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The temperature dependence of activity and structure for the most prevalent mutant aldolase B associated with hereditary fructose intolerance.

Hereditary fructose intolerance (HFI) is an autosomal recessive disorder in humans which is caused by mutations in the aldolase B gene. The most common HFI allele encodes an enzyme with an A149P substitution (AP-aldolase). A lysis method suitable for aggregation-prone proteins overexpressed in bacteria was developed. The enzyme's structure and function is investigated as a function of temperature. Near-UV CD shows a qualitative difference in tertiary structure, whereas far-UV CD shows no difference in overall secondary structure, although both show increased temperature sensitivity for AP-aldolase compared to that seen with wild-type aldolase B. AP-aldolase exists as a dimer at all temperatures tested, unlike the tetrameric wild-type enzyme, thus providing a possible explanation for the loss in thermostability. AP-aldolase has sixfold lower activity than wild type at 10 degrees C, which decreases substantially at higher temperature. In addition to disruptions at the catalytic center, the kinetic constants toward different substrates suggest that there is a disruption at the C1-phosphate-binding site, which is not sensitive to temperature. The implications of these structural alterations are discussed with regard to the HFI disease.

Binding Sites↗

The complex of band 3 protein of the human erythrocyte membrane and glyceraldehyde-3-phosphate dehydrogenase: stoichiometry and competition by aldolase.

The cytoplasmic domain of band 3, the main intrinsic protein of the erythrocyte membrane, possesses binding sites for a variety of other proteins of the membrane and the cytoplasm, including the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and aldolase. We have studied the stoichiometry of the complexes of human band 3 protein and GAPDH and the competition by aldolase for the binding sites. In addition, we have tried to verify the existence of mixed band 3/GAPDH/aldolase complexes, which could represent the nucleus of a putative glycolytic multienzyme complex on the erythrocyte membrane. The technique applied was analytical ultracentrifugation, in particular sedimentation equilibrium analysis, on mixtures of detergent-solubilized band 3 and dye-labelled GAPDH, in part of the experiments supplemented by aldolase. The results obtained were analogous to those reported for the binding of hemoglobin, aldolase and band 4.1 to band 3: (1) the predominant or even sole band 3 oligomer forming the binding site is the tetramer. (2) The band 3 tetramer can bind up to four tetramers of GAPDH. (3) The band 3/GAPDH complexes are unstable. (4) Artificially stabilized band 3 dimers also represent GAPDH binding sites. In addition it was found that aldolase competes with GAPDH for binding to the band 3 tetramer, and that ternary complexes of band 3 tetramers, GAPDH and aldolase do exist.

Anion Exchange Protein 1, Erythrocyte↗

Fluorescence analysis of aldolase dissociation from the N-terminal of the cytoplasmic domain of band 3 induced by lanthanide.

The cytoplasmic domain of band 3 (CDB3) offers binding sites for several glycolytic enzymes and regulates the glycolysis of erythrocyte. The interaction between recombinant (His)(6)-tagged CDB3 and aldolase, one of the key enzymes that participated in erythrocyte glycolysis, was investigated in the presence of lanthanide. The results indicate that trace lanthanide blocks the inhibition of CDB3-(His)(6) to aldolase and leads to enhancement of aldolase activity. In agreement with activity studies, fluorescence spectra reveal that 4 microM lanthanum ions induce the complete dissociation of aldolase from the N-terminal of CDB3-(His)(6). Interestingly, the synchronous scanning fluorescence spectra of proteins in the presence of various concentrations of lanthanum ions suggest that the conformational change of CDB3-(His)(6) is significantly attributed to the alteration of tryptophan cluster microenvironment, while the aldolase conformation change is mainly derived from tyrosine microenvironment changes. Based on the observation that lanthanide ions induce the dissociation of aldolase from CDB3-(His)(6), it is suggested that the existence of trace lanthanide may affect the glycolysis of erythrocyte.

Anion Exchange Protein 1, Erythrocyte↗

Extreme X-ray sensitive modification of type I aldolases by blue dye ligand chromatography.

Aldolases purified by Blue dye ligand chromatography from a variety of vertebrate sources crystallize at room temperature in a habit similar to the monoclinic form of rabbit skeletal muscle aldolase. Crystals of aldolases thus purified including rabbit muscle aldolase are extremely sensitive to X-ray (Cu K alpha) radiation and shatter after short exposure to X-ray radiation (less than 5 min.). Crystals of aldolases purified by other techniques possess demonstrable diffraction patterns and are stable in the X-ray beam with lifetimes of the order of days. No clear distinction could be made on the basis of different biochemical assays between aldolases purified by Blue dye chromatography and those purified by other techniques.

Animals↗

Brownian dynamics simulations of aldolase binding glyceraldehyde 3-phosphate dehydrogenase and the possibility of substrate channeling.

Brownian dynamics (BD) simulations test for channeling of the substrate, glyceraldehyde 3-phosphate (GAP), as it passes between the enzymes fructose-1,6-bisphosphate aldolase (aldolase) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). First, BD simulations determined the favorable complexes between aldolase and GAPDH; two adjacent subunits of GAPDH form salt bridges with two subunits of aldolase. These intermolecular contacts provide a strong electrostatic interaction between the enzymes. Second, BD simulates GAP moving out of the active site of the A or D aldolase subunit and entering any of the four active sites of GAPDH. The efficiency of transfer is determined as the relative number of BD trajectories that reached any active site of GAPDH. The distribution functions of the transfer time were calculated based on the duration of successful trajectories. BD simulations of the GAP binding from solution to aldolase/GAPDH complex were compared to the channeling simulations. The efficiency of transfer of GAP within an aldolase/GAPDH complex was 2 to 3% compared to 1.3% when GAP was binding to GAPDH from solution. There is a preference for GAP channeling between aldolase and GAPDH when compared to binding from solution. However, this preference is not large enough to be considered as a theoretical proof of channeling between these proteins.

Binding Sites↗

Evidence that a mitogen-inducible prolactin-immunoreactive protein in rat spleen lymphocytes is aldolase A.

This study characterizes several proteins in rat spleen lymphocyte lysates and conditioned medium that are recognized by antiserum to purified rat pituitary prolactin (PRL). One of these proteins, rat prolactin-immunoreactive protein (rPIP-43), has a relative molecular mass (Mr) of 43,000 and is strongly induced by mitogenic stimulation in spleen lymphocytes. A constitutively expressed protein of this size also was detected in the IM-9 human B lymphoblastoid cell line and the Nb2 rat T lymphoma cell line. The N-terminal amino acid sequence of rPIP-43 in spleen lymphocyte lysate was analysed and found to be identical with 25 residues at the N-terminus of the glycolytic enzyme aldolase A. In further experiments, the rPRL antiserum was evaluated for cross-reactivity with an aldolase A preparation and recognized a Mr 43,000 protein in rabbit muscle. Preabsorption of rPRL antiserum with rPRL was found to greatly decrease the intensity of staining of rPRL, aldolase A and rPIP-43. Preabsorption of antiserum with aldolase A had a similar, but less pronounced effect, with the aldolase A band and rPIP-43 being stained less intensely, while there was no effect on the intensity of staining of purified rPRL. Thus, data indicate that rPIP-43 is not a structural variant of PRL, but appears to be a different protein. These results have implications for the use of PRL antiserum to detect PRL in biological samples insofar as aldolase A is a ubiquitously expressed protein.

Amino Acid Sequence↗

Fructose 1,6-bisphosphate aldolase activity in leaves of a rice mutant selected for enhanced lysine.

Unknown proteins isolated from mutant tissues of rice (Oryza sativa L.) recovered from inhibitor selections were subsequently peptide microsequenced. Database searches putatively identified one peptide as fructose 1,6-bisphosphate aldolase (EC 4.1.2.13). Tissues of mutant rice, PI564784, and wild type (cv Calrose 76) tissues were evaluated for aldolase activity. Total enzyme activities were slightly lower in the mutant than the control but the differences were not significant. Although the mutant phenotype is for enhanced lysine and protein, we ascribe the small aldolase differences to physiological adjustments, rather than to DNA modifications of the aldolase gene(s). Homologies of rice peptides with aldolases from a range of species, as well as rice cell culture expressed sequence tags (ESTs) are presented. Some amino acids sequences are highly conserved. The mutant phenotype expressing stress proteins is not likely to be defined by a change in rice aldolases.

Amino Acid Sequence↗

Cloning and unusual expression profile of the aldolase B gene from Atlantic salmon.

A full-length clone of the aldolase B gene has been isolated from a cDNA library constructed from liver of Atlantic salmon (Salmo salar). Sequencing showed that the clone encodes a typical aldolase B, possessing a number of amino acid residues which are seen in aldolase B, but not in other aldolase isoforms. RT-PCR analysis showed that the gene is expressed in liver, kidney and intestine as expected. However, in contrast to mammalian and avian aldolase B, expression was also found in a number of other tissues. Levels of aldolase B mRNA in liver and kidney were not significantly altered during smoltification, the transformation of freshwater-dwelling salmon (parr) into saltwater-adapted salmon (smolts).

Amino Acid Sequence↗

Glucose metabolism in Escherichia coli and the effect of increased amount of aldolase.

We present a comparative study of Escherichia coli with normal and increased amounts of fructose-1,6-bisphosphate aldolase. Most experiments employed a resting cell system involving a high cell density (so as to obtain the soluble pool by direct extraction) and anaerobic incubation in the presence of chloramphenicol. Glucose use is linear with time with a rate ca. half of that in growth, fermentation is almost quantitative, and metabolite concentrations reach a quasi steady state. Increased amount of aldolase had little effect on glucose flux; fructose-1,6-P2 concentration decreased by ca. one-third, and the extent of equilibration of its two halves, measured by a dismutation procedure on samples taken during metabolism of [6-14C]glucose, increased from 0.33 [(cpm in C1-3)/(cpm in C1-6)] to 0.43. Using the simplest model, that increased amount of aldolase does not perturb net flux or later metabolites, together with the steady-state rate equations for aldolase and triose-P isomerase, we show that the results with resting cells fit with the extra enzyme being fully active, and do not necessitate special assumptions concerning a glycolytic complex, metabolite compartmentation, or secondary mechanisms assuring high metabolite concentration. However, the fit does require that the measured Vmax values substantially underestimate the actual ones. Calculation also shows that the forms of the predicted curves--and hence the fit with experimental data--of fructose-1,6-P2 concentration and labeling as a function of the amount of aldolase are highly dependent on glyceraldehyde-3-P concentration but independent of the kinetic parameters of aldolase.

Anaerobiosis↗

Liver aldolase anomeric specificity.

Stopped-flow kinetic studies of liver aldolase and of mixed liver-muscle aldolase catalyzed reactions of fructose 1,6-bisphosphate (FBP) have been carried out and interpreted by computer simulation. These experiments indicate no utilization or binding of the alpha anomer by the liver enzyme unlike the findings for either the muscle aldolase which binds the alpha anomer nonproductively or the yeast aldolase which catalyzes its cleavage. Both beta-fructose 1,6-bisphosphate and its acyclic keto form may serve as substrates, necessitating the spontaneous anomerization of the alpha anomer before its utilization. Thus, liver aldolase cleaves 100% of the substrate present in the millisecond time scale because of the inability to bind alpha-FBP, allowing rapid spontaneous anomerization. This result fulfills earlier predictions of the differing specificities and substrate binding properties for aldolases from yeast, muscle, and liver.

Animals↗

Quaternary structure of aldolase leads to differences in its folding and unfolding intermediates.

Pulsed hydrogen exchange mass spectrometry has been used to investigate folding of rabbit muscle aldolase, an alpha/beta-barrel protein exhibiting the classic TIM structure. Aldolase unfolded in GdHCl refolded as the denaturant concentration was reduced by dialysis. Samples withdrawn during dialysis were pulse-labeled with deuterium to identify unfolded regions in structural forms highly populated during the folding process. Intact, labeled aldolase was digested into fragments, which were analyzed by HPLC electrospray ionization mass spectrometry to detect the H/D exchange along the aldolase backbone. For some concentrations of GdHCl, bimodal distributions of deuterium were found for most peptic fragments, indicating that regions represented by these fragments were either unfolded or folded in the intact polypeptide prior to labeling. The extent of folding was determined from these mass spectra, as well as by CD (220 nm) and enzymatic activity. These results show that folding to the active form involves three domains and two intermediates. Approximately 110 residues fold to highly compact forms in each step. These results also show that each folding domain includes widely separated regions of the backbone. When compared with the results of a previous study of aldolase unfolding, these results show that the folding and unfolding domains include most of the same residues. However, three short segments change domains depending on whether the process is folding or unfolding. These changes are attributed to the very stable quaternary structure of rabbit muscle aldolase.

Animals↗

Differential distribution of aldolase A and C in the human central nervous system.

We have analyzed the distribution of aldolase A and C mRNAs and proteins in various areas of the human brain using Northern blot analyses and immunohistochemistry. Aldolase A mRNA expression was higher than aldolase C mRNA expression in all areas of the brain examined. Aldolase C mRNA expression was highest in the cerebellum. Aldolase C protein was present in well-delimited regions of the CNS, and was distributed in stripes in the Purkinje cell layer of the cerebellum, in the inferior olives and in the sensory neurons of the posterior horn of the spinal cord. The novel finding of aldolase C in well-delimited cell compartments of the human cerebellum and in several other areas of the CNS lends weight to the hypothesis that this protein exerts other functions (e.g. sensory transmission) besides those characteristic of a glycolytic enzyme.

Afferent Pathways↗

Artificial aldolases from peptide dendrimer combinatorial libraries.

Peptide dendrimers were investigated as synthetic models for aldolase enzymes. Combinatorial libraries were prepared with aldolase active residues such as lysine and proline placed at the dendrimer core or near the surface. On-bead selection for aldolase activity was carried out using the dye-labelled 1,3-diketone 1a, suitable for covalent trapping of enamine-reactive side-chains, and the fluorogenic enolization probe 6. Aldolase dendrimers catalyzed the aldol reaction of acetone, dihydroxyacetone and cyclohexanone with nitrobenzaldehyde. Much like enzymes, the dendrimers exhibited strong aldolase activity in aqueous medium, but were also active in organic solvent. Dendrimer-catalyzed aldol reactions reached complete conversion in 3 h at 25 degrees C with 1 mol% catalyst and gave aldol products with up to 65% ee. A positive dendritic effect in catalysis was observed with both lysine and proline based aldolase dendrimer catalysts.

Amino Acids↗

Purification and characterization of two fructose diphosphate aldolases from Escherichia coli (Crookes' strain).

Two fructose diphosphate aldolases (EC 4.1.2.13) were detected in extracts of Escherichia coli (Crookes' strain) grown on pyruvate or lactate. The two enzymes can be resolved by chromatography on DEAE-cellulose at pH7.5, or by gel filtration on Sephadex G-200, and both have been obtained in a pure state. One is a typical bacterial aldolase (class II) in that it is strongly inhibited by metal-chelating agents and is reactivated by bivalent metal ions, e.g. Ca(2+), Zn(2+). It is a dimer with a molecular weight of approx. 70000, and the K(m) value for fructose diphosphate is about 0.85mm. The other aldolase is not dependent on metal ions for its activity, but is inhibited by reduction with NaBH(4) in the presence of substrate. The K(m) value for fructose diphosphate is about 20mum (although the Lineweaver-Burk plot is not linear) and the enzyme is probably a tetramer with molecular weight approx. 140000. It has been crystallized. On the basis of these properties it is tentatively assigned to class I. The appearance of a class I aldolase in bacteria was unexpected, and its synthesis in E. coli is apparently favoured by conditions of gluconeogenesis. Only aldolase of class II was found in E. coli that had been grown on glucose. The significance of these results for the evolution of fructose diphosphate aldolases is briefly discussed.

Amino Acids↗

Novel kinetic and structural properties of the class-I D-fructose 1,6-bisphosphate aldolase from Escherichia coli (Crookes' strain).

Investigation of aldolase 1, the class-I D-fructose 1,6-bisphosphate aldolase (EC4.1.2.13) from Escherichia coli (Crookes' strain), showed it to have unusual kinetic and structural properties. The enzyme appeared to be larger than was previously supposed and may be a decamer with a mol. wt. of approx. 340000. Its fructose 1,6-bisphosphate-cleavage activity was unaffected by these compounds. The enhancement exhibited a strong dependence on pH. These novel kinetic properties do not seem to be shared by any other fructose 1,6-bisphosphate aldolase, but recall the activation by polycarboxylic acids of the deoxyribose 3-phosphate aldolases from some other organisms. In view of its unusual properties, it is unlikely that aldolase 1 from E. coli is closely related to the class-1 aldolases that have been detected in several other prokaryotes, or to the typical class-1 enzymes from eukaryotes.

Amino Acids↗

Extended amino acid sequences around the active-site lysine residue of class-I fructose 1,6-bisphosphate aldolases from rabbit muscle, sturgeon muscle, trout muscle and ox liver.

1. Amino acid sequences covering the region between residues 173 and 248 [adopting the numbering system proposed by Lai, Nakai & Chang (1974) Science 183, 1204-1206] were derived for trout (Salmo trutta) muscle aldolase and for ox liver aldolase. A comparable sequence was derived for residues 180-248 of sturgeon (Acipenser transmontanus) muscle aldolase. The close homology with the rabbit muscle enzyme was used to align the peptides of the other aldolases from which the sequences were derived. The results also allowed a partial sequence for the N-terminal 39 residues for the ox liver enzyme to be deduced. 2. In the light of the strong homology evinced for these enzymes, a re-investigation of the amino acid sequence of rabbit muscle aldolase between residues 181 and 185 was undertaken. This indicated the presence of a hitherto unsuspected -Ile-Val-sequence between residues 181 and 182 and the need to invert the sequence -Glu-Val- to -Val-Glx- at positions 184 and 185. 3. Comparison of the available amino acid sequences of these enzymes suggested an early evolutionary divergence of the genes for muscle and liver aldolases. It was also consistent with other evidence that the central region of the primary structure of these enzymes (which includes the active-site lysine-227) forms part of a conserved folding domain in the protein subunit. 4. Detailed evidence for the amino acid sequences proposed has been deposited as Suy Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.

Amino Acid Sequence↗

Binding of aldolase to actin-containing filaments. Evidence of interaction with the regulatory proteins of skeletal muscle.

The interactions of aldolase with regulatory proteins of rabbit skeletal muscle were investigated by moving-boundary electrophoresis. A salt-dependent interaction of troponin, tropomyosin and the tropomyosin-troponin complex with aldolase was detected, the tropomyosin-troponin complex displaying a greater affinity for the enzyme than did either regulatory protein alone. The results indicate that aldolase possesses multiple binding sites (three or more) for these muscle proteins. Quantitative studies of the binding of aldolase to actin-containing filaments showed the interaction to be influenced markedly by the presence of these muscle regulatory proteins on the filaments. In imidazole/HCl buffer, I 0.088, pH 6.8, aldolase binds to F-actin with an affinity constant of 2 x 10(5) M-1 and a stoicheiometry of one tetrameric aldolase molecule per 14 monomeric actin units. Use of F-actin-tropomyosin as adsorbent results in a doubling of the stoicheiometry without significant change in the intrinsic association constant. With F-actin-tropomyosin-troponin a lower binding constant (6 x 10(4) M-1) but even greater stoicheiometry (4:14 actin units) are observed. The presence of Ca2+ (0.1 mM) decreases this stoicheiometry to 3:14 without affecting significantly the magnitude of the intrinsic binding constant.

Actins↗

Interaction of aldolase with actin-containing filaments. Structural studies.

Electron micrographs of the paracrystals formed when fructose bisphosphate aldolase (EC 4.1.2.13) is added to actin-containing filaments were analysed by computer methods so that ultrastructural changes could be correlated with the various stoicheiometries of binding determined in the preceding paper [Walsh, Winzor, Clarke, Masters & Morton (1980) Biochem. J. 186, 89-98]. Paracrystals formed with aldolase and either F-actin or F-actin-tropomyosin have a single light transverse band every 38 nm, which is due to aldolase molecules cross-linking the filaments. In contrast, the paracrystals formed between aldolase and F-actin-tropomyosin-troponin filaments show two transverse bands every 38 nm: a major band, interpreted as aldolase binding to troponin, and a minor band, interpreted as aldolase cross-linking the filaments. The intensity of the minor band varies with Ca2+ concentration, being greatest when the Ca2+ concentration is low. A model for the different paracrystal structures which relates the various patterns and binding stoicheiometries to structural changes in the actin-containing filaments is proposed.

Actins↗