Chromatographic heterogeneity of FDP aldolase and lactate dehydrogenase of rabbit tissues: use of DEAE-cellulose in separation of isomeric forms of aldolase.
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A radioimmunoassay available for human aldolase A was developed for the direct quantification of aldolase A in human serum and tissues. The method was a double antibody technique using radio-iodinated purified aldolase A, chicken antibody to aldolase A, and rabbit antibody to chicken IgG. This radioimmunoassay was specific for the aldolase A subunit, with no cross-reactivity with human aldolase B subunit or human aldolase C subunit. Aldolase A was predominantly high in skeletal muscle, and relatively high in brain and cardiac muscle. Normal liver tissue contains only a small amount of aldolase A, whereas aldolase A predominates in liver cell carcinoma tissue. Aldolase A levels in the sera of normal subjects were 171 +/- 39 ng/ml (mean +/- 2SD). Aldolase A levels correlated closely with hemoglobin levels, so aldolase A levels were increased in the sera with hemolysis. Since skeletal muscle is the largest origin of aldolase A in any tissue, serum aldolase A levels were increased in patients with acute muscle injury due to abdominal operation and even in healthy subjects after hard exercise. Serum aldolase A levels in almost all of non-cancer patients of the digestive tract were less than 210 ng/ml. In contrast, about 80% of patients with cancer in the digestive tract showed increased serum aldolase A levels. Aldolase A levels were remarkably increased in the sera of cancer patients with distant metastasis. The CEA levels were increased only in 46% of the sera of patients with cancer in the digestive tract, whereas the aldolase A levels were increased in 86% of the patients. The AFP levels were higher than 100 ng/ml in 76% of the sera of 21 patients with liver cell carcinoma, whereas the aldolase A levels were markedly increased in 90% of them. From these results, it may be suggested that the determination of serum aldolase A by radioimmunoassay is a useful tool in the clinical diagnosis of cancer patients with cancer in the digestive tract.
We studied the alteration of aldolase isozymes in the serum and tissues of patients with cancer and other diseases using radioimmunoassays specific for aldolase A, B, and C subunits. Aldolase B was predominantly found in adult liver, where aldolase A and C were distinctly low. Aldolase A and B showed almost the same concentration in fetal liver, while in neonatal liver aldolase B protein concentrations were much higher than aldolase A. In contrast, aldolase A was the predominant isozyme found in hepatoma and gastric cancer tissues, whereas aldolase B was distinctly low in hepatoma tissues, and extremely low in gastric cancer tissues. These results suggest that the aldolase A is a more fetal type of liver isozyme than the aldolase B and C, and aldolase B is a more differentiated type of liver isozyme than aldolase A and C. Serum FDP aldolase activities were elevated in half of patients with liver diseases, all patients with muscle diseases and a few patients with cancer. Serum aldolase A levels were elevated in patients with muscle diseases and cancer, but not elevated in patients with liver diseases. In contrast, serum aldolase B levels were elevated in patients with liver disease, but not elevated in patients with muscle diseases and other diseases without liver injury. Serum aldolase B levels showed a trend to decrease in cancer patients with normal GPT levels. Serum aldolase A/B ratios were significantly increased in cancer patients with normal GPT levels, whereas they showed the decreased levels in patients with liver diseases.(ABSTRACT TRUNCATED AT 250 WORDS)
A solid-phase, noncompetitive radioimmunoassay has been developed for aldolase B in human serum and tissues. Aldolase B was purified from human liver, and specific antisera to purified aldolase B were obtained from chickens. Specific antihuman aldolase B IgG was purified by affinity chromatography. Disposable polypropylene plates were coated with affinity purified specific IgG antibody and used for radioimmunoassay with 125I-specific IgG antibody to aldolase B. The nonspecific binding was minimized by saturating the binding sites of the plates with 2% ovalbumin in 0.1% Tween 20. This radioimmunoassay is specific for the aldolase B subunit, with no cross-reactivity with human aldolase A or aldolase C subunits. Aldolase B is predominantly found in normal liver. Relatively high aldolase B levels are also observed in kidney. Serum levels of aldolase B in 21 normal subjects ranged from 21 to 39 ng per ml, with a mean of 28.7 +/- 8.6 (2 S.D.) ng per ml. Forty of 42 (95%) patients with acute and chronic hepatitis without cirrhosis had serum aldolase B levels greater than 40 ng per ml. Serum aldolase B levels correlated well with total serum aldolase enzyme activities (r = 0.967) and SGPT (r = 0.951) in patients with liver diseases. In cancer patients, serum aldolase B was slightly elevated in 15 of 26 (58%) patients with cancer metastatic to the liver or primary liver cell carcinoma, whereas no elevation of serum aldolase B was observed in 16 cancer patients without liver metastasis. Measurements of aldolase B serum levels by radioimmunoassay appear to be a useful measure of liver cell necrosis from benign or malignant liver diseases.
Reductive, nonreductive, and photolytic interactions of vanadate with fructose-1,6-bisphosphate aldolase were examined and used to explore the interactions of oxoanions with aldolase. Aldolase is known to interact strongly with oxoanions at low ionic strength and weakly at higher ionic strength. Oxoanions inhibit aldolase competitively with respect to fructose 1,6-bisphosphate although the location of the oxoanion binding site on aldolase remains elusive. In this work, the interaction of aldolase with a series of oxoanions was compared at ionic strength approaching physiologic levels. The size and shape of the anion were important for the effective binding to aldolase, and no significant increase in affinity for aldolase was observed by the addition of alkyl groups to the oxoanions. Vanadate competitively inhibits aldolase in a manner analogous to the other oxoanions. Since vanadate solutions contain a mixture of vanadate oxoanions, the nature of the inhibition was determined using a combination of enzyme kinetics and 51V NMR spectroscopy. Aldolase contains a significant number of thiol functionalities, and as expected, vanadate undergoes redox chemistry with them, generating an irreversibly inhibited aldolase. This oxidative chemistry was attributed to the vanadate tetramer, whereas vanadate dimer was a reversible inhibitor. Vanadate monomer does not significantly interact with aldolase reversibly or irreversibly. Vanadyl cation has the lowest inhibition constant under these high ionic strength conditions. Using Yonetani-Theorell analysis, it appears that phosphate, pyrophosphate, and sulfate bind to the same site on aldolase, whereas vanadate, arsenate, and molybdate bind to another site. UV light-induced photocleavage of aldolase by vanadate was examined, and the loss of aldolase activity was correlated with cleavage of the aldolase subunit. Further studies using vanadium as a probe should reveal details on the location of the vanadate and vanadyl cation binding sites. This study suggests several sites on aldolase will accommodate oxoanions, and one of these sites also accommodates vanadyl cation.
Radioimmunoassays specific for fructose-1, 6-diphosphate aldolase isozymes were developed for the quantification of human aldolase A, B and C. The method is a double-antibody radioimmunoassay using radioiodinated purified aldolase A, B and C as ligand, chicken antibodies to aldolase A, B and C, and rabbit antibodies to chicken IgG. The Iodogen method was used for the iodination of aldolase A, B and C in this study. Aldolase A was predominantly high in concentration in muscle, aldolase B was high in normal adult liver, and aldolase C was high in adult brain. Aldolase A was elevated in hepatoma tissue and hepatoma cell lines, where aldolase B was distinctly low. Normal serum levels for the three isozymes were determined. The aldolase A levels in serum obtained from 41 normal subjects were 170 +/- 39 ng/ml. Serum aldolase A levels were increased in many patients with cancer and muscle diseases, but were not increased in patients with hepatitis or other benign diseases. Serum aldolase B levels obtained from 11 normal subjects were 28.5 +/- 9.2 ng/ml. Serum aldolase B levels were increased in patients with hepatitis and correlated well with serum GPT levels. Serum aldolase C levels obtained from 12 normal subjects were 2.4 +/- 0.7 ng/ml. The determination of aldolase A, B and C by radioimmunoassay may be a valuable tool in biochemical and clinical studies of aldolase isozymes.
Subunit specific radioimmunoassay for aldolase isozymes were developed for the quantification of human aldolase A and B. Aldolase B immunoreactivities were predominantly high in adult normal liver, while aldolase A was distinctly low. Aldolase A was high, while aldolase B was low in neonatal liver compared with the adult liver. Aldolase A immunoreactivities were almost the same as those of aldolase B in fetal liver (28 weeks). Aldolase A was predominantly found in human hepatoma tissues, whereas aldolase B was distinctly low in the same hepatoma tissues. With regard to human hepatoma cell lines, aldolase A was also predominantly found in HepG2 and PLC/PRF/5 cell lines, whereas aldolase B levels were extremely low. Almost the same results were obtained from mRNA expression of aldolase A and B in human hepatoma cell lines by the method of northern hybridization. Effects of various reagents on differentiation of hepatoma cell lines were investigated. Neither Dimethyl Sulfoxide (DMSO) and 12-O-Tetradecanoylphorbol-13-acetate (TPA), which are known to be the inducers of differentiation of human leukemia cell lines such as HL-60, nor Transforming Growth Factor-beta 1 (TGF-beta 1) and Hepatocyte Growth Factor (HGF), which are known to be growth inhibitors, could cause the differentiation of hepatoma cell lines in the alteration of aldolase isozymes. The same data were shown in mRNA expression of aldolase isozymes. These results suggest that aldolase A immunoreactivities and mRNA expression are both predominantly high in hepatoma cell lines, and the reagents such as DMSO, TPA, TGF-beta 1 and HGF which tried to differentiate the hepatoma cell lines used in this study were not effective in the alteration of aldolase isozymes.
Fructose 1,6-bisphosphatase (FBPase) is known to form a supramolecular complex with alpha-actinin and aldolase on both sides of the Z-line in skeletal muscle cells. It has been proposed that association of aldolase with FBPase not only desensitizes muscle FBPase toward AMP inhibition but it also might enable the channeling of intermediates between the enzymes [Rakus et al. (2003) FEBS Lett. 547, 11-14]. In the present paper, we tested the possibility of fructose 1,6-bisphosphate (F1,6-P(2)) channeling between aldolase and FBPase using the approach in which an inactive form of FBPase competed with active FBPase for binding to aldolase and thus decreased the rate of aldolase-FBPase reaction. The results showed that F1,6-P(2) is transferred directly from aldolase to FBPase without mixing with the bulk phase. Further evidence that F1,6-P(2) is channeled from aldolase to FBPase comes from the experiments investigating the inhibitory effect of a high concentration of magnesium ions on aldolase-FBPase activity. FBPase in a complex with aldolase, contrary to free muscle FBPase, was not inhibited by high Mg(2+) concentrations, which suggests that free F1,6-P(2) was not present in the assay mixture during the reaction. A real-time interaction analysis between aldolase and FBPase revealed a dual role of Mg(2+) in the regulation of the aldolase-FBPase complex stability. A physiological concentration of Mg(2+) increased the affinity of muscle FBPase to muscle aldolase, whereas higher concentrations of the cation decreased the concentration of the complex. We hypothesized that the presence of Mg(2+) stabilizes a positively charged cavity within FBPase and that it might enable an interaction with aldolase. Because magnesium decreased the binding constant (K(a)) between aldolase and FBPase in a manner similar to the decrease of K(a) caused by monovalent cations, it is postulated that electrostatic attraction might be a driving force for the complex formation. It is presumed that the biological relevance of F1,6-P(2) channeling between aldolase and FBPase is protection of this glyconeogenic, as well as glycolytic, intermediate against degradation by cytosolic aldolase, which is one of the most abundant enzyme of glycolysis.
Stress dependent variations in th properties of the rat muscle aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) have been linked to the corresponding changes in the levels of proteolytic activities in rat muscle. Whole-body X-irradiation of rat was shown to result in loss of muscle aldolase activity towards fructose 1,6-bisphosphate by 50% while fructose 1-phosphate activity remained unchanged (Pote, M.S. and Altekar, W. (1980) Ind. J. Biochem, Biophys. 17, 255-262). Incubation of muscle extract of irradiated rat with that from control rat or rabbit muscle aldolase caused similar changes in aldolase activity. The changes are attributed to the action of catheptic enzymes possessing latency characteristics and capable of using aldolase as a substrate; the time course of their increase after irradiation corresponds to that of loss in muscle aldolase activities. Exposure of rats to stress resulted in an increase in the 'free' proteolytic activity, and the concomitant loss of 'bound' activity in muscle lysosomes indicates labilization of lysosomal membrane. The observed degradation of aldolase in vivo by muscle lysosomes is shown to be due to the action of cathepsin B (EC 3.4.22.1) present in the proteolytic enzymes released into cytosol under stress. Inactivation of rabbit muscle aldolase and rat muscle aldolase by rat muscle cathepsin B inhibited by leupeptin, antipain an iodoacetamide, but not be pepstatin. Inactivation is shown to be due to the release of C-terminal tyrosine if aldolase, required for its catalytic activity. Cathepsin B who acts as a rate-limiting enzyme in the degradation of aldolase. Such a proteolytic modification of aldolase in vivo could be relevant not only to the regulation of aldolase activity of glycolysis in muscle but also to the degradation of aldolase during stress conditions related to tissue damage and the maintenance of normal aldolase levels in the blood.
In vivo proteolytic modification of liver aldolase on administration of leupeptin, a thiol proteinase inhibitor of microbial origin, is reported. When leupeptin was injected into rats, the activity of aldolase in the liver decreased to 40% of that in control rats. Molecular properties of aldolase isolated from the livers of control rats and leupeptin-treated rats indicated that a decrease of aldolase activity is attributable to hydrolysis of a peptide linkage(s) near the carboxyterminal of the enzyme. Injection of leupeptin also caused marked increase in the activities of free lysosomal proteinases, such as cathepsin A and cathepsin D and moderate increase of cathepsin B and cathepsin L. Increase in free activity of cathepsin A returned to the level of control rats by 12 hr after injection of leupeptin, whereas 36 hr was required for recovery of decreased aldolase activity. When insulin was coinjected with leupeptin, increase in the activity of free cathepsin A and decrease of activity of aldolase produced by the injection of leupeptin was prevented. These findings indicate that modification of aldolase may be due to action of a lysosomal protease(s). Incubation of the purified aldolase with the lysosomal fraction produced the same changes in properties of aldolase as those observed in vivo on injection of leupeptin. The aldolase inactivating proteinase in the lysosomal fraction was inhibited by PMSF and leupeptin and not by pepstatin. Purified cathepsin A (a serine proteinase), cathepsin B and cathepsin L (thiol proteinase) are potent inactivators of aldolase but cathepsin H and cathepsin D are not. Cathepsin A, B and L are involved in inactivation of aldolase in lysosomes. Endogenous thiol proteinase inhibitor which inhibits lysosomal thiol proteinases (cathepsin B, L and H) is found in the cytosol fraction of liver. The level of thiol proteinase inhibitor actually decreased to 60% of that in control rats in leupeptin-treated rats, suggesting that non-thiol proteinase cathepsin A is a major factor in inactivation of aldolase in lysosomes. Not only leupeptin but also other proteinase inhibitors (antipain, E-64-D, chloroquine) caused increase of labilization of the lysosomes and decrease in aldolase activity. Physiological stimuli which are known to induce the labilization of the lysosomal membrane, such as starvation and glucagon, caused slight or no significant increase of activities of free cathepsin A and D and resulted in no apparent change in aldolase activity.
The regulation of aldolase isozyme expression during development was studied by measuring the concentrations of mRNAs coding for aldolase A and B subunits in fetal and adult rat liver. Poly(A)-containing RNAs were extracted from livers at various stages of development of fetal rats, and the aldolase A and B subunits in the in vitro translation products of these RNAs were analyzed immunologically. The content of aldolase B mRNA in 14-day fetal liver, measured quantitatively as translational activity, was somewhat smaller than that of aldolase A mRNA; immunologically precipitable aldolase B and A amounted to 0.06% and 0.25% respectively, of the total products. Similar experiments using RNAs from fetuses at later stages, however, showed that aldolase B mRNA increased during development, whereas aldolase A mRNA decreased. In newborn rat liver, aldolase B constituted 0.56% of the total translation products of mRNA, but there was little detectable aldolase A (0.03%). The changes of aldolase mRNA levels were analyzed further by northern blot and dot-blot hybridization experiments using cloned aldolase A and B cDNAs. The content of aldolase B mRNA increased in the fetal stage, and that in newborn rat liver was about 12 times that in 14-day fetal liver. In contrast, the aldolase A mRNA content decreased during gestation and that in newborn rat liver was about one-eighth of that in 14-day fetal liver. These observations suggest that the switch of aldolase isozyme expression in fetal liver is controlled by the levels of the respective mRNAs.
Fructose 1,6-diphosphate (FDP) aldolase and 2-keto-3-deoxy-D-gluconate (KDG) aldolase the two key enzymes of Embden-Meyerhof-Parnas (EMP) and the nonphosphorolytic Entner-Doudoroff (ED) pathways respectively, were identified in cell-free extracts of four Aspergillus oryzae strains grown on D-glucose as sole source of carbon. A. oryzae NRRL 3435 gave the highest enzymatic activity for the two enzymes and selected for further studies. Studies on the properties of the two key enzymes indicated that the optimum conditions for the activities of FDP aldolase and KDG aldolases occurred at pH 8.5, 45 degrees C and pH 8.0, 55 degrees C, respectively. Tris-acetate buffer and phosphate buffer showed the highest enzymatic activity for these two enzymes respectively. KDG aldolase was stable at 55 degrees C for 60 minutes however FDP aldolase was found to be less stable above 45 degrees C. On the other hand the two aldolases showed a high degree of stability towards frequent freezing and thawing. Dialysis of the extracts caused a decrease in the enzymatic activity of KDG aldolase, and an increase in FDP aldolase activity. The addition of ethylene diamine tetraacetate to the crude extracts caused an inhibition of KDG aldolase, whileas FDP aldolase was not affected. Addition of MnCl(2), CoSO(4), MgCl(2) and ZnSO(4) to the dialyzed extracts increased the activity of KDG aldolase by 67%, 54%, 61% and 37%, respectively. On the other hand the addition of some metal salts caused an inhibition of FDP aldolase. The results obtained indicate the absence of evidence for the involvement of sulfhydryl groups in the catalytic sites of the two aldolases.
Fructose-bisphosphate aldolase is a glycolytic enzyme whose activity increases in rice roots treated with gibberellin (GA). To investigate the relationship between aldolase and root growth, GA-induced root aldolase was characterized. GA3 promoted an increase in aldolase accumulation when 0.1 microM GA3 was added exogenously to rice roots. Aldolase accumulated abundantly in roots, especially in the apical region. To examine the effect of aldolase function on root growth, transgenic rice plants expressing antisense aldolase were constructed. Root growth of aldolase-antisense transgenic rice was repressed compared with that of the vector control transgenic rice. Although aldolase activity increased by 25% in vector control rice roots treated with 0.1 microM GA3, FBPA activity increased very little by 0.1 microM GA3 treatment in the root of aldolase-antisense transgenic rice. Furthermore, aldolase co-immunoprecipitated with antibodies against vacuolar H+ -ATPase in rice roots. In the root of OsCDPK13-antisense transgenic rice, aldolase did not accumulate even after treatment with GA3. These results suggest that the activation of glycolytic pathway function accelerates root growth and that GA3-induced root aldolase may be modulated through OsCDPK13. Aldolase physically associates with vacuolar H-ATPase in roots and may regulate the vacuolar H-ATPase mediated control of cell elongation that determines root length.
A sensitive sandwich-type enzyme immunoassay for brain-type isozyme of human aldolase C4 was developed using purified antibodies specific to the C subunit. The antibodies were raised in rabbits by injecting the purified aldolase C4, and purified by means of immunoaffinity chromatography on a column of aldolase C4-coupled Sepharose. The assay system consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and the same antibody Fab' fragments labelled with beta-D-galactosidase from Escherichia coli. The assay was highly sensitive and the minimum detection limit of aldolase C4 was 3 pg/tube. The assay was specific to the C subunit of aldolase (aldolase C). It cross-reacted about 60% with aldolase AC3, 30% with aldolase A2C2, and 4% with aldolase A3C, but showed no cross-reactivity with aldolase A4, the muscle-type isozyme. Coefficients of variation in within-run and between-run precision studies for serum aldolase C were less than or equal to 11%. Serum aldolase C levels in healthy adults of various ages (16-59 yr old) and both sexes ranged from 8.74-18.9 ng/ml. Immunoreactive aldolase C in the extracts of various human tissues was determined. It was distributed at high concentrations in the central nervous tissue and heart and at significant levels in liver, adrenal glands and testis. The assay of aldolase C in cerebrospinal fluid or serum by employing this sensitive immunoassay might be useful in the diagnosis of neurological disorders or acute myocardial damage.