adenoma, are frequently positive for glutathione-S-transferase P1-1. Because deoxycholic acid is an apoptosis-inducing xenobiotic in the colon, we examined the possibility that aberrant crypt foci, through the cytoprotecting function of glutathione-S-transferase P1-1, resist deoxycholic acid-induced apoptosis, thereby surviving to become adenomas and subsequently cancer. METHODS: Glutathione-S-transferase P1-1 or cyclooxygenase-2 expression and the percentage of apoptotic cells in aberrant crypt foci were examined by immunohistochemistry and by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, respectively. Glutathione-S-transferase P1-1 was transfected into colon cancer cells (M7609) and human lung fibroblasts, and deoxycholic acid-induced apoptosis was evaluated by a dye-uptake assay and flow cytometry. Binding of deoxycholic acid to glutathione-S-transferase P1-1 was analyzed by circular dichroism and immunoprecipitation. Caspase activities were determined by colorimetric protease assay, and sulindac binding to glutathione-S-transferase P1-1 was determined by inhibition assay of glutathione-S-transferase P1-1 activity. RESULTS: Aberrant crypt foci showed positive immunostaining for glutathione-S-transferase P1-1 but negative staining for cyclooxygenase-2. The percentage of apoptotic cells in aberrant crypt foci was significantly lower than in healthy epithelium, and the difference became more apparent with deoxycholic acid treatment. The impaired sensitivity of aberrant crypt foci to deoxycholic acid was restored by the glutathione-S-transferase P1-1-specific inhibitor gamma-glutamyl-S-(benzyl)cysteinyl-R-phenylglycine diethylester. By transfection of glutathione-S-transferase P1-1, M7609 cells became more resistant to deoxycholic acid-induced apoptosis than mock transfectants. Direct binding of glutathione-S-transferase P1-1 to deoxycholic acid was proven by circular dichroism and by immunoprecipitation. The aberrant crypt foci in adenoma patients treated with sulindac, which was shown to bind to glutathione-S-transferase P1-1, underwent apoptosis in 4 days and mostly regressed in 2-3 months. CONCLUSIONS: Glutathione-S-transferase P1-1 protects aberrant crypt foci from deoxycholic acid-induced apoptosis and may play a pivotal role in early colon carcinogenesis.
Adenoma↗
Binding of antibiotics to human liver glutathione S-transferases.
Glutathione S-transferases (GSH S-transferases) are multifunctional enzymes and are known to play an important role as intracellular binding protein in human liver. Binding of several antibiotics, including cefotetan, benzylpenicillin, cefazolin, chloramphenicol and gentamicin, to cationic and anionic GSH S-transferases isolated from human liver, and to human serum albumin, has been investigated by using the centrifuge column technique, which is supposed to be an excellent one for its sensitivity and rapidity in ligand binding studies. The dissociation constants (Kd) of the antibiotics for human liver GSH S-transferases and for human serum albumin, and the number of binding sites for the antibiotics on a molecule of human liver GSH S-transferases and of human serum albumin have been evaluated by means of Scatchard plots. This study has shown that cefotetan is bound to cationic GSH S-transferases to the greatest extent, followed by benzylpenicillin, cefazolin and chloramphenicol, gentamicin being bound to the smallest extent. It has been confirmed that not only cationic GSH S-transferases but also anionic GSH S-transferases have the binding capacity to the antibiotics, and that the extent of binding of the antibiotics to anionic GSH S-transferases is similar to the one to cationic GSH S-transferases. Therefore, anionic GSH S-transferases are supposed to play nearly the same role as cationic GSH S-transferases in transport of the antibiotics in human liver. The fact that the extent of binding of the antibiotics to human liver GSH S-transferases is closely correlated with the extent of biliary excretion of the antibiotics suggests that human liver GSH S-transferases play an important role in the transport of certain antibiotics from plasma, through hepatocytes, into bile.
Anions↗
Amino acid residue at codon 268 determines both activity and nucleotide-sugar donor substrate specificity of human histo-blood group A and B transferases. In vitro mutagenesis study.
Histo-blood group A transferase produces A antigens and transfers GalNAc to the acceptor substrate, H structures of glycolipids and glycoproteins. B transferase transfers galactose in place of GalNAc to the same acceptor substrate to synthesize B antigens. We have previously identified four amino acid substitutions between human A and B transferases. Out of these four, substitutions at the last two positions (codons 266 and 268) were found to be crucial for the different donor nucleotide-sugar specificities between A and B transferases as analyzed by gene transfer of chimeric A-B transferase genes. In the present study, we have in vitro mutagenized codon 268 of these two transferase cDNA expression constructs (glycine and alanine in A and B transferases, respectively) and produced substitution constructs with every possible amino acid residue at this position. We examined the activity and specificity of each construct by gene transfer followed by immunodetection of A and B antigens and in vitro enzymatic assay. Amino acid substitution constructs on the A transferase backbone with alanine, serine, and cysteine expressed enzymes with A and B transferase activities. Weak A activity was detected with histidine and phenylalanine constructs while weak B activity was detected with asparagine and threonine constructs. All the other amino acid substitutions at codon 268 on the A transferase backbone showed neither A nor B activity. The glycine construct on the B transferase backbone expressed both A and B transferase activities. Some substitution constructs on the B transferase backbone maintained B activity while some other substitutions abolished the activity. These results show that the side chain of the amino acid residue at 268 of the human A and B transferases is responsible for determining both activity and nucleotide-sugar donor substrate specificity and strongly suggest its direct involvement in the recognition of and binding to the sugar moiety of the nucleotide-sugars.
Amino Acids↗
Reduced expression of glutathione S-transferase Yb2 during progression of chemically induced hepatocellular carcinomas in Fischer 344 rats.
We followed the expression of several glutathione S-transferase subunits in altered foci, liver neoplasms and metastases produced in male Fischer 344 rats by a modified Solt-Farber protocol, to determine whether components of the resistant phenotype are lost during neoplastic progression. At 6 mo after initiation, altered foci and persistent nodules displayed increased immunohistochemical expression of glutathione S-transferase subunits Yf (pi-class), Ya (alpha-class) and Yb1 (mu-class) in comparison with normal or surrounding liver tissue. However, although most altered foci exhibited little change in glutathione S-transferase Yb2 (mu-class) subunit expression, 5% of Yf-positive foci and nodules were partially or completely deficient in Yb2 expression. At 12 and 18 mo after initiation, most grossly visible hepatocellular tumors retained induced expression of glutathione S-transferase subunits Yf, Ya and Yb1, but 63% of the carcinomas, 88% of the primary metastatic carcinomas and 94% of the pulmonary metastases were deficient in Yb2 expression. These differences in glutathione S-transferase subunit expression were confirmed by quantitative analysis by reverse-phase HPLC of S-hexylglutathione affinity-purified glutathione S-transferases from advanced tumors. Cytosolic glutathione S-transferase activity for trans-4-phenyl-3-buten-2-one in advanced tumors ranged from 42% to 66% of the activity in matched surrounding liver, whereas glutathione S-transferase activities for 1-chloro-2,4-dinitrobenzene were increased by 140% to 161%. These studies demonstrate that progression of hepatocellular carcinomas in the resistant hepatocyte model of carcinogenesis in which several glutathione S-transferase subunits are induced is associated with the loss of a major constitutive mu-class hepatic glutathione S-transferase. Although the mechanism and role of the reduction or loss of glutathione S-transferase Yb2 during malignant progression are unknown, we propose that loss of glutathione S-transferase Yb2 in some preneoplastic populations of hepatocytes might be conducive to further DNA damage by presently unknown environmental or endogenous compounds that are normally detoxified preferentially by glutathione S-transferase isoenzymes containing this subunit.
Animals↗
Glutathione S-transferases in human testicular germ cell tumors: changes of expression and activity.
Glutathione S-transferases are involved in the detoxification of carcinogens and xenobiotics and are potentially associated with the development of drug-resistance. Forty-six testicular germ cell tumors and 33 adjacent normal testicular tissue specimens were analyzed at the RNA level for the expression of glutathione S-transferase alpha and pi. Glutathione S-transferase alpha was expressed in 31 of the 33 normal testicular tissues (94%) but in only three of the 46 germ cell tumors (7%). Glutathione S-transferase pi mRNA was detected in all normal and malignant testicular tissue samples. Thirteen testicular germ cell tumors and eight normal testicular tissue samples were analyzed at the protein level. The mean specific activity of total cytosolic glutathione S-transferase in tumor tissue was decreased by about 80% as compared to normal testicular tissue. Protein analysis of the glutathione S-transferase subunits of normal testicular tissue demonstrated the presence of the glutathione S-transferase classes alpha, mu and pi, with a predominance of the mu class. In testicular germ cell tumors the glutathione S-transferase subunit pattern showed a predominance of glutathione S-transferase pi representing 88% +/- 3% of total glutathione S-transferase. Since all three glutathione S-transferase isoenzyme classes contribute to the resistance to antineoplastic drugs, the altered glutathione S-transferase isoenzyme pattern and the decrease of glutathione S-transferase activity may play a role in the high inherent drug sensitivity of human testicular germ cell tumors.
Glutathione Transferase↗
Glycosyl transferases of baby-hamster-kidney (BHK) cells and ricin-resistant mutants. N-glycan biosynthesis.
Five cell lines of ricin-resistant BHK cells have been assayed for gross carbohydrate analysis of cellular glycoproteins, for the activities of several glycosidases and of specific glycosyl transferases active in assembly of N-glycans of glycoproteins. The latter enzymes include sialyl transferase using asialofetuin as glycosyl acceptor, fucosyl transferases using asialofetuin and asialoagalactofetuin acceptors, galactosyl transferases using ovalbumin, ovomucoid and N-acetylglucosamine as acceptors and N-acetylglucosaminyl transferases using ovalbumin and glycopeptides as acceptors. Cell line RicR14, binding less ricin than normal BHK cells, contains reduced amounts of sialic acid, galactose and N-acetylglucosamine in cellular glycoproteins and lacks almost completely N-acetylglucosamine transferase I, an essential enzyme in assembly of ricin-binding carbohydrate sequences of N-glycans. These cells also contain reduced levels of N-acetylglucosamine transferase II active on a product of N-acetylglucosamine transferase I action. Sialyl transferase activity is severely depressed while fucose-(alpha 1 leads to 6)-N-acetylglucosamine fucosyl transferase activity is increased. Cell lines RicR15, 17, 19 and 21 showed partial deficiencies in galactosyl and N-acetylglucosaminyl transferases. A hypothesis is put forward to account for the different carbohydrate compositions and ricin binding properties of glycoproteins synthesised by these cells in terms of the determined enzyme defects, the normal level of sialyl transferases detected in RicR15 and RicR21 cells and the elevated levels of sialyl and fucosyl transferases detected in RicR17 and 19 cells. None of the above changes in glycosyl transfer reactions in the RicR cell lines are due to enhanced glycosidase or sugar nucleotidase activities in the mutant cells.
Animals↗
Murine monoclonal antibodies directed to the human histo-blood group A transferase (UDP-GalNAc:Fuc alpha 1----2Gal alpha 1----3-N-acetylgalactosaminyltransferase) and the presence therein of N-linked histo-blood group A determinant.
Mouse MAbs (WKH-1 through -3) to the human histo-blood group A glycosyltransferase (Fuc alpha 1----2Gal alpha 1----3 galactosaminyltransferase) were established by immunization with the purified native A transferase protein. Hybridomas were selected on the basis of solid-phase reactivity with the purified native A transferase, cell immunofluorescence and immunoprecipitation of transferase activity, and absence of reactivity with blood group ABH carbohydrate determinants. Three MAbs, thus selected, were found most likely to react with the protein epitopes unrelated to carbohydrate epitopes of purified A transferase. The MAbs reacted with cells having high A transferase activity and immunoprecipitated the A transferase activity as well as the 40,000 MW iodinated transferase protein. The antibodies were shown, however, to immunoprecipitate and partially inhibit not only A1 and A2 but also B transferase activity from plasma and A transferase from human lung, and to react with B cells expressing B transferase, thus indicating a cross-reactivity with B transferase. In contrast, they showed no reactivity with various cells having the O phenotype and did not immunoprecipitate the A transferase from porcine submaxillary glands or the alpha 1----2fucosyltransferase from Colo205 cells. The purified A glycosyltransferase was found to carry blood group A carbohydrate determinants by immunochemical detection with a panel of anti-carbohydrate MAbs. These determinants are believed to be N-linked, since treatment of the purified A transferase with N-glycanase removed activity. Immunohistological studies of three epithelial tissues showed that the antibodies stained the Golgi area of cells in epithelia from A and B, but not O, individuals.
ABO Blood-Group System↗
Alteration of hepatic glutathione S-transferases and release into serum after treatment with bromobenzene, carbon tetrachloride, or N-nitrosodimethylamine.
The effects of bromobenzene, carbon tetrachloride, and N-nitrosodimethylamine (DMN) on hepatic glutathione S-transferase activity were studied in untreated and in phenobarbital- or ethanol-treated rats. In phenobarbital-treated rats, the isozymic composition of the hepatic cytosolic glutathione S-transferases was changed after giving hepatotoxic chemicals; glutathione S-transferases 2-2(AA), 3-3(A), 1-2(B), 3-4(C), and 4-4 + 5-5(D + E) were present in cytosol from control rats, but only glutathione S-transferases cochromatographing with transferases 4-4 + 5-5(D + E) were detected in rats given carbon tetrachloride or bromobenzene. A marked decrease in hepatic and an increase in serum glutathione S-transferase activity were also observed after carbon tetrachloride or bromobenzene treatment, but little change was seen after giving DMN. On the contrary, in untreated or ethanol-treated rats, DMN administration decreased hepatic glutathione S-transferase activity and caused an elevation in serum glutathione S-transferase activity. The isozymic composition of the hepatic cytosolic glutathione S-transferases after giving DMN to untreated rats was also altered, but the alteration was much less than that observed after giving carbon tetrachloride or bromobenzene to phenobarbital-treated rats. The elevation in serum glutathione S-transferase activity was accompanied by an increase in both serum glutamate-pyruvate transaminase activity and serum bilirubin concentrations. Thus, hepatic glutathione S-transferase activity was altered and released into serum after giving hepatotoxic chemicals, and the alteration in glutathione S-transferase activity was dependent on treatment with phenobarbital or ethanol.
Animals↗