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1.
Despite the fact that a number of alterations of the hypothalamic-pituitary-gonadal hormone axis have been identified in patients with testicular cancer, little is known about the gonadotrophin secretion pattern in such patients who have greatly increased human chorionic gonadotrophin (hCG) serum concentrations. The aim of this study was to assess this issue in detail using a longitudinal study design and a panel of highly sensitive and specific immunoassays. Eleven patients with non-seminomatous (n=11), and one with seminomatous testicular cancer with pretreatment hCG serum concentrations exceeding 10(5) pg/ml (>1000 mIU/ml) were selected and followed for a mean of 166 days (mean of 14 serum samples/patient) after initial diagnosis. Serum concentrations of hCG, its free alpha- (hCGalpha) and beta- (hCGbeta) subunits, human follicle-stimulating hormone (hFSH) and human luteinizing hormone (hLH) were determined by highly sensitive and specific enzymometric immunoassays based on a panel of monoclonal antibodies (MCA) established in our laboratory. A potential FSH-like activity (FSA) of hCG in the respective sera was determined by radioreceptor assays (RRA) for LH/CG and FSH. Specificity of FSA at the level of the receptor was assessed by MCA-based immunoabsorption studies. At diagnosis, hCG (9.8x10(7)+/-4.84x10(7) pg/ml; range 1.1x10(5)-5x10(8) pg/ml) was greatly increased and serum hFSH was undetectable (<9 pg/ml) in 11 patients, and one patient had very low, albeit detectable (approximately 30 pg/ml) hFSH concentrations. hLH was below the limit of detection (<2 pg/ml) in five individuals. During successful chemotherapy, hCG rapidly declined to physiological concentrations and hFSH/hLH returned to normal or even reached supraphysiological values. There was a highly significant negative correlation between hCG and hFSH (P=0.0001) and, to a lesser extent, hLH (P=0.0265). The ability of serum hCG to block the binding of [125I]rFSH (rat FSH) to its receptor was found to be 0.01-0.1% compared with the FSH standard; this could be reversed by an anti-hCG MCA. Addition of a specific MCA against hFSH blocked 3 microg/ml of the hFSH standard, but had no effect on the FSA of serum hCG in the FSH RRA. As observed during pregnancy, secretion of gonadotrophin -- particularly that of FSH -- is substantially or completely suppressed in patients with testicular cancer when serum hCG concentrations exceed 10(5)-10(6) pg/ml (approximately 10(3)-10(4) mIU/ml). As determined by RRA, the intrinsic FSA of tumour-derived hCG is most probably responsible for the suppression of hFSH in this group of patients with testicular cancer.  相似文献   

2.
Trophoblast invasion into the uterine wall is controlled by many factors. Previously, a human chorionic gonadotropin (hCG) receptor has been found to be expressed on invasive trophoblast as well as on choriocarcinoma cells implying a possible role for the hormone in trophoblast invasion. Therefore, this study examined the role of hCG in the invasion of trophoblastic (JEG-3) cells. Increasing hCG concentrations were applied in a trophoblast invasion model, JEG-3, through matrigel-coated filters. The proliferation was quantified by WST-1 cleavage assay. Cell migration was studied by examining the number of cells that had passed the uncoated porous (8-microm pore size) filters. After staining, filters were examined microscopically for cells on the underside of the membrane. A quantitative protease assay was also performed. Flow cytometric analysis of alpha5 and alpha6 integrin subunits, which are essential for interactions between cells and extracellular matrix, was performed. hCG increased significantly (P<0.01) the in vitro invasion of trophoblastic JEG-3 cells in a dose-dependent manner. Migration was also increased by hCG (P<0.01). However, cell proliferation remained unchanged. The second messenger analogue dibutyryl cAMP (db cAMP) and the cAMP elevating factor (forskolin) mimicked the effects of hCG by stimulating a dose-dependent increase of trophoblastic cell UEG-3) invasion. The collagenolytic activity of trophoblastic cells (EG-3) was increased by hCG stimulation. No changes were shown in the expression of alpha5 and alpha6 integrin subunits on JEG-3 cells. In vitro hCG is a regulatory factor of invasion and migration in trophoblastic JEG-3 cells, whereas proliferation is not influenced. The endogenous production of hCG by the trophoblast in vivo implies an autocrine control of invasion processes by hCG.  相似文献   

3.
Using a highly sensitive bioassay for TSH, in which human thyroid follicles incorporate 125I and release de novo synthesized thyroid hormone into the culture medium, the thyrotropic activities of various hCG preparations were studied. Under the culture conditions employed, bovine TSH (bTSH) was approximately 6- to 9-fold more active than human TSH (hTSH). Highly purified hCG prepared from urine of normal pregnant women (CR 127) had only a trivial thyrotropic activity equipotent to 0.00022 microU bTSH/U hCG or 0.0013 microU hTSH/U hCG (19.7 microU hTSH/mg hCG). Hybrid hCG (AB1ER) also elicited low thyrotropic activity (14.0 microU hTSH/mg), whereas crude hCG had moderate thyrotropic activity (0.041 hTSH microU/U hCG or 127 microU/mg protein). Deglycosylated hCG, a very weak LH/hCG receptor agonist, was the most potent agonist in thyroid follicles (588 microU hTSH/mg protein). hCGs purified from urine of patients with trophoblastic tumors had greater TSH-like activity (37-84 microU hTSH/mg protein) than purified hCG. Asialo-hCG purified from a patient with choriocarcinoma had very potent TSH-like activity (468 microU hTSH/mg). Submaximal doses of bTSH and hCG variants produced additive stimulation of thyroid function. Furthermore, the thyrotropic effect of hCG was inhibited by anti-TSH receptor antibody obtained from patients with myxedema. These in vitro findings suggest that although hCG is reported to exert potent cAMP-stimulating activity on rat thyroid-like cells (FRTL-5) and Chinese hamster ovary cells transfected with hTSH receptor complementary DNA (0.092-0.72 microU hTSH/U hCG), the thyrotropic activity induced by authentic hCG in human thyroid follicles is too weak to cause hyperthyroidism in normal pregnancy. However, hCG produced by some trophoblastic tumors, particularly asialo-hCG, has potent thyrotropic activity sufficient to cause clinically overt hyperthyroidism when produced excessively.  相似文献   

4.
Human chorionic gonadotropin (hCG) in first trimester placental cells is composed of immature alpha- and beta-subunits containing only N-linked high-mannose sugar chains. Intracellular immature intermediates are accumulated in rough endoplasmic reticulum in much greater quantity than mature hCG composed of mature subunits. We have previously shown that this immature hCG might be bound to other protein(s), including an ATP-binding protein, forming high molecular weight-hCG (HMW-hCG), which is not aggregate of immature hCG alone. To identify the ATP-binding protein forming the HMW-hCG in detail, proteins in HMW-hCG preparation were photoaffinity-labeled with 8-azido-[alpha-32P]ATP. Autoradiography followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the labeled protein with M(r) = 78000 was immunoprecipitated with any antibody against alpha-subunit, beta-subunit and hCG, indicating that this protein is bound to immature hCG. Furthermore, to determine whether some other proteins associate to form HMW-hCG, we purified HMW-hCG without breakdown to its components using columns of DE52, Heparin-Sepharose and Sephacryl S-300. As the final step of the purification, HMW-hCG was allowed to adsorb on a column of ATP-agarose and anti-hCG IgG-agarose, respectively. SDS-PAGE analysis of eluted proteins from the columns bound to the respective column via the constituent of HMW-hCG, such as ATP-binding protein or immature hCG, showed four common protein bands with molecular weights of 78000, 43000, 28000 and 20000. The protein with M(r) = 43000 was stained with any antibody against alpha-subunit, beta-subunit and hCG, indicating it to be immature hCG. The protein band with M(r) = 78000, which might correspond to the ATP-binding protein described above, was stained with anti-heat shock protein 70 (HSP70) monoclonal antibody. To confirm the association of immature hCG and HSP70-like protein, immature hCG preparation was incubated with HSP70-like protein purified from placental extracts. The molecular weight change of immature hCG appeared to increase by this incubation and was close to HMW-hCG, but not exactly the same. These results suggest that immature hCG intermediate exists as HMW-hCG containing HSP70-like protein, which has ATP-binding capacity, and two other proteins in first trimester placental cells.  相似文献   

5.
6.
We have demonstrated the expression of membrane-associated hCG and its subunits and fragments by cells from 78 human cancer cell lines of different types and origins, indicating that such expression is a common phenotypic characteristic of cultured human malignant cells. Because human (h) LH beta has 80% homology with hCG beta and is coded by one of the seven genes in the gene cluster located in chromosome 19, it was important to determine whether hLH and its beta-subunit are also expressed as membrane-associated proteins by cells from human cancer cell lines. Thus, 11 cancer cell lines of different types and origins were adapted to grow in serumless medium, with Nutridoma-HU or SP as serum substitute, and analyzed by flow cytometry using two monoclonal antibodies directed to different conformational epitopes of intact hLH and a monoclonal antibody reacting with an epitope of hLH beta-free. The cells were also analyzed simultaneously for the expression of hCG and its subunits and fragments. Determination of translatable levels of hLH beta and hCG beta messenger RNAs (mRNAs) was performed in cells from some of the cancer cell lines, including the JEG-3 choriocarcinoma cell line, and in cells from a human fetal lung cell line. The analytical flow cytometry studies showed that in addition to the expression of membrane-associated hCG in all of its forms, expression of membrane-associated intact (holo) hLH and its free beta-subunit occurred in every case. These findings were corroborated by the presence of translatable levels of hLH beta and hCG beta mRNAs in all of the cancer cell lines analyzed, indicating that the expression of these membrane-associated glycoproteins is a phenotypic characteristic of human cancer cells and that the activation of the hCG beta-hLH beta gene cluster is nonselective. The presence of translatable levels of hCG beta-hLH beta mRNAs in the cultured human fetal lung cells punctuates once more the in vivo and in vitro biochemical similarities between fetal and cancer cells.  相似文献   

7.
Hyperthyroidism or increased thyroid function has been reported in many patients with trophoblastic tumors. In these cases, greatly increased human chorionic gonadotropin (hCG) levels and suppressed TSH levels suggest that hCG has thyrotropic activity. Recent investigations have clarified the structural homology not only in the hCG and TSH molecules but also in their receptors, and this homology suggests the basis for the reactivity of hCG with the TSH receptor. The clinical significance of the thyrotropic action of hCG is now also recognized in normal pregnancy and hyperemesis gravidarum. Highly purified hLH binds to recombinant hTSH receptor and is about 10 times as potent as purified hCG in increasing cAMP. The beta-subunits of hCG and hLH share 85% sequence identity in their first 114 amino acids but differ in the carboxy-terminal peptide because hCG beta contains a 31-amino acid extension (beta-CTP). A recombinant mutant hCG that lacks beta-CTP showed almost identical potency to LH on stimulation of recombinant hTSH receptor. If intact hCG were as potent as hLH in regard to its thyrotropic activity, most pregnant women would become thyrotoxic. One of the roles of the beta-CTP may be to prevent overt hyperthyroidism in the first trimester of pregnancy when a large amount of hCG is produced by the placenta. Nicked hCG preparations, obtained from patients with trophoblastic disease or by enzymatic digestion of intact hCG, showed approximately 1.5- to 2-fold stimulation of recombinant hTSH receptor compared with intact hCG. This suggests that the thyrotropic activity of hCG may be influenced by the metabolism of the hCG molecule itself. Deglycosylation and/or desialylation of hCG enhances its thyrotropic potency. Basic hCG isoforms with lower sialic acid content extracted from hydatidiform moles were more potent in activating adenylate cyclase, and showed high bioactivity/immunoactivity (B/I) ratio in CHO cells expressing human TSH receptors. This is consistent with the finding that the beta-CTP truncated hCG with higher thyrotropic potency is substantially deglycosylated and desialylated in the beta-subunit relative to intact hCG because all four O-linked glycosylation sites occur within the missing C-terminal extension. The desialylated hCG variant also interacts directly with recombinant hTSH receptors transfected into human thyroid cancer cells. There is thyroid-stimulating activity in sera of normal pregnant women, and this correlates with serum hCG levels. The thyroid gland of normal pregnant women may be stimulated by hCG to secrete slightly excessive quantities of T4 and induce a slight suppression of TSH, perhaps being about 1 mU/L less than nongravid levels, but not high enough to induce overt hyperthyroidism. Maternal thyroid glands may secrete more thyroid hormone during early pregnancy in response to the thyrotropic activity of hCG that overrides the normal operation of the hypothalamic-pituitary-thyroid feedback system. Biochemical hyperthyroidism associated with hyperemesis gravidarum has been attributed to hCG. In patients with hyperemesis gravidarum, thyrotropic in serum correlated with hCG immunoreactivity, and the severity of vomiting as indicated by clinical and biochemical parameters correlated with the degree of thyroid stimulation. To understand the thyrotropic action of hCG, it is necessary to know whether hCG activates the same domain of the TSH receptor as does TSH. The identification of the molecular structure of the hCG isoform with the highest thyrotropic potency will resolve the enigma of gestational thyrotoxicosis and the hyperthyroidism associated with trophoblastic disease and hCG-producing tumors.  相似文献   

8.
When highly purified human factor VIII is submitted to agarose gel chromatography in the presence of 0.5 M CaCl2, the procoagulant activity (low molecular weight factor VIII, LMW-F VIII) is separated from the void volume protein (Vo-VIII). Upon incubation of human factor VIII with purfied neuraminidase, a very stable platelet aggregating activity develops in the "Vo-VIII' fraction, not in the "LMS-FVIII' part. Evidence is provided that the generated aggregating activity is a property of the 'carrier protein' for LMW-F VIII. Desialylated factor VIII retains its antigenic reactivity, its procoagulant or ristocetin cofactor properties and the capacity of its subunits to dissociate and recombine. Neuraminidase-treated human factor VIII, in contrast to intact bovine factor VIII or intact human factor VIII in the presence of restocetin, does not induce aggregation of EDTA-platelet rich plasma, of congenitally afibrinogenaemic platelet rich plasma, nor of washed platelets.  相似文献   

9.
The muscle and brain creatine kinases of giant panda have been isolated and purified. The purified muscle and brain enzymes (MM and BB) are homogeneous on both the polyacrylamide gel electrophoresis in the presence and absence of SDS. Both enzymes are dimers, consisting of two identical subunits each with a molecular weight of 42,000 daltons. The characteristics of muscle and brain enzymes have been studied, respectively. The hybridized enzyme, MB, was prepared by hybridization of MM and BB. The kinetic parameters of MM, BB and MB were determined, respectively. The results from modification of SH groups show that the SH groups of panda creatine kinases are essential for their activity and among the all SH groups in the enzyme only one per subunit is essential for enzymatic activity.  相似文献   

10.
It is well known that human chorionic gonadotropin (hCG) is sometimes secreted from nontrophoblastic neoplasms. To elucidate the role of ectopic hCG, we investigated the effect of hCG produced from a papillary thyroid cancer cell line (B-CPAP cells) on stimulation and growth promotion of FRTL-5 rat thyroid cells. Ectopic hCG contained in the culture medium of B-CPAP cells was purified using gel filtration and bioassayed for thyrotropic activity in FRTL-5 cells. Addition of ectopic hCG (up to 5.2 x 10(4) IU/L) increased cyclic adenosine monophosphate (cAMP) accumulation and 3H-thymidine incorporation in FRTL-5 cells dose dependently. These effects were almost as potent as the stimulation induced by standard hCG CR-127. After the absorption of the ectopic hCG by anti-hCG-beta monoclonal antibody, the cAMP accumulation was significantly decreased. Analysis of ectopic hCG isoforms with different isoelectric points indicated the predominance of the acidic hCG isoform with isoelectric point (pI) 3.8-3.2 that is the major isoform of standard hCG. Basic isoforms (pI 5.7-5.3) with higher thyrotropic potency were also detected. These results indicate that the ectopic hCG secreted from papillary thyroid cancer cells possess intrinsic thyroid-stimulating and growth-promoting activity. The ectopic hCG may act as an autocrine-paracrine factor in nontrophoblastic neoplasms.  相似文献   

11.
BACKGROUND: Previous studies in which monoclonal antibodies (MoAbs) were used against different epitopes of human chorionic gonadotropin (hCG) demonstrated the presence of membrane-associated hCG and its subunits by cancer cells of different types and origins and by human embryonic and fetal cells. To elucidate the mechanism of action of a synthetic vaccine against hCG, experiments were conducted to determine the presence or absence of direct dose dependent cytolytic activity by hCG MoAbs, including those elicited by the vaccine. METHODS: Human adenocarcinoma cells from the uterine cervix (ATCC HeLa CCL 2.0) grown in defined media at 37 degrees C were treated for 2-3 days with different selected doses of each of 12 MoAbs directed against different epitopes of hCG. Three of these MoAbs were against three different epitopes of the synthetic hCGbeta vaccine. RESULTS: There was a direct dose dependent effect by a MoAb directed against the natural hCGbeta carboxy terminal peptide (CTP), by a MoAb directed against hCGalpha, and by one of the three MoAbs produced by the synthetic hCGbeta-CTP, which is the main component of the World Health Organization (WHO) vaccine being tested for fertility control and for cancer treatment or prevention. CONCLUSIONS: For the first time (to the authors' knowledge), these results show the existence of hCG MoAbs that have direct dose related cytotoxicity at 37 degrees C and explain the mechanism of action of the WHO anti-hCG vaccine.  相似文献   

12.
13.
A lectin from Wistaria floribunda seeds which specifically binds to N-acetyl-D-galactosamine was purified to homogeneity as judged by polyacrylamide gel electrophoresis. Its molecular weight was estimated to be 68,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. It dissociated into subunits on reduction with 2-mercaptoethanol with concomitant loss of hemagglutinating activity. On oxidation in air, the subunits reassociated into the lectin molecules with hemagglutinating activity. Carboxymethylation of the subunits with iodoacetic acid prevented their reassociation on oxidation in air. The molecular weight of the subunits was 32,000, which is about one-half that of the native lectin, suggesting that the lectin consists of two subunits. The results total, NH2-terminal, and COOH-terminal amino acid analyses, and mapping of the tryptic digest of the lectin indicated that these two subunits were indistinguishable and were probably identical, and that they were linked together covalently through a single disulfide bond. Equilibrium dialysis experiments show that the lectin and its subunit molecules are divalent and monovalent, respectively, with respect to sugar binding. The lectin is a glycoprotein, containing 3.2% carbohydrate. The carbohydrate moiety is composed of mannose, galactose, and glucosamine is a molar ratio of 1:2:1 and these sugars seem to be linked as a single oligosaccharide chain to each subunit of the protein.  相似文献   

14.
15.
Urease from Staphylococcus saprophyticus was purified more than 800-fold by liquid chromatography reaching homogeneity, as shown by isoelectric focussing, at a maximum specific activity of 1979 U/mg. The molecular weight of the native enzyme was 420,000; it consisted of subunits with molecular weights of 72,400 (alpha), 20,400 (beta), 13,900 (gamma) in an estimated (alpha beta gamma)4 stoichiometry. In native gradient polyacrylamide gel electrophoresis urease exhibited a multiple activity band pattern with molecular weights ranging from 420,000 to 100,000. In the native enzyme, 4.09 (+/- 0.25) atoms of nickel per molecule were detected. The N-terminal amino acids of the urease subunits were identical to those from Staphylococcus xylosus, and amino acid analysis revealed high similarities in both enzymes; no cysteine was detected after acid hydrolysis of vinylpyridinylated urease. Electron micrographs of negatively stained urease specimens from both staphylococci showed identical size and structure.  相似文献   

16.
When human chorionic gonadotropin (hCG) was treated with a 20-fold molar excess of N-acetylimidazole in aqueous solution, two tyrosyls were acetylated, resulting in a 50% reduction in in vivo biological activity. With increased quantities of reagent, the number of tyrosyls acetylated increased but with no further decrease in the biological activity. In vitro biological activity (binding to hCG receptors) of the hormone was not affected at all. Acetylation in urea increased tyrosyl modification, accompanied by acetylation of some lysyls, yielding a product in which all seven tyrosyls were acetylated and both in vivo and in in vitro biological activities were completely abolished. Deacylation with hydroxylamine partially restored biological activity of some but not all of the modified products. When individual hCG subunits were treated with the same reagent, the number of tyrosyls acetylated in each subunit again increased with increasing amounts of reagent, up to three in the alpha subunit and two in the beta subunit in the absence of urea. The tyrosyls in the beta subunit appeared less reactive to the reagent than those in the alpha subunit. Subunits modified to these extents retained ability to recombine as examined by gel electrophoresis, but the recombined products varied considerably in both in vivo and in vitro biological activities. A completely tyrosyl-acetylated product of hCG-alpha did not combine with intact hCG-beta, while fully modified hCG-beta did with intact hCG-alpha.  相似文献   

17.
A population of free, native ribosomal 40S subunits, that do not react with 60S subunits to form 80S ribosomes, has been identified in the postmicrosomal fraction of rat liver homogenates. A protein (IF-3) has been purified from high salt (0.88 M KCI) extracts of native 40S subunits by gradient centrifugation and by ammonium sulfate fractionation; it prevents the reassociation of subunits and to a limited extent dissociates ribosomes to subunits. The activity is measured by ultracentrifugation of the reaction products on linear sucrose gradients, or with an assay developed in this laboratory that couples dissociation with the 60S-specific peptidyltransferase reaction; the latter procedure measures the amount of 60S subunits released from ribosomes or remaining in incubations in the presence of IF-3. Dissociation factor activity is recovered from most of the particles that are resolved by zonal centrifugation of the total "native subunits" obtained from the postmicrosomal fraction; the highest concentration of IF-3, however, appears to be associated with native 40S subunits. The purified dissociation factor IF-3 is composed of about ten polypeptides and the molecular weight is estimated to be between 500 000 and 700 000, on the basis of glycerol and cesium chloride gradient centrifugation. When purified 40S subunits react with IF-3 or when 80S ribosomes are dissociated by IF-3, a product is formed which is dependent on the concentration of the protein factor and has the characteristics of a 40SIF-3 complex; centrifugation of the complex on sucrose and cesium chloride gradients suggests that the complex consists of 1 equiv of each of the two components. Although dissociation factor IF-3 appears to react in a specific manner with free or ribosome-associated 40S subunits, the reaction with subunits differs in several respects from that with ribosomes. The dissociation factor also appears to interact with 60S subunits but multiple complexes are formed, some with more than 1 IF-3 equiv per 60S particle. The IF-3 converts 40S dimers (55S particles) to the 40S-IF-3 complex and dissociates free, native 80S particles present in the postmicrosomal fraction, but it does not affect polysome-associated ribosomes engaged in protein synthesis.  相似文献   

18.
Sulfite ion (HSO3-) is one of the products when elemental sulfur is oxidized by the hydrogen sulfide:ferric ion oxidoreductase of Thiobacillus ferrooxidans AP19-3. Under the conditions in which HSO3- is accumulated in the cells, the iron oxidase of this bacterium was strongly inhibited by HSO3-. Since cytochrome c oxidase is one of the most important components of the iron oxidase enzyme system in T. ferrooxidans, effects of HSO3- on cytochrome c oxidase activity were studied with the plasma membranes of HSO3(-)-resistant and -sensitive strains of T. ferrooxidans, OK1-50 and AP19-3. The enzyme activity of AP19-3 compared with OK1-50 was strongly inhibited by HSO3-. To investigate the inhibition mechanism of HSO3- in T. ferrooxidans, cytochrome c oxidases were purified from both strains to an electrophoretically homogeneous state. Cytochrome c oxidase activity of a purified OK1-50 enzyme was not inhibited by 5 mM HSO3-. In contrast, the same concentration of HSO3- inhibited the enzyme activity of AP19-3 50%, indicating that the cytochrome c oxidase of OK1-50 was more resistant to HSO3- than that of AP19-3. Cytochrome c oxidases purified from both strains were composed of three subunits. However, the molecular weight of the largest subunit differed between OK1-50 and AP19-3. Apparent molecular weights of the three subunits of cytochrome c oxidases were 53,000, 24,000, and 19,000 for strain AP19-3 and 55,000, 24,000, and 19,000 for strain OK1-50, respectively.  相似文献   

19.
20.
Two forms of iron superoxide dismutase (SOD) were purified from cell extract (CE) and culture filtrate (CF) of Mycobacterium bovis BCG, respectively. The molecular weight of both enzymes was estimated to be approximately 84,000 by gel filtration, whereas that of their subunits was 21,500, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that each of purified enzymes is composed of four identical subunits. The specific activities of CE SOD and CF SOD were 3,850 and 4,040, respectively. The purified enzymes were not joined by disulfide bonds and were, to some extent, resistant to sodium dodecyl sulfate. Their activities were lost by H2O2, but not by azide and cyanide, indicating iron SODs. Enzyme activities were detectable over a broad range of pHs, from 5.0 to 9.0, and were stable for 6 months at -20 degreesC. Each value of pI was 4.5. In Western blots, both enzymes reacted with sera of tuberculosis patients, but not with normal sera. The N-terminal amino acid sequences of CE SOD and CF SOD were the same, suggesting that there is no N-terminal signal sequence.  相似文献   

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