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PubMed2005

The dihydroxyacetone unit--a versatile C(3) building block in organic synthesis.

Nature employs dihydroxyacetone phosphate (DHAP) as the donor component in various enzyme-catalyzed aldol reactions. Probably the most significant example in this regard is photosynthesis, in which D-glucose, the most widespread natural product, is formed in just a few steps from DHAP. In recent years a number of synthetic equivalents of DHAP have been reported that deserve particular attention, as their applicability in organic synthesis is not limited to (stereoselective) aldol reactions. The power of these reagents has also been demonstrated convincingly in numerous other asymmetric electrophilic alpha-substitution reactions in target-oriented syntheses. Furthermore, the related 1,3-dioxins are useful equivalents of 2-substituted acrolein derivatives.

Acrolein↗
PubMed1976

Phosphorylation of glycerol and dihydroxyacetone in Acetobacter xylinum and its possible regulatory role.

Extracts of Acetobacter xylinum catalyze the phosphorylation of glycerol and dihydroxyacetone (DHA) by adenosine 5'-triphosphate (ATP) to form, respectively, L-alpha-glycerophosphate and DHA phosphate. The ability to promote phosphorylation of glycerol and DHA was higher in glycerol-grown cells than in glucose- or succinate-grown cells. The activity of glycerol kinase in extracts is compatible with the overall rate of glycerol oxidation in vivo. The glycerol-DHA kinase has been purified 210-fold from extracts, and its molecular weight was determined to be 50,000 by gel filtration. The glycerol kinase to DHA kinase activity ratio remained essentially constant at 1.6 at all stages of purification. The optimal pH for both reactions was 8.4 to 9.2. Reaction rates with the purified enzyme were hyperbolic functions of glycerol, DHA, and ATP. The Km for glycerol is 0.5 mM and that for DHA is 5 mM; both are independent of the ATP concentration. The Km for ATP in both kinase reactions is 0.5 mM and is independent of glycerol and DHA concentrations. Glycerol and DHA are competitive substrates with Ki values equal to their respective Km values as substrates. D-Glyceraldehyde and l-Glyceraldehyde were not phosphorylated and did not inhibit the enzyme. Among the nucleotide triphosphates tested, only ATP was active as the phosphoryl group donor. Fructose diphosphate (FDP) inhibited both kinase activities competitively with respect to ATP (Ki= 0.02 mM) and noncompetitively with respect to glycerol and DHA. Adenosine 5'-diphosphate (ADP) and adenosine 5'-monophosphate (AMP) inhibited both enzymic activities competitively with respect to ATP (Ki (ADP) = 0.4 mM; Ki (AMP) =0.25 mM). A. xylinum cells with a high FDP content did not grow on glycerol. Depletion of cellular FDP by starvation enabled rapid growth on glycerol. It is concluded that a single enzyme from A. xylinum is responsible for the phosphorylation of both glycerol and DHA. This as well as the sensitivity of the enzyme to inhibition by FDP and AMP suggest that it has a regulatory role in glycerol metabolism.

Adenosine Diphosphate↗
PubMed1999

Turbo-PUVA: dihydroxyacetone-enhanced photochemotherapy for psoriasis: a pilot study.

BACKGROUND: Dihydroxyacetone (DHA), a colorless sugar in "sunless" tanning lotions, binds to stratum corneum to form a UV-A-protective brown pigment. Bound DHA polymer is shed faster from hyperproliferative skin sites such as psoriatic plaques. We tested the hypothesis that selective shedding of DHA pigment during psoralen-UV-A (PUVA) treatment of psoriasis may allow higher UV-A doses, thus accelerating clearing while protecting uninvolved skin. Concurrent use of lactic acid was investigated as an aid in removing scale and residual DHA from psoriatic plaques. OBSERVATIONS: Thirty psoriatic patients with more than 20% body surface area involvement were recruited. The 6 PUVA study groups were (1) standard American style, (2) American style plus lactic acid, (3) DHA-PUVA or "topical ultraviolet-resisting barrier to optiimize PUVA" (Turbo-PUVA), (4) Turbo-PUVA with lactic acid, (5) European style, and (6) European style plus DHA. Combinations of lactic acid and European-style treatment were not studied. Each subject received up to 30 oral PUVA treatments twice weekly 3 days apart. The DHA-PUVA groups used 15% DHA lotion twice weekly. Lactic acid groups used 7% lotion daily except on treatment days. Psoriasis area and severity index scores were recorded weekly. Turbo-PUVA allowed higher UV-A exposures with minimal burns, showed faster clearing, and required fewer treatments for 90% clearing (P<.001). CONCLUSIONS: Protection of uninvolved skin by DHA during PUVA treatment allows higher UV-A exposures to be tolerated, demonstrates faster clearing, and requires fewer treatments to clear psoriasis. By reducing the total body dose received, Turbo-PUVA may also reduce long-term risks.

Adult↗
PubMed2002

Glyceraldehyde metabolism in human erythrocytes in comparison with that of glucose and dihydroxyacetone.

Metabolism of D-glyceraldehyde in human erythrocytes in comparison with that of glucose and dihydroxyacetone was studied. Both trioses were metabolized to produce L-lactate at rates comparable to that of L-lactate formation from glucose. Almost complete inactivation of glyceraldehyde-3-phosphate dehydrogenase by treatment of cells with iodoacetate resulted in a 95% decrease in L-lactate formation from the ketotriose as well as from glucose, whereas L-lactate formation from the aldotriose was only partially reduced (60%). D-Lactate was produced faster from either the aldotriose or the ketotriose than from glucose, but the ability of the two trioses to produce D-lactate was far lower than that to produce L-lactate. Almost complete inhibition of aldehyde dehydrogenase by disulfiram and of both aldose reductase and aldehyde reductase II by sorbinil, had no effect on L-lactate formation from D-glyceraldehyde. The present study suggests that D-glyceraldehyde is metabolized via two or more pathways including the glycolytic pathway after its phosphorylation by triokinase, and that neither oxidation to D-glyceric acid nor reduction to glycerol is a prerequisite for D-glyceraldehyde metabolism.

Carbohydrate Metabolism↗
PubMed2005

Aldol additions of dihydroxyacetone phosphate to N-Cbz-amino aldehydes catalyzed by L-fuculose-1-phosphate aldolase in emulsion systems: inversion of stereoselectivity as a function of the acceptor aldehyde.

The potential of L-fuculose-1-phosphate aldolase (FucA) as a catalyst for the asymmetric aldol addition of dihydroxyacetone phosphate (DHAP) to N-protected amino aldehydes has been investigated. First, the reaction was studied in both emulsion systems and conventional dimethylformamide (DMF)/H2O (1:4 v/v) mixtures. At 100 mM DHAP, compared with the reactions in the DMF/H2O (1:4) mixture, the use of emulsion systems led to two- to three-fold improvements in the conversions of the FucA-catalyzed reactions. The N-protected aminopolyols thus obtained were converted to iminocyclitols by reductive amination with Pd/C. This reaction was highly diastereoselective with the exception of the reaction of the aldol adduct formed from (S)-N-Cbz-alaninal, which gave a 55:45 mixture of both epimers. From the stereochemical analysis of the resulting iminocyclitols, it was concluded that the stereoselectivity of the FucA-catalyzed reaction depended upon the structure of the N-Cbz-amino aldehyde acceptor. Whereas the enzymatic aldol reaction with both enantiomers of N-Cbz-alaninal exclusively gave the expected 3R,4R configuration, the stereochemistry at the C-4 position of the major aldol adducts produced in the reactions with N-Cbz-glycinal and N-Cbz-3-aminopropanal was inverted to the 3R,4S configuration. The study of the FucA-catalyzed addition of DHAP to phenylacetaldehyde and benzyloxyacetaldehyde revealed that the 4R product was kinetically favored, but rapidly disappeared in favor of the 4S diastereoisomer. Computational models were generated for the situations before and after C-C bond formation in the active site of FucA. Moreover, the lowest-energy conformations of each pair of the resulting epimeric adducts were determined. The data show that the products with a 3R,4S configuration were thermodynamically more stable and, therefore, the major products formed, in agreement with the experimental results.

Aldehyde-Lyases↗
PubMed1997

Accumulation of sulfoquinovosyl-1-O-dihydroxyacetone in a sulfolipid-deficient mutant of Rhodobacter sphaeroides inactivated in sqdC.

The biosynthesis of the sulfolipid sulfoquinovosyl diacylglycerol in the purple bacterium Rhodobacter sphaeroides requires at least four genes:sqdA, sqdB, sqdC, and sqdD. As part of our strategy aimed at the elucidation of the function of the different sqd gene products, we insertionally inactivated sqdC of R. sphaeroides. The resulting sqdC null mutant showed only a 90% reduction in sulfolipid content. Apparently, the sqdC gene product is required for optimal sulfolipid biosynthesis, but either catalyzes no essential reaction in the pathway or can be functionally replaced to a certain extent by a different protein. The mutant accumulated a 35S-labeled compound that was purified to homogeneity from cell extracts. Matrix-assisted laser desorption mass spectrometry and nuclear magnetic resonance spectroscopy provided conclusive structural evidence to identify the compound as alpha-D-sulfoquinovosyl-1-O-dihydroxyacetone that exists in two interconvertible, keto and hemiacetal forms. Incubation of wild-type protein extracts with the labeled compound did not result in the incorporation into sulfolipid as would be expected for an intermediate of the pathway. Based on our results we propose that the sqdC gene product mediates the substrate specificity of the UDP-sulfoquinovose:diacylglycerol sulfoquinovosyltransferase that is encoded by sqdD and that catalyzes the final reaction of sulfolipid biosynthesis.

Bacterial Proteins↗
PubMed1996

Antidotal effect of dihydroxyacetone against cyanide toxicity in vivo.

Potassium cyanide (CN) intoxication in mice was found to be effectively antagonized by dihydroxyacetone (DHA), particularly if administered in combination with another CN antidote, sodium thiosulfate. Cyanide-induced convulsions were also prevented by DHA treatment, either alone or in combination with thiosulfate. Injection (i.p.) of DHA (2 g/kg) 2 min after or 10 min before CN (s.c.) increased LD50 values of CN(8.7 mg/kg) by factors of 2.1 and 3.0, respectively. Treatment with a combination of DHA and thiosulfate after CN increased the LD50 by a factor of 2.4. Pretreatment with a combination of DHA and thiosulfate (1 g/kg) increased the LD50 of CN to 83 mg/kg. Administration of alpha-ketoglutarate (2.0 g/kg), but not pyruvate, 2 min after CN increased the LD50 of CN by a factor of 1.6. Brain, heart and liver cytochrome oxidase activities were also measured following in vivo CN treatment with and without DHA. Pretreatment with DHA prevented the inhibition of cytochrome oxidase activity by CN and treatment with DHA after CN accelerated the recovery of cytochrome oxidase activity, especially in brain and heart homogenates. DHA is a physiological agent and, therefore, could prove to be a safe and effective antidote for CN, particularly in cases of fire smoke inhalation in which a combination of CN and carbon monoxide is present. In these cases the normally used antidote, sodium nitrite, to induce methemoglobin so as to trap the CN, is contraindicated because some of the oxygen-carrying capacity of the blood will have already been diminished by carbon monoxide.

Animals↗
PubMed1994

Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats.

In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle.

Adenosine Triphosphate↗
PubMed1978

Triglyceride synthesis from dihydroxyacetone phosphate and palmitate by microsomes from mammary glands of lactating mice.

Both di- and triglycerides were synthesized when microsomes isolated from mammary glands of lactating mice were incubated with dihydroxyacetone phosphate (DHAP), 1(-14)C)palmitate, ATP, CoASH, GSH, KF, MgC12, and NADPH. When NADH replaced NADPH, glyceride synthesis was very low. In the absence of either NADPH or NADH, DHAP was acylated to palmityl-DHAP. Since microsomes do not have glycerol 3-phosphate NAD:oxidoreductase activity , we inferred that glycerol 3-phosphate (GP) is not an intermediate in triglyceride biosynthesis from DHAP. This reductase, present in the cytosol, was active only with NADH. With the same concentration of either GP or DHAP, microsomes yielded essentially similar amounts of di- and triglycerides. Mitochondria, while capable of synthesizing palmityl-DHAP, did not produce di- and triglycerides.

Animals↗
PubMed2006

Small substrate, big surprise: fold, function and phylogeny of dihydroxyacetone kinases.

Dihydroxyacetone (Dha) kinases are a family of sequence-conserved enzymes which utilize either ATP (in animals, plants and eubacteria) or phosphoenolpyruvate (PEP, in eubacteria) as their source of high-energy phosphate. The kinases consist of two domains/subunits: DhaK, which binds Dha covalently in hemiaminal linkage to the Nepsilon2 of a histidine, and DhaL, an eight-helix barrel that contains the nucleotide-binding site. The PEP-dependent kinases comprise a third subunit, DhaM, which rephosphorylates in situ the firmly bound ADP cofactor. DhaM serves as the shuttle for the transfer of phosphate from the bacterial PEP: carbohydrate phosphotransferase system (PTS) to the Dha kinase. The DhaL and DhaK subunits of the PEP-dependent Escherichia coli kinase act as coactivator and corepressor of DhaR, a transcription factor from the AAA(+) family of enhancerbinding proteins. In Gram-positive bacteria genes for homologs of DhaK and DhaL occur in operons for putative transcription factors of the TetR and DeoR families. Proteins with the Dha kinase fold can be classified into three families according to phylogeny and function: Dha kinases, DhaK and DhaL homologs (paralogs) associated with putative transcription regulators of the TetR and DeoR families, and proteins with a circularly permuted domain order that belong to the DegV family.

Citrobacter freundii↗
PubMed2006

A metabolic study of the regulation of proteolysis by sugars in maize root tips: effects of glycerol and dihydroxyacetone.

Sugars, the main growth substrates of plants, act as physiological signals in the complex regulatory network of sugar metabolism. To investigate the function of different glycolytic steps in sugar sensing and signaling we compared the effects of carbon starvation with those of glucose, glycerol and dihydroxyacetone on carbon metabolism, proteolysis, and protease expression in excised maize (Zea mays L.) root tips. Respiration, soluble proteins, protein turnover and proteolytic activities were monitored as a function of time, along with in vitro and in vivo analysis of a variety of metabolites (sugars, amino and organic acids, phosphoesters, adenine nucleotides...) using (13)C, (31)P and (1)H NMR spectroscopy. Our results indicate that, in maize root tips, endopeptidase activities and protease expression are induced in response to a decrease in carbon supply to the upper part of the glycolytic pathway, i.e. at the hexokinase step. Proteolysis would be controlled downstream glycolysis, probably at the level of the respiratory substrate supply to mitochondria.

Carbohydrates↗
PubMed2003

Optimization of the microbial synthesis of dihydroxyacetone from glycerol with Gluconobacter oxydans.

An optimized repeated-fed-batch fermentation process for the synthesis of dihydroxyacetone (DHA) from glycerol utilizing Gluconobacter oxydans is presented. Cleaning, sterilization, and inoculation procedures could be reduced significantly compared to the conventional fed-batch process. A stringent requirement was that the product concentration was kept below a critical threshold level at all times in order to avoid irreversible product inhibition of the cells. On the basis of experimentally validated model calculations, a threshold value of about 60 kg x m(-3) DHA was obtained. The innovative bioreactor system consisted of a stirred tank reactor combined with a packed trickle-bed column. In the packed column, active cells could be retained by in situ immobilization on a hydrophilized Ralu-ring carrier material. Within 17 days, the productivity of the process could be increased by 75% to about 2.8 kg x m(-3) h(-1). However, it was observed that the maximum achievable productivity had not been reached yet.

Bioreactors↗
PubMed2005

Study of the inhibitory effect of the product dihydroxyacetone on Gluconobacter oxydans in a semi-continuous two-stage repeated-fed-batch process.

The influence of the product inhibition by dihydroxyacetone (DHA) on Gluconobacter oxydans for a novel semi-continuous two-stage repeated-fed-batch process was examined quantitatively. It was shown that the culture was able to grow up to a DHA concentration of 80 kg m(-3) without any influence of product inhibition. The regeneration capability of the reversibly product inhibited culture from a laboratory-scale bioreactor system was observed up to a DHA concentration of about 160 kg m(-3). At higher DHA concentrations, the culture was irreversibly product inhibited. However, due to the robust membrane-bound glycerol dehydrogenase of G. oxydans, product formation was still active for a prolonged period of time. The reachable maximum final DHA concentration was as high as 220 kg m(-3). The lag phases for growth increased exponentially with increasing DHA threshold values of the first reactor stage. These results correlated well with fluorescence in situ hybridization (FISH) measurements confirming that the number of active cells decreased exponentially with increasing DHA concentrations.

Bioreactors↗
PubMed1987

Superoxide radical initiates the autoxidation of dihydroxyacetone.

The aerobic xanthine oxidase reaction causes the cooxidation of dihydroxyacetone in a process which is strongly inhibited by superoxide dismutase but not by catalase, HO X scavengers, or iron-inactivating chelating agents. Several molecules of the sugar can be oxidized per O2- introduced. A free radical chain mechanism, in which O2- acts both as an initiator and as a chain propagator, is proposed. Simple sugars capable of tautomerizing to enediols may now be added to the list of biologically relevant targets for O2-.

Catalase↗
PubMed1986

Mechanism for the oleate stimulation of gluconeogenesis from dihydroxyacetone by hepatocytes from fasted rats.

Oleate stimulates glucose production and concomitantly decreases lactate and pyruvate production by rat hepatocyte suspensions incubated with dihydroxyacetone as substrate. The actions of oleate could be blocked by D-(+)dodecanoylcarnitine, which inhibits transport of the fatty acid into the mitochondria and the subsequent oxidation. beta-Hydroxybutyrate, but not acetoacetate, also stimulated glucose synthesis and inhibited lactate and pyruvate production. Furthermore, both beta-hydroxybutyrate and oleate stimulated oxygen consumption to the same extent. This suggests that oleate stimulates glucose production by the provision of energy subsequent to mitochondrial beta-oxidation of the fatty acids. The content of ATP itself did not appear to be responsible for the effects of oleate. Crossover analysis of the gluconeogenic intermediates implicated a site of oleate action between fructose 1,6-bisphosphate and fructose 6-phosphate, suggesting phosphofructokinase and/or fructose-bisphosphatase as possible regulatory sites. Coupled with the finding that intracellular citrate accumulates upon addition of oleate or beta-hydroxybutyrate, but not acetoacetate, the results suggest that citrate inhibition of phosphofructokinase accounts for the redirection of carbon flow from lactate and pyruvate formation and towards that of glucose.

Animals↗
PubMed1977

The mode of condensation of aspartic acid and dihydroxyacetone phosphate in quinolinate synthesis in Escherichia coli.

Dihydroxy [3-14C]acetone phosphate was prepared enzymatically from [1-14C]glucose and use as a substrate in a partially purified quinolinate synthetase system prepared from Escherichia coli mutants. Carbon-by-carbon degradation of the resulting [14C]quinolinate showed that 96% of the 14C was located in carbon-4, indicating that carbon-3 of dihydroxyacetone phosphate condenses with carbon-3 of aspartate in quinolinate synthesis in E. coli.

Aspartic Acid↗