SEARCH · PubMed Health

Results for “Transaldolase”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1990

Molecular analysis of the structural gene for yeast transaldolase.

We have cloned the structural gene for yeast transaldolase. Transformants carrying the TAL1 gene on a multicopy plasmid over-produced transaldolase. A deletion mutant which was constructed using the cloned gene did not show any detectable transaldolase activity in vitro. Furthermore, both transaldolase isoenzymes which were detected in wild-type crude extracts by immunoblotting were missing in the deletion mutants. Thus, TAL1 is the only transaldolase structural gene in yeast. TAL1 is not an essential gene. Deletion of the transaldolase gene did not affect growth on complete media with different carbon sources or on synthetic media. However, the transaldolase-deficient strains accumulated sedoheptulose 7-phosphate, an intermediate of the pentose-phosphate pathway. Mutants lacking both transaldolase and phosphoglucose isomerase grew more slowly than the single mutants. They accumulated more sedoheptulose 7-phosphate on medium containing fructose than on glucose medium. This shows that fructose 6-phosphate and glyceraldehyde 3-phosphate, metabolites of glycolysis, can enter the nonoxidative part of the pentose-phosphate pathway.

Amino Acid Sequence↗

PubMed1976

Behavior of transaldolase (EC 2.2.1.2) and transketolase (EC 2.2.1.1) Activities in normal, neoplastic, differentiating, and regenerating liver.

The objective of this investigation was to throw light on the biological behavior and metabolic regulation of hepatic enzymes of the nonoxidative branch of the pentose phosphate pathway. The activities of transaldolase (EC 2.2.1.2) and trasketolase (EC 2.2.1.1) Were compared in biological conditions that involve modulation of gene expression such as in starvation, in differentiation, after partial hepatectomy, and in a spectrum of hepatomas of different growth rates. The enzyme activities were determined under optimal kinetic conditions by spectrophotometric methods in the 100,000 X g supernatant fluids prepared from tissue homogenates. The kinetic properties of transaldolase and transketolase were similar in normal liver and in rapidly growing hepatoma 3924A. For transaldolase, apparent Km values of 0.13 mM (normal liver) and 0.17 mM (hepatoma) were observed for erythrose 4-phosphate and of 0.30 to 0.35 mM for fructose 6-phosphate. The pH optima in liver and hepatoma were at approximately 6.9 to 7.2. For the transketolase substrates, ribose 5-phosphate and xylulose 5-phosphate, the apparent Km values were 0.3 and 0.5 mM, respectively, in both liver and hepatoma. A broad pH optimum around 7.6 was observed in both tissues. In organ distribution studies, enzyme activities were measured in liver, intestinal mucosa, thymus, kidney, spleen, brain, adipose tissue, lung, heart, and skeletal muscle. Taking the specific activity of liver as 100%, transaldolase activity was the highest in intestinal mucosa (316%) and in thymus (219%); it was the lowest in heart (53%) and in skeletal muscle (21%). Transketolase activity was highest in kidney (155%) and lowest in heart (26%) and skeletal muscle (23%). Starvation decreased transaldolase and transketolase activities in 6 days to 69 and 74%, respectively, of those of the liver of the normal, fed rat. This was in the same range as the decrease in the protein concentration (66%y. In the liver tumors, transaldolase activity was increased 1.5- to 3.4-fold over the activities observed in normal control rat liver. Transketolase activity showed no relationship to tumor proliferation rate. In the regenerating liver at 24 hr after partial hepatectomy, the activity of both pentose phosphate pathway enzymes was in the same range as that of the sham-operated controls. In differentiation at the postnatal age of 5, 12, 23, and 32 days, hepatic transaldolase activities were 33, 44, 55, and 72%, respectively, of the activities observed in the 60-day-old, adult male rat. During the same period, transketolase activ-ties were 18, 21, 26, and 55% of the activities observed in liver of adult rat. The demonstration of increased transaldolase activity in hepatomas, irrespective of the degree of tumor malignancy, differentiation, or growth rate, suggests that the reprogramming of gene expression in malignant transformation is linked with an increase in the expression of this pentose phosphate pathway enzyme...

Animals↗

PubMed1991

Effects of increased transaldolase activity on D-xylulose and D-glucose metabolism in Saccharomyces cerevisiae cell extracts.

In vitro metabolism of D-xylulose and D-glucose in extracts obtained from D-glucose- and D-xylulose-fermenting Saccharomyces cerevisiae cells was investigated with 10- and 100-fold-increased activity of the enzyme transaldolase (EC 2.2.1.2). The rate of sugar consumption was the same in most cases, whereas the rate of ethanol formation decreased with increased levels of transaldolase. The formation of glycerol, pentitols, and acetic acid was not dependent on added transaldolase but was dependent on the sugar used as the growth substrate and on the sugar used in the in vitro metabolism experiments. The carbon balance showed that the dissimilated carbon could not be accounted for in products when transaldolase was added. The concentration of D-fructose-1,6.-diphosphate in the extracts was not influenced by added transaldolase but was higher with D-xylulose than with D-glucose. Levels of pyruvate, comparable with the two substrates, decreased with increasing levels of transaldolase. Exogenously added transaldolase decreased D-sedoheptulose-7-phosphate levels when D-xylulose was the substrate. The results are discussed in relation to the dissimilation of carbon through the upper part of glycolysis and the pentose phosphate pathway.

Biological Transport↗

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↗

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↗

PubMed1974