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Cloning, sequencing, and chromosomal location of a putative class-II aldolase gene from Streptococcus pneumoniae.

The nucleotide sequence of a 1620-bp chromosomal fragment from Streptococcus pneumoniae, containing a putative class-II aldolase gene, has been determined. The N-terminal amino acid (aa) sequence of S. pneumoniae class-II aldolase protein allowed us to determine the initiation site for the putative aldolase gene, and a molecular weight of 31,274 Da was predicted for the protein, after removal of the N-terminal methionine. Northern hybridization and primer extension analysis showed a 1100-nucleotide transcript with a transcription start site located 43 or 42 bp upstream of the start codon. Southern hybridization studies indicated that the putative class-II aldolase gene was in the ApaI fragment 6, SmaI fragment 9, and SacII fragment 12 or 13 of the physical map of S. pneumoniae chromosome. Southern hybridization analysis and partial sequencing performed in another eight streptococcus species, belonging to six different phylogenetic groups, suggested that a class-II aldolase gene with a considerable DNA homology to that of the S. pneumoniae, could exist in these streptococcal species.

Amino Acid Sequence↗

Equilibrium partition studies of the interaction between aldolase and myofibrils.

The adsorption of aldolase to myofibrils derived from rabbit skeletal muscle has been investigated by partition equilibrium studies at pH 6.8, I = 0.158 M, and the results interpreted in terms of an intrinsic association constant of 410,000 M-1 for the interaction of four sites on aldolase with myofibrillar sites, there being one such site for every 10-12 heptameric repeat units of F-actin-tropomyosin-troponin thin filament. Involvement of the active site of the enzyme in the adsorption process is indicated by the fact that competitive inhibition of the phenomenon by phosphate may be accounted for by an intrinsic association constant of 400 M-1 for the aldolase-phosphate interaction, a value in good agreement with that describing phosphate inhibition of the enzymatic hydrolysis of fructose-1,6-bisphosphate under similar conditions. On the basis of these equilibrium constants plus the aldolase and thin filament contents of muscle, resting muscle is indicated as containing a significant proportion (25-30%) of aldolase in the bound form, with changes in the subcellular distribution of the enzyme being likely during exercise due to the increased concentrations of Ca2+ and fructose-1,6-bisphosphate that then prevail.

Animals↗

Recombinant anaerobic maize aldolase: overexpression, characterization, and metabolic implications.

Complementary DNA sequence of anaerobically induced cytoplasmic maize aldolase was expressed under control of the tac promoter sequence in Escherichia coli using the pKK223-3 plasmid as a vehicle. Levels of recombinant protein expressed exceeded 20 mg of soluble aldolase per liter of culture. The purified recombinant enzyme displayed the expected molecular weight and tetrameric subunit assembly on the basis of mobilities on denaturing electrophoretic gels and gel filtration, respectively. Sequencing of the NH2 terminus and amino acid composition analysis of the recombinant protein including COOH-terminal peptides agreed with the cDNA sequence. Partial kinetic characterization based on product inhibition studies was consistent with the ordered uni-bi reaction mechanism expected of aldolases. Turnover with respect to substrates Fru-1,6-P2 and Fru-1-P by the recombinant enzyme is the highest reported to date for class I aldolases. Fru-1,6-P2 cleavage rate by recombinant cytoplasmic maize enzyme is three times greater than that of the chloroplast enzyme. Fru-1-P cleavage is 8-fold greater than that of the rabbit liver isozyme and 20-fold greater than that of the rabbit muscle isozyme to which maize aldolase exhibits the greatest homology. The implications of such a high Fru-1-P turnover on carbohydrate utilization under anaerobiosis is discussed.

Amino Acid Sequence↗

Changes of aldolase A and B messenger RNA levels in rat liver during azo-dye-induced hepatocarcinogenesis.

The expression of aldolase A and B mRNAs during azo-dye-induced carcinogenesis in rat liver was examined. After feeding the dye for 18 weeks, the level of aldolase A mRNA increased to about 11 times that in a normal liver, with the concomitant decrease of aldolase B mRNA level to about 25% of that in a normal liver. These changes did not occur progressively during the carcinogenesis, but occurred as an additional phase after 4 week-feeding of the azo-dye. At this stage, the levels of aldolase A and B mRNAs were about 7 times and 45% of that in a normal liver, respectively. This biphasic pattern in the aldolase isozyme expression in the azo-dye-fed rat liver is discussed together with the kinetic data of the enzyme activity.

Animals↗

Expression of aldolase A messenger RNAs in human adult and foetal tissues and in hepatoma.

3 specific cDNA clones for human aldolase A were isolated from a human muscle library. One of them was subcloned in M 13 phage, then used as a probe to investigate the patterns and the levels of aldolase A mRNA in various human tissues. Two mRNA species differing in length were observed. The lighter one -1550 bases- was found specific to skeletal muscle; its amount increased during muscle development. The heavier aldolase A mRNA -1650 bases- accounted for foetal and ubiquitous presence of aldolase A isozyme. The resurgence of aldolase A in hepatomas occurred through this latter mRNA species.

Animals↗

Localization of aldolase C mRNA in brain cells.

The expression of aldolase C and aldolase A mRNA was assessed by Northern blot hybridization using RNAs purified from cultured rat and mouse brain neurons and astroglial cells. Neurons were found to contain about 4-fold more aldolase C mRNA and about twice as much aldolase A mRNA than astroglia. Analysis of the cellular localization of aldolase C mRNA by in situ hybridization to brain slices showed a predominantly neuronal labeling with an irregular distribution. A strong signal was observed in Purkinje cell somata and a weaker signal in subpopulations of neurons in cerebral cortex, striatum, hippocampus, hypothalamic nuclei and primary olfactory cortex.

Animals↗

Evidence for the spatial separation of the binding sites for substrate and for cytoskeletal proteins on the enzyme aldolase.

The effect of the proteolysis of aldolase on both the substrate specificity of the enzyme and binding capacity for actin have been studied. Carboxypeptidase A, trypsin, chymotrypsin and pepsin, all acted to cleave peptides from the C-terminal portion of the enzyme, resulting initially in a marked loss of activity towards fructose-1:6-bisphosphate (FBP), without impairment of activity towards fructose-1-phosphate (F1P). In some cases, however, further proteolysis caused reductions in activity with F1P as well. By correlating the size of the peptide fragments released by these enzymes with the known sequence of aldolase, evidence has been provided that cleavage of His-359 and/or Tyr-361 lead to the loss of FBP activity, while further cleavage of up to six amino acids begin to affect activity against F1P, as well. In regard to the ability of the proteolysed aldolase to bind to F-actin, it was evident from these studies that binding ability was not impaired in the initial stages of proteolysis referred to above, but was retained until the enzyme was extensively degraded. This differential behaviour of the active and binding sites on aldolase clearly establish their separate topographical localization. These results have been discussed in relation to the positioning of these separate sites on the enzyme, the nature of the interaction between aldolase and actin and the phenomenon of enzyme ambiquity in cells and tissues.

Animals↗

The effect of short- and long-term exercise on aldolase activity in muscles of CW-1 and C57/BL mice of various ages.

The effect of wheel running on the levels of fructose 1,6-bisphosphate aldolase A (EC 4.1.2.13) in striated muscles of young and old mice was compared. Short-term (6-10 weeks) and long-term (over 12 months) regimens were included in the study. The studies were conducted on the CW-1 outbred strain and on the C57/BL inbred strain of mice. It was shown that, in the short-term regimens, old animals of both strains showed either no increase (C57/BL) or a reduction (CW-1) in aldolase activity in hind leg muscles. On the other hand, young animals of both strains showed increases in aldolase activity of 10-20%. In the long-term regimen young and intermediate age animals showed 30-100% increases in aldolase activity in hind leg muscles over control sedentary animals. This adaptive capacity to exercise was not observed in old animals. However, long-term exercise regimen prevented the age-associated decline in aldolase activity found in sedentary animals.

Aging↗

Selective arylation of cysteine-237 of rabbit muscle aldolase with 4-chloro-7-nitrobenzofurazan.

At pH 7.0 and 25 degrees C, NBF-Cl (4-chloro-7-nitrobenzofurazan) reacts rapidly with rabbit muscle aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) to yield a product with an absorption maximum at 402 nm, which is shifted to 422 nm upon acid denaturation. The reaction involves arylation of a single cysteine residue per subunit of tetrameric aldolase, as shown by the molar absorptivity of NBF-aldolase and by titration of sulfhydryl groups of the enzyme with 5,5'-dithiobis(2-nitrobenzoic acid), DTNB. The site of arylation appears to be Cys-237, which is the cysteine residue that reacts most rapidly with DTNB. The site of arylation appears to be Cys-237, which is the cysteine residue that reacts most rapidly with DTNB, and which is not essential for aldolase activity. Arylation of the enzyme is 13-20-times more rapid than that of model compounds. The relatively high rate of arylation is not due to medium effects, to an anomalously low pKa of Cys-237, or to the presence of a binding site for NBF-Cl, and is tentatively assigned to acid-base catalysis by other functional groups in the vicinity of the reactive sulfhydryl group. The NBF-Cl reaction provides the most efficient means of titrating Cys-237 residues in rabbit muscle aldolase.

4-Chloro-7-nitrobenzofurazan↗

Inactivation of fructose-1,6-bisphosphate aldolase by cathepsin L. Stimulation by ATP.

Cathepsin L was capable of destroying rabbit muscle aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) activity towards the substrate fructose 1,6-bisphosphate. The rate of loss of activity towards this substrate was stimulated (approx. 2-fold) by physiological concentrations of ATP and to a lesser degree by GTP, CTP, UTP, ADP and cyclic AMP, while PPi and Pi decreased the rate of inactivation. Other proteinases (cathepsin B, cathepsin D, trypsin and chymotrypsin) also decreased aldolase activity toward fructose 1,6-bisphosphate more rapidly in the presence of ATP and more slowly in the presence of Pi. Cathepsin L, at higher concentrations, was capable of inactivating aldolase activity towards fructose 1-phosphate and extensively degrading the enzyme; these reactions were not affected by ATP and Pi. The thermostability of aldolase was also unaffected by these ligands. ATP and Pi had no effect on the rates of hydrolysis of other proteins (hemoglobin, bovine serum albumin, casein and azocasein) by cathepsin L. These data indicate that the effects of ATP and Pi are due to interactions of these ligands with aldolase that make the enzyme more vulnerable to limited but not extensive proteolysis; these ligands do not directly affect cathepsin L activity.

Adenosine Triphosphate↗

Modulation of phosphofructokinase action by macromolecular interactions. Quantitative analysis of the phosphofructokinase-aldolase-calmodulin system.

The simultaneous effect of calmodulin and aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) on the concentration-dependent behaviour of muscle phosphofructokinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) has been analysed by means of a covalently attached fluorescent probe, gel penetration experiments, and using a kinetic approach. We found that calmodulin-induced inactivation of phosphofructokinase is suspended by addition of an equimolar amount of aldolase. This effect was attributed to an apparent competition of calmodulin and aldolase for the dimeric forms of kinase. Moreover, the direct binding of aldolase to calmodulin has also been demonstrated, which resulted in a significant decrease in the kcat value of the enzyme. The quantitative analysis of these interactions in the system phosphofructokinase-calmodulin-aldolase is presented. A possible molecular model for the modulation of phosphofructokinase action by macromolecular interactions is envisaged.

Animals↗

An exploration of the binding site of aldolase using N-(omega-hydroxyalkyl) glycolamidobisphosphoric esters.

N-(omega-Hydroxyalkyl)glycolamidobisphosphoric esters (P-O-CH2-CO-NH-(CH2)n -O-P), which are analogues of the aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) substrate fructose 1,6-bisphosphate, were synthesized and used for probing its active site. These phosphate compounds competitively inhibited aldolase activity. The Ki value was lowest when the maximum distance between the phosphorus atoms of the bisphosphate was brought close to that of fructose 1,6-bisphosphate. The inhibitor constants, Ki, were compared to those of alkanediol monoglycolate bisphosphoric esters and alkanediol bisphosphate compounds, which were reported previously by Ogata et al. The values of Ki for the bisphosphate compounds containing an amide group, the amide bisphosphate compounds, were smaller than those for the bisphosphate compounds containing an ester group, the ester bisphosphate compounds, and those for alkanediol bisphosphates were the largest for the same distance between phosphorus atoms in these bisphosphates. The difference spectra of aldolase caused by binding of a saturating concentration of N-(omega-hydroxypropyl)glycolamidobisphosphoric ester resembled that of butanediol monoglycolate bisphosphoric ester. However, the effects of the amide bisphosphate compounds on the absorption spectrum of aldolase were smaller than those of the ester bisphosphate compounds for the same distance between phosphorus atoms in these bisphosphate compounds. These results suggest that the synthesized phosphate compounds bind to aldolase at the active site and the -CO-NH- group of the compounds might be held more tightly than the -CO-O- group by hydrogen bonds, presumably with the amino acid residues in the active site, such as Lys-146 or -229 and Asp-33 or Glu-187. On the other hand, the -CO-O- group might be more effective in changing the environment of the Trp-147 residue in the active site of this enzyme.

Animals↗

An exploration of the binding site of aldolase using alkyl glycolamido phosphoric esters and alkyl monoglycolate phosphoric esters.

Alkyl glycolamido phosphoric esters (P-O-CH2-CO-NH-(CH2)n-CH3) and alkyl monoglycolate phosphoric esters (P-O-CH2-CO-O-(CH2)n-CH3), which are analogs of the aldolase substrate fructose-1-phosphate, were synthesized and use for probing the active site of rabbit muscle aldolase. The inhibition constants (Ki) were affected by the length of the alkyl groups of these compounds and a maximum value of Ki was observed between the number of methylene groups 2 and 4, depending on the type of compound. In the previous investigation, N-(omega-hydroxyalkyl)-glycolamido bisphosphoric esters (P-O-CH2-CO-NH-(CH2)n-O-P) and alkanediol monoglyclolate bisphosphoric esters (P-O-CH2-CO-O-(CH2)n-O-P) have a minimum Ki value between the number of methylene groups 1 and 4. The difference spectra of aldolase caused by binding of alkyl glycoamido phosphoric esters or alkyl monophosphates resembled that of their analogous bisphosphoric esters, but the intensity of absorbance was smaller than that of the bisphosphoric ester analogs. These results suggest that rabbit muscle aldolase has two binding sites for the phosphate groups on the entrance end of the active site cavity, the singly wound beta-barrel of the parallel alpha/beta class structure. The distance between the phosphate binding site Lys-107 in the beta-sheet structure (c) and Arg-148 in the beta-sheet structure (d) may possibly be expanded or contracted by the forms of the bending structure of the biphosphate compounds. Also, the change of distance between the beta-sheet structure (c) and (d) containing Trp-147, may have an effect on the environment of the tryptophan and cause a change of the absorbance of aldolase especially at 295-299 nm. On the other hand, the synthetic monophosphate compounds bind at only one of the two phosphate binding sites and have very little effect on the absorbance of Trp-147, in a similar manner as orthophosphate. The alkyl groups of monophosphate may be repelled by the ionic amino acid side chains, Asp-33, Lys-146, Glu-187 and/or Lys-229 in the middle of the active site cavity. However, the end of the long alkyl group of some monophosphates may possibly contact the hydrophobic bottom of the active site cavity without effect on the environment of Trp-147.

Binding Sites↗

Fructose-bisphosphate aldolases: an evolutionary history.

Two mechanistically distinct forms of fructose-bisphosphate aldolase are known to exist. It has been assumed that the Class II (metallo) aldolases are evolutionary more primitive than their Class I (Schiff-base) analogs since the latter had only been found in eukaryotes. With the identification of prokaryotic Class I aldolases, we present here an alternative scheme of aldolase evolution. This scheme proposes that both aldolase classes are evolutionarily ancient and rationalizes the observed highly variable expression of both enzyme types in contemporary file forms.

Animals↗

Amplification of nuclear aldolase A in mouse cell mutants resistant to Hoechst 33342.

5-Bromodeoxyuridine (BrdU) induces a phenomenon similar to cellular senescence in mammalian cells. AT-binding ligands such as Hoechst 33258 synergistically potentiate the effect of BrdU. We isolated mouse FM3A cell mutants resistant to Hoechst 33342 and characterized two highly resistant mutants. Two-dimensional gel electrophoresis followed by peptides sequence tags revealed that nuclear aldolase A was markedly increased in both mutants. Western blot analysis confirmed that nuclear aldolase A was increased leaving cytosolic aldolase A unaltered. Its mRNA levels were also increased in the mutants. Enforced expression of aldolase A conferred resistance to Hoechst 33342 on wild-type cells. Taken together, nuclear aldolase A was shown to somehow protect the cytotoxic effect of Hoechst 33342.

Animals↗

Structure of the thermolabile mutant aldolase B, A149P: molecular basis of hereditary fructose intolerance.

Hereditary fructose intolerance (HFI) is a potentially lethal inborn error in metabolism caused by mutations in the aldolase B gene, which is critical for gluconeogenesis and fructose metabolism. The most common mutation, which accounts for 53% of HFI alleles identified worldwide, results in substitution of Pro for Ala at position 149. Structural and functional investigations of human aldolase B with the A149P substitution (AP-aldolase) have shown that the mutation leads to losses in thermal stability, quaternary structure, and activity. X-ray crystallography is used to reveal the structural basis of these perturbations. Crystals of AP-aldolase are grown at two temperatures (4 degrees C and 18 degrees C), and the structure solved to 3.0 angstroms resolution, using the wild-type structure as the phasing model. The structures reveal that the single residue substitution, A149P, causes molecular disorder around the site of mutation (residues 148-159), which is propagated to three adjacent beta-strand and loop regions (residues 110-129, 189-199, 235-242). Disorder in the 110-129-loop region, which comprises one subunit-subunit interface, provides an explanation for the disrupted quaternary structure and thermal instability. Greater structural perturbation, particularly at a Glu189-Arg148 salt bridge in the active-site architecture, is observed in the structure determined at 18 degrees C, which could explain the temperature-dependent loss in activity. The disorder revealed in these structures is far greater than that predicted by homology modeling and underscores the difficulties in predicting perturbations of protein structure and function by homology modeling alone. The AP-aldolase structure reveals the molecular basis of a hereditary disease and represents one of only a few structures known for mutant proteins at the root of the thousands of other inherited disorders.

Binding Sites↗

LPS increases hepatic HIF-1alpha protein and expression of the HIF-1-dependent gene aldolase A in rats.

BACKGROUND: Cellular adaptation to hypoxia is mediated in part by the transcription factor hypoxia-inducible factor 1 (HIF-1). Accumulating data suggest that pro-inflammatory mediators can up-regulate HIF-1alpha protein expression and HIF-1 DNA-binding activity in the absence of hypoxia. Accordingly, we investigated HIF-1 mediated signaling in endotoxemic rats. MATERIALS AND METHODS: We studied three groups of male Sprague Dawley rats. Controls (N = 5) were injected i.p. with saline. Endotoxemic rats (N = 9) received a sublethal dose of lipopolysaccaride (Escherichia coli; 5 mg/kg, i.p.). A third group of rats (N = 5) received the HIF-1 stabilizing agent CoCl(2) (14 mg/kg, i.p.) at T = 0 h and T = 16 h. At T = 18 h, liver microvascular perfusion was measured using laser Doppler flowmetry and hepatic tissue samples were obtained. RNA was isolated and mRNA levels of the HIF-1 dependent genes aldolase A and vascular endothelial growth factor (VEGF) were determined using quantitative real-time RT-PCR. HIF-1alpha content was estimated by immunoprecipitation followed by Western blotting. RESULTS: HIF-1alpha increased in hepatic tissue after treatment with LPS or CoCl(2). LPS markedly increased hepatic expression of aldolase A, but failed to alter expression of VEGF. CoCl(2) increased aldolase A and VEGF mRNA expression. Although hepatic microvascular perfusion was comparable in saline- and LPS-treated rats, hepatic microvascular blood flow and aldolase A expression were significantly inversely correlated among endotoxemic rats (r = 0.773; P = 0.003). CONCLUSIONS: Increased expression of aldolase A in endotoxemic rats is mediated by both hypoxia-dependent and hypoxia-independent mechanisms.

Analysis of Variance↗

Purkinje cell expression of the mouse aldolase C gene in transgenic mice is directed by an upstream regulatory element.

We have sought to understand the regulation of the expression pattern of aldolase C (Zebrin II) in cerebellar Purkinje cells. Normally, aldolase C is expressed in a series of sagittal stripes of Purkinje cells interrupted by stripes of little or no expression. Genomic aldolase C:LacZ fusion genes with 1.8 kb of sequence 5' to the transcription start site drive CNS expression of LacZ only in astrocytes and cells of the pia mater. If the 5' portion of the transgene is extended to a full 5.0 kb, expression is reliably observed in Purkinje cells, yet none of the astrocyte expression is lost. We broke the additional 3.0 kb into 1.0 kb fragments and tested each for Purkinje cell enhancer activity when appended to the original 1.8 kb construct. We show that the 886 bp region from nucleotide -2796 to -3682 (relative to the start of transcription) contains virtually all of the Purkinje cell enhancer activity. However, neither the full 5.0 kb nor the 886 bp region directed a striped expression pattern, as is seen for the endogenous gene. Taken together, our study localizes a Purkinje cell enhancer to a small 5' region of the aldolase C gene and illustrates that the element(s) responsible for the normal anatomically complex pattern of aldolase C expression are separate from those conferring cell-type specificity. The relationship of these findings to previous work in other laboratories is discussed.

Animals↗