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PubMed2002

Transaldolase exhibits a protective role against menadione toxicity in Xanthomonas campestris pv. phaseoli.

A talA gene encoded transaldolase, a rate-limiting enzyme in the non-oxidative branch of the pentose-phosphate pathway, was cloned from Xanthomonas campestris pv. phaseoli. talA located in a region of the bacterial genome rich in genes involved in oxidative stress protection and regulation. TalA from X. campestris pv. phaseoli showed a high degree of homology to many previously reported transaldolases from both prokaryotic and eukaryotic sources. The expression of X. campestris pv. phaseoli talA was high at log-phase of growth, then declined at stationary phase, and could not be induced by oxidants. A talA mutant constructed by insertional inactivation did not possess any detectable transaldolase activity. Lack of a functional talA gene did not affect bacterial growth in a rich medium containing glucose or sucrose as a carbon source. However, the talA knockout mutant showed increased sensitivity to the superoxide generator menadione, but not to other oxidants. This increased menadione sensitivity phenotype could be complemented by expression of talA in a plasmid vector. The data demonstrated a novel and essential role of transaldolase in protection against menadione toxicity in X. campestris.

Catalase↗
PubMed1998

Cloning and chromosomal localization of a paralog and a mouse homolog of the human transaldolase gene.

A sequence homologous to the transaldolase gene (TALDO) was identified in a polymorphic cosmid DNA mapped on human chromosome 11p15 by exon trapping with pSPL3. Analysis of lambda clones contiguous to the cosmid clone showed that the related gene (TALDOR) consists of 8 exons spanning approximately 19kb from the translation start site to the polyadenylation signal. The exon sequence of TALDOR was almost identical with that of TALDO localized on 1p33-34. 1, but its exons corresponding to exons 4 and 5 of TALDO were found to be split by 4 introns in TALDOR. To examine the evolutionary conservation of two genes for transaldolase, we have isolated the cDNA for its mouse homolog and determined the nucleotide sequence covering the complete coding region. Fluorescence in situ hybridization using the cDNA as a probe showed that the mouse transaldolase gene (Taldo) is localized on chromosome 7 F3-F4 as a single copy gene. This chromosomal region is known to be syntenic to human chromosome 11p15 rather than to 1p33-p34.1, suggesting that TALDOR is the ancestral form. The existence of TALDOR implies a duplication of the mammalian transaldolase gene after divergence of rodent and primate.

Amino Acid Sequence↗
PubMed2001

Transaldolase deficiency: liver cirrhosis associated with a new inborn error in the pentose phosphate pathway.

This article describes the first patient with a deficiency of transaldolase (TALDO1 [E.C.2.2.1.2]). Clinically, the patient presented with liver cirrhosis and hepatosplenomegaly during early infancy. In urine and plasma, elevated concentrations of ribitol, D-arabitol, and erythritol were found. By incubating the patient's lymphoblasts and erythrocytes with ribose-5-phosphate and subsequently analyzing phosphate sugar metabolites, we discovered a deficiency of transaldolase. Sequence analysis of the transaldolase gene from this patient showed a homozygous deletion of 3 bp. This deletion results in absence of serine at position 171 of the transaldolase protein. This amino acid is invariable between species and is located in a conserved region, indicating its importance for enzyme activity. The detection of this new inborn error of pentose metabolism has implications for the diagnostic workup of liver problems of unknown etiology.

Amino Acid Sequence↗
PubMed2002

Crystal structure of decameric fructose-6-phosphate aldolase from Escherichia coli reveals inter-subunit helix swapping as a structural basis for assembly differences in the transaldolase family.

Fructose-6-phosphate aldolase from Escherichia coli is a member of a small enzyme subfamily (MipB/TalC family) that belongs to the class I aldolases. The three-dimensional structure of this enzyme has been determined at 1.93 A resolution by single isomorphous replacement and tenfold non-crystallographic symmetry averaging and refined to an R-factor of 19.9% (R(free) 21.3%). The subunit folds into an alpha/beta barrel, with the catalytic lysine residue on barrel strand beta 4. It is very similar in overall structure to that of bacterial and mammalian transaldolases, although more compact due to extensive deletions of additional secondary structural elements. The enzyme forms a decamer of identical subunits with point group symmetry 52. Five subunits are arranged as a pentamer, and two ring-like pentamers pack like a doughnut to form the decamer. A major interaction within the pentamer is through the C-terminal helix from one monomer, which runs across the active site of the neighbouring subunit. In classical transaldolases, this helix folds back and covers the active site of the same subunit and is involved in dimer formation. The inter-subunit helix swapping appears to be a major determinant for the formation of pentamers rather than dimers while at the same time preserving importing interactions of this helix with the active site of the enzyme. The active site lysine residue is covalently modified, by forming a carbinolamine with glyceraldehyde from the crystallisation mixture. The catalytic machinery is very similar to that of transaldolase, which together with the overall structural similarity suggests that enzymes of the MipB/TALC subfamily are evolutionary related to the transaldolase family.

Aldehyde-Lyases↗
PubMed1996

Inhibition of the catalytic activity of human transaldolase by antibodies and site-directed mutagenesis.

Transaldolase is a key enzyme of the pentose phosphate pathway. While antibody (Ab) 169, directed against the N-terminal 139 residues of human transaldolase (TAL-H), had no effect on enzyme activity, Ab 12484 raised against full length and functional recombinant TAL-H inhibited catalytic activity. This tentatively mapped the catalytic site to the C-terminal 140-336 amino acid portion of TAL-H. Dihydroxyacetone transfer reactions catalyzed by transaldolase depend on Schiff base formation by a lysine residue. Replacement of lysine-142 by glutamine using site-directed mutagenesis resulted in a complete loss of enzyme activity, suggesting that lysine-142 is essential for the catalytic activity of TAL-H.

Amino Acid Sequence↗
PubMed2000

The three-dimensional structure of human transaldolase.

The crystal structure of human transaldolase has been determined to 2.45 A resolution. The enzyme folds into an alpha/beta barrel structure and is thus similar in structure to other class I aldolases. Structure-based sequence alignment of available sequences of the transaldolase subfamily reveals that eight active site residues are invariant in the whole subfamily. Other invariant residues are mainly involved in the formation of the hydrophobic core of the enzyme. Noteworthy is a hydrophobic cluster consisting of five invariant residues. Human transaldolase has been implicated as an autoantigen in multiple sclerosis and four immunodominant peptide segments are located at the surface of the enzyme, accessible to autoantibodies.

Amino Acid Sequence↗
PubMed2000

Fructose-6-phosphate aldolase is a novel class I aldolase from Escherichia coli and is related to a novel group of bacterial transaldolases.

We have cloned an open reading frame from the Escherichia coli K-12 chromosome that had been assumed earlier to be a transaldolase or a transaldolase-related protein, termed MipB. Here we show that instead a novel enzyme activity, fructose-6-phosphate aldolase, is encoded by this open reading frame, which is the first report of an enzyme that catalyzes an aldol cleavage of fructose 6-phosphate from any organism. We propose the name FSA (for fructose-six phosphate aldolase; gene name fsa). The recombinant protein was purified to apparent homogeneity by anion exchange and gel permeation chromatography with a yield of 40 mg of protein from 1 liter of culture. By using electrospray tandem mass spectroscopy, a molecular weight of 22,998 per subunit was determined. From gel filtration a size of 257,000 (+/- 20,000) was calculated. The enzyme most likely forms either a decamer or dodecamer of identical subunits. The purified enzyme displayed a V(max) of 7 units mg(-)1 of protein for fructose 6-phosphate cleavage (at 30 degrees C, pH 8.5 in 50 mm glycylglycine buffer). For the aldolization reaction a V(max) of 45 units mg(-)1 of protein was found; K(m) values for the substrates were 9 mm for fructose 6-phosphate, 35 mm for dihydroxyacetone, and 0.8 mm for glyceraldehyde 3-phosphate. FSA did not utilize fructose, fructose 1-phosphate, fructose 1,6-bisphosphate, or dihydroxyacetone phosphate. FSA is not inhibited by EDTA which points to a metal-independent mode of action. The lysine 85 residue is essential for its action as its exchange to arginine (K85R) resulted in complete loss of activity in line with the assumption that the reaction mechanism involves a Schiff base formation through this lysine residue (class I aldolase). Another fsa-related gene, talC of Escherichia coli, was shown to also encode fructose-6-phosphate aldolase activity and not a transaldolase as proposed earlier.

Aldehyde-Lyases↗
PubMed1995

Transaldolase B of Escherichia coli K-12: cloning of its gene, talB, and characterization of the enzyme from recombinant strains.

A previously recognized open reading frame (T. Yura, H. Mori, H. Nagai, T. Nagata, A. Ishihama, N. Fujita, K. Isono, K. Mizobuchi, and A. Nakata, Nucleic Acids Res. 20:3305-3308) from the 0.2-min region of the Escherichia coli K-12 chromosome is shown to encode a functional transaldolase activity. After cloning of the gene onto high-copy-number vectors, transaldolase B (D-sedoheptulose-7-phosphate:D-glyceraldehyde-3-phosphate dihydroxyacetone transferase; EC 2.2.1.2) was overexpressed up to 12.7 U mg of protein-1 compared with less than 0.1 U mg of protein-1 in wild-type homogenates. The enzyme was purified from recombinant E. coli K-12 cells by successive ammonium sulfate precipitations (45 to 80% and subsequently 55 to 70%) and two anion-exchange chromatography steps (Q-Sepharose FF, Fractogel EMD-DEAE tentacle column; yield, 130 mg of protein from 12 g of cell wet weight) and afforded an apparently homogeneous protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a subunit size of 35,000 +/- 1,000 Da. As the enzyme had a molecular mass of 70,000 Da by gel filtration, transaldolase B is likely to form a homodimer. N-terminal amino acid sequencing of the protein verified its identity with the product of the cloned gene talB. The specific activity of the purified enzyme determined at 30 degrees C with the substrates fructose-6-phosphate (donor of C3 compound) and erythrose-4-phosphate (acceptor) at an optimal pH (50 mM glycylglycine [pH 8.5]) was 60 U mg-1.Km values for the substrates fructose-6-phosphate and erythrose-4-phosphate were determined at 1,200 and 90 microM, respectively. Kinetic constants for the other two physiological reactants, D,L-glyceraldehyde 3-phosphate (Km, 38 microM; relative activity [V(rel)], 8%) and sedoheptulose-7-phosphate (K(m), 285 microM; V(rel), 5%) were also determined. Fructose acted as a C(3) donor at a high apparent K(m) (>/=M) and with a V(rel) of 12%. The enzyme was inhibited by Tris-HCl, phosphate, or sugars with the L configuration at C(2) (L-glyceraldehyde, D-arabinose-5-phosphate).

Amino Acid Sequence↗
PubMed1976

Oxidation of the carbanion intermediate of transaldolase by hexacyanoferrate (III).

The transaldolase-dihydroxyacetone carbanion intermediate formed in the reaction of transaldolase with its donor substrates fructose-6-P or sedoheptulose-7-P is susceptible to oxidation by hexacyanoferrate(III). The dihydroxyacetone moiety is oxidized to the corresponding 2-ketoaldehyde, i.e. hydroxy-pyruvaldehyde (CH2OH-CO-CHO). This oxidation product is, in contrast to dihydroxyacetone, readily released from the enzyme. In the presence of hexacyanoferrate(III) transaldolase thus functions as an efficient catalyst of the oxidative cleavage of its donor substrates fructose-6-P or sedoheptulose-7-P into hydroxypyruvaldehyde and glyceraldehyde-3-P or erythrose-4-P, respectively. Two moles of hexacyanoferrate(III) are reduced per mole of oxidatively cleaved donor substrate. The molecular activity for oxidative cleavage of fructose-6-P at a hexacyanoferrate(III) concentration of 0.5 mM is 0.65% of that for the normal transfer reaction with erythrose-4-P as the acceptor substrate. The present data emphasize the applicability of certain oxidants as trapping agents for enzymatic carbanion intermediates as proposed previously (Healy, M.J.,, and Christen, P. (1973) Biochemistry 12, 35-41).

Dihydroxyacetone↗
PubMed1997

Crystal structure of the reduced Schiff-base intermediate complex of transaldolase B from Escherichia coli: mechanistic implications for class I aldolases.

Transaldolase catalyzes transfer of a dihydroxyacetone moiety from a ketose donor to an aldose acceptor. During catalysis, a Schiff-base intermediate between dihydroxyacetone and the epsilon-amino group of a lysine residue at the active site of the enzyme is formed. This Schiff-base intermediate has been trapped by reduction with potassium borohydride, and the crystal structure of this complex has been determined at 2.2 A resolution. The overall structures of the complex and the native enzyme are very similar; formation of the intermediate induces no large conformational changes. The dihydroxyacetone moiety is covalently linked to the side chain of Lys 132 at the active site of the enzyme. The Cl hydroxyl group of the dihydroxyacetone moiety forms hydrogen bonds to the side chains of residues Asn 154 and Ser 176. The C3 hydroxyl group interacts with the side chain of Asp 17 and Asn 35. Based on the crystal structure of this complex a reaction mechanism for transaldolase is proposed.

Catalysis↗
PubMed1993

Lysine144 is essential for the catalytic activity of Saccharomyces cerevisiae transaldolase.

Replacement of lysine144 by glutamine in the pentose phosphate pathway enzyme transaldolase of Saccharomyces cerevisiae is associated with the complete loss of activity indicating the essential role in catalysis. Neither histidine nor cysteine is important for catalytic activity as proposed for the Candida utilis enzyme. Also we could not find any evidence for a half-site character of the enzyme as described for transaldolase of C. utilis. Therefore, the reaction mechanisms for the two enzymes are different.

Amino Acid Sequence↗
PubMed1979

Immunological relationships among transaldolases in the genus Bifidobacterium.

Antisera were prepared against electrophoretically homogeneous transaldolase (dihydroxyacetone transferase, E.C. 2.2.1.2.) of Bifidobacterium thermophilum (B. ruminale) RU326 (ATCC25866), B. cuniculi RA93 (ATCC27916) and B. 'minimum' (homology group) F392 (ATCC 27538). Crude extracts of eighty six strains previously assigned to twenty one species of the genus Bifidobacterium on the basis of deoxyribonouclelic acid (DNA) homology (DNA-DNA hybridization), were compared by double diffusion tests on Ouchterlony plates. Eight groups of identical antigenic specificity were recognized. By analysis of the spur formation, the groups of identical specificity were arranged in preliminary sequences of decreasing similarity to each of the three homologous transaldolases used as reference points. The relationships between immunological data and the genetic similarity among the species of the genus measured by means of DNA-DNA hybridization were discussed together with some relevant points of bifidal ecology.

Actinomycetaceae↗
PubMed1979

Preliminary quantification of immunological relationships among the transaldolases of the genus Bifidobacterium.

The immunological relatedness among the transaldolases (dihydroxyacetone transferase, E.C. 2.2.1.2) of twenty species of the genus Bifidobacterum has been tested by the microcomplement fixation method, using B. thermophilum (B. ruminale) RU326 (= ATCC 25866), B. cuniculi RA93 (= ATCC 27916) and B. 'minimum' (DNA homology group) F392 (= ATCC 27916) as references. Based on the serological relationships of the transaldolases, expressed either as indices of dissimilarity or as immunological distances, the twenty species of the genus Bifidobacterium were arranged into clusters. These clusters generally coincided with the immunological groups obtained previously by the immunodiffusion method (Sgorbati and Scardovi, 1979).

Actinomycetaceae↗
PubMed2004

Deletion of Ser-171 causes inactivation, proteasome-mediated degradation and complete deficiency of human transaldolase.

Homozygous deletion of three nucleotides coding for Ser-171 (S171) of TAL-H (human transaldolase) has been identified in a female patient with liver cirrhosis. Accumulation of sedoheptulose 7-phosphate raised the possibility of TAL (transaldolase) deficiency in this patient. In the present study, we show that the mutant TAL-H gene was effectively transcribed into mRNA, whereas no expression of the TALDeltaS171 protein or enzyme activity was detected in TALDeltaS171 fibroblasts or lymphoblasts. Unlike wild-type TAL-H-GST fusion protein (where GST stands for glutathione S-transferase), TALDeltaS171-GST was solubilized only in the presence of detergents, suggesting that deletion of Ser-171 caused conformational changes. Recombinant TALDeltaS171 had no enzymic activity. TALDeltaS171 was effectively translated in vitro using rabbit reticulocyte lysates, indicating that the absence of TAL-H protein in TALDeltaS171 fibroblasts and lymphoblasts may be attributed primarily to rapid degradation. Treatment with cell-permeable proteasome inhibitors led to the accumulation of TALDeltaS171 in whole cell lysates and cytosolic extracts of patient lymphoblasts, suggesting that deletion of Ser-171 led to rapid degradation by the proteasome. Although the TALDeltaS171 protein became readily detectable in proteasome inhibitor-treated cells, it displayed no appreciable enzymic activity. The results suggest that deletion of Ser-171 leads to inactivation and proteasome-mediated degradation of TAL-H. Since TAL-H is a regulator of apoptosis signal processing, complete deficiency of TAL-H may be relevant for the pathogenesis of liver cirrhosis.

Cells, Cultured↗
PubMed1993

Transaldolase mutants in the yeast Kluyveromyces lactis provide evidence that glucose can be metabolized through the pentose phosphate pathway.

We have isolated the gene encoding transaldolase from Kluyveromyces lactis (KITAL1) by screening a genomic library of this yeast using the TAL1 gene of Saccharomyces cerevisiae as a radioactive probe. The clone isolated contained an open reading frame of 1002 bp, encoding a protein with 76% identical residues in the deduced amino acid sequences as compared to Tal from S. cerevisiae. KITAL1 can complement a tal1 deletion of S. cerevisiae for enzymatic activity. The transcription start of KITAL1 was located at -69 bp relative to the ATG translation start codon. Deleting a large part of the open reading frame from the genome did not lead to any obvious phenotype. Transaldolase was not produced in such mutants as shown by immunological detection. In combination with a double null-mutant in the genes encoding the phosphofructokinase subunits in K. lactis (Klpfk1 Klpfk2 Kltal1), the cells lost their ability to grow on glucose. We take this as strong evidence that glucose is metabolized via the pentose phosphate pathway in this yeast when glycolysis is blocked. In addition, by tetrad analysis we detected a close linkage to KIPFK1 and inferred that KITAL1 is localized on chromosome I.

Amino Acid Sequence↗
PubMed1995

Xylose-metabolizing Saccharomyces cerevisiae strains overexpressing the TKL1 and TAL1 genes encoding the pentose phosphate pathway enzymes transketolase and transaldolase.

Saccharomyces cerevisiae was metabolically engineered for xylose utilization. The Pichia stipitis CBS 6054 genes XYL1 and XYL2 encoding xylose reductase and xylitol dehydrogenase were cloned into S. cerevisiae. The gene products catalyze the two initial steps in xylose utilization which S. cerevisiae lacks. In order to increase the flux through the pentose phosphate pathway, the S. cerevisiae TKL1 and TAL1 genes encoding transketolase and transaldolase were overexpressed. A XYL1- and XYL2-containing S. cerevisiae strain overexpressing TAL1 (S104-TAL) showed considerably enhanced growth on xylose compared with a strain containing only XYL1 and XYL2. Overexpression of only TKL1 did not influence growth. The results indicate that the transaldolase level in S. cerevisiae is insufficient for the efficient utilization of pentose phosphate pathway metabolites. Mixtures of xylose and glucose were simultaneously consumed with the recombinant strain S104-TAL. The rate of xylose consumption was higher in the presence of glucose. Xylose was used for growth and xylitol formation, but not for ethanol production. Decreased oxygenation resulted in impaired growth and increased xylitol formation. Fermentation with strain S103-TAL, having a xylose reductase/xylitol dehydrogenase ratio of 0.5:30 compared with 4.2:5.8 for S104-TAL, did not prevent xylitol formation.

Gene Expression Regulation, Enzymologic↗
PubMed2006

Study of transaldolase deficiency in urine samples by capillary LC-MS/MS.

Transaldolase (TAL) is a key enzyme of the pentose phosphate pathway (PPP). TAL deficiency is a newly recognized cause of liver cirrhosis. We have developed an ion-pair LC separation combined with negative ion electrospray MS/MS detection method to assess PPP metabolites in urine samples from TAL-deficient mice. Sedoheptulose 7-phosphate (S7P), C5-polyols D-arabitol and D-ribitol, and 6-phosphogluconate (6PG) levels were markedly increased in urine of TAL-deficient mice with respect to those of wild-type and heterozygote littermates. The detection limits of S7P, D-arabitol, and 6PG were 0.15 +/- 0.015 pmol, 3.5 +/- 0.41 pmol, and 0.61 +/- 0.055 pmol, respectively. The limit of quantitation was 0.4 +/- 0.024 nmol/ml for S7P, 1.6 +/- 0.11 nmol/ml for 6PG and 10 +/- 0.7 nmol/ml for D-arabitol. Additional metabolites, hexose 6-phosphates (m/z 259), D-ribose 5-phosphate and D-xylulose 5-phosphate (m/z 229), D-fructose 1,6-diphosphate (m/z 339), C6-polyols (m/z 181) and GSSG (m/z 611), that have been positively identified in mouse urine, showed similar levels in control and TAL-deficient mice.

Animals↗
PubMed1997

The human transaldolase gene (TALDO1) is located on chromosome 11 at p15.4-p15.5.

Transaldolase (TAL) is a key enzyme of the pentose phosphate pathway, which is responsible for generation of reducing equivalents to protect cellular integrity from reactive oxygen intermediates. While exons 2 and 3 are highly repetitive, the complete TAL-H gene is mapped to a single genomic locus (TALDO1(2)) by several independent approaches. Southern blot hybridization of a 827-bp 3' EcoRI fragment of the TAL-H cDNA to human-mouse somatic cell hybrid DNA localized TALDO1 to the p13-->pter region of chromosome 11. Fluorescence in situ hybridization with a 15-kb genomic fragment harboring exons 1 and 2 mapped TALDO1 to 11p15.4-p15.5. A truncated and mutated segment of TAL-H exon 5 terminating with a poly(A) tail was identified in a pseudogene locus (TALDOP1) on chromosome 1. Reverse transcriptase-PCR studies of human-mouse somatic cell hybrids revealed the presence of the functional TAL-H gene on chromosome 11 and its absence on human chromosome 1. Mapping of radiation hybrids placed TALDO1 between markers WI-1421 and D11S922 on 11p15.

Base Sequence↗