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PubMed2003

Dihydroxyacetone-induced oscillations in cytoplasmic free Ca2+ and the ATP/ADP ratio in pancreatic beta-cells at substimulatory glucose.

Glucose stimulation of pancreatic beta-cells causes oscillatory influx of Ca2+, leading to pulsatile insulin secretion. We have proposed that this is due to oscillations of glycolysis and the ATP/ADP ratio, which modulate the activity of ATP-sensitive K+ channels. We show here that dihydroxyacetone, a secretagogue that feeds into glycolysis below the putative oscillator phosphofructokinase, could cause a single initial peak in cytoplasmic free Ca2+ ([Ca2+]i) but did not by itself cause repeated oscillations in [Ca2+]i in mouse pancreatic beta-cells. However, in the presence of a substimulatory concentration of glucose (4 mm), dihydroxyacetone induced [Ca2+]i oscillations. Furthermore, these oscillations correlated with oscillations in the ATP/ADP ratio, as seen previously with glucose stimulation. Insulin secretion in response to dihydroxyacetone was transient in the absence of glucose but was considerably enhanced and somewhat prolonged in the presence of a substimulatory concentration of glucose, in accordance with the enhanced [Ca2+]i response. These results are consistent with the hypothesized role of phosphofructokinase as the generator of the oscillations. Dihydroxyacetone may affect phosphofructokinase by raising the free concentration of fructose 1,6-bisphosphate to a critical level at which it activates the enzyme autocatalytically, thereby inducing the pulses of phosphofructokinase activity that cause the metabolic oscillations.

Adenosine Diphosphate↗
PubMed2004

Modulated photoacoustic spectroscopy study of an artificial tanning on human skin induced by dihydroxyacetone.

A modulated photoacoustic spectroscopy study on the effect of dihydroxyacetone, commonly used for artificial tan, is presented. The study was carried out in the presence and absence of dimethylisosorbide (a solvent for dihydroxyacetone) on fresh human skin, obtained from the breast region of recent autopsy cases (two females), at a frequency of 25 Hz, which enabled us to study the effect at a depth of 30 microm in the stratum corneum and beneath. By monitoring the photoacoustic signal intensity with time in the region of 300-400 nm, which is a specific region for melanin pigment, it is demonstrated that dihydroxyacetone in combination with dimethylisosorbide enhances the process of tanning. Dihydroxyacetone also has an effect on the amino acids and nucleic acids which is bad for the skin.

Acoustics↗
PubMed1976

Hormonal control of [14C]glucose synthesis from [U-14C]dihydroxyacetone and glycerol in isolated rat hepatocytes.

The hormonal control of [14C]glucose synthesis from [U-14C-A1dihydroxyacetone was studied in hepatocytes from fed and starved rats. In cells from fed rats, glucagon lowered the concentration of substrate giving half-half-maximal rates of incorporation while it had little or no effect on the maximal rate. Inhibitors of gluconeogenesis from pyruvate had no effect on the ability of the hormone to stimulate the synthesis of [14C]glucose from dihydroxyacetone. The concentrations of glucagon and epinephrine giving half-maximal stimulation from dihydroxacetone were 0.3 to 0.4 mM and 0.3 to 0.5 muM, respectively. The meaximal catecholamine stimulation was much less than the maximal stimulation by glucagon and was mediated largely by the alpha receptor. Insulin had no effect on the basal rate of [14C]clucose synthesis but inhibited the effect of submaximal concentration of glucagon or of any concentration of catecholamine. Glucagon had no effect on the uptake of dihydroxyacetone but suppressed its conversion to lactate and pyruvate. This suppression accounted for most of the increase in glucose synthesis. In cells from gasted rats, where lactate production is greatly reduced and the rate of glucose synthesis is elevated, glucagon did not stimulate gluconeogenesis from dihydroxyacetone. Findings with glycerol as substrate were similar to those with dihyroxyacetone. Ethanol also stimulated glucose production from dihydroxyacetone while reducing proportionately the production of lactate. Ethanol is known to generate reducing equivalents fro clyceraldehyde-3-phosphate dehydrogenase and presumably thereby inhibits carbon flux to lactate at this site. Its effect was additive with that of glucagon. Estimates of the steady state levels of intermediary metabolites and flux rates suggested that glucagon activated conversion of fructose diphosphate to fructose 6-phosphate and suppressed conversion of phosphoenolpyruvate to pyruvate. More direct evidence for an inhibition of pyruvate kinase was the observation that brief exposure of cells to glucagon caused up to 70% inhibition of the enzyme activity in homogenates of these cells. The inhibition was not seen when the enzyme was assayed with 20 muM fructose diphosphate. The effect of glucagon to lower fructose diphosphate levels in intact cells may promote the inhibition of pyruvate kinase. The inhibition of pyruvate kinase may reduce recycling in the pathway of gluconeogenesis from major physiological substrates and probably accounts fromsome but not all the stimulatory effect of glucagon.

Animals↗
PubMed1986

Acyl-CoA:dihydroxyacetone phosphate acyltransferase in human skin fibroblasts: study of its properties using a new assay method.

In relation to the finding that human skin fibroblasts are capable of de novo either phospholipid biosynthesis, we have studied the properties of acyl-CoA:dihydroxyacetone phosphate acyltransferase in fibroblast homogenates using a new assay method. The results indicate that the acylation of dihydroxyacetone phosphate shows an optimum at pH 5.5 with a broad shoulder of activity up to pH 6.4 and a decline in activity up to pH 8.2. At pH 5.5 the acyltransferase accepts dihydroxyacetone phosphate, but not glycerol 3-phosphate as a substrate. Furthermore, the transferase activity was found to be membrane-bound and inactivated by Triton X-100 at concentrations above 0.025% (w/v). Similar properties have been described for the enzyme as present in rat-liver and guinea-pig liver peroxisomes. These data, together with the finding that acyl-CoA:dihydroxyacetone phosphate acyltransferase is deficient in cultured skin fibroblasts from patients without peroxisomes (Zellweger syndrome), suggest that in cultured skin fibroblasts the enzyme is primarily located in peroxisomes.

Acyltransferases↗
PubMed1999

Molecular characterisation of Trypanosoma brucei alkyl dihydroxyacetone-phosphate synthase.

Alkyl dihydroxyacetone-phosphate synthase is the second enzyme of the ether-lipid biosynthetic pathway which is responsible for the introduction of the ether linkage between a fatty alcohol and a glycerol present in a subclass of phospholipids, the plasmalogens and possibly in glycolipid membrane anchors. In this study the gene coding for alkyl dihydroxyacetone-phosphate synthase was isolated from Trypanosoma brucei. Southern blot analysis of total genomic DNA suggested the presence of a single copy gene. The analysis, together with sequencing of different cDNA clones showed that the two alleles of the gene differ in only one nucleotide. The gene encodes a protein of 612 amino acids with a calculated molecular mass of 68,891, not counting the initiator methionine. It carries a type-1 peroxisomal targeting signal (a C-terminal tripeptide--AHL) and a calculated overall positive charge of +10. The gene was expressed in a bacterial system and the corresponding protein carrying a His-tag was purified. The recombinant alkyl dihydroxyacetone-phosphate synthase and the enzyme isolated directly from the glycosomes of bloodstream-form trypanosomes have comparable kinetics. The Km for hexadecanol was 42 microM, while approximately 100 microM of palmitoyl dihydroxyacetone phosphate (DHAP) was necessary for optimal activity. Sodium chloride inhibited both the His-tagged protein and the enzyme isolated from the glycosomes of bloodstream-form and insect stage T. brucei.

Alkyl and Aryl Transferases↗
PubMed1971

Dihydroxyacetone phosphate. Its structure and reactivity with -glycerophosphate dehydrogenase, aldolase and triose phosphate isomerase and some possible metabolic implications.

1. Dihydroxyacetone phosphate exists in neutral aqueous solution at 20 degrees C as a mixture of keto, gem-diol and enolic forms in the ratio 55:44:1. 2. The three forms are freely interconvertible and rate constants for these reactions have been determined. 3. Keto-dihydroxyacetone phosphate is the primary reactive species in the reactions catalysed by alpha-glycerophosphate dehydrogenase, aldolase and triose phosphate isomerase. 4. The proportion of keto form to gem-diol forms of dihydroxyacetone phosphate is temperature-dependent. At 37 degrees C, 83% is keto-dihydroxyacetone phosphate. 5. The enzymological and metabolic consequences of these results are discussed.

Acetone↗
PubMed1973

The tritium isotope effect of sn-glycerol 3-phosphate oxidase and the effects of clofenapate and N-(2-benzoyloxyethyl)norfenfluramine on the esterification of glycerol phosphate and dihydroxyacetone phosphate by rat liver mitochondria.

1. Owing to a (3)H isotope effect, the mitochondrial sn-glycerol 3-phosphate oxidase (EC 1.1.99.5) had a mean activity which was 8.4 times less with sn-[2-(3)H]-rather than with sn-[1-(14)C]glycerol 3-phosphate as a substrate. 2. A method for measuring the simultaneous synthesis of lipid from glycerol phosphate and dihydroxyacetone phosphate in rat liver mitochondria is described. 3. The lipid synthesized by rat liver mitochondria from sn-[1-(14)C]glycerol 3-phosphate was mainly phosphatidate and lysophosphatidate, whereas that synthesized from dihydroxy[1-(14)C]acetone phosphate was mainly acyldihydroxyacetone phosphate. 4. Additions of NADPH facilitated the conversion of acyldihydroxyacetone phosphate into lysophosphatidate and phosphatidate. 5. Hydrazine (1.4mm) or KCN (1.4mm) inhibited the synthesis of lipids from dihydroxyacetone phosphate but not from glycerol phosphate. 6. Clofenapate (1-2.5mm) inhibited the synthesis of lipids from dihydroxyacetone phosphate but slightly stimulated synthesis from glycerol phosphate. 7. The methanesulphonate of N-(2-benzoyloxyethyl)norfenfluramine, at 0.25-0.75mm, inhibited lipid synthesis from both glycerol phosphate and dihydroxyacetone phosphate.

Acetone↗
PubMed2005

From ATP as substrate to ADP as coenzyme: functional evolution of the nucleotide binding subunit of dihydroxyacetone kinases.

Dihydroxyacetone kinases are a family of sequence-related enzymes that utilize either ATP or a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) as a source of high energy phosphate. The PTS is a multicomponent system involved in carbohydrate uptake and control of carbon metabolism in bacteria. Phylogenetic analysis suggests that the PTS-dependent dihydroxyacetone kinases evolved from an ATP-dependent ancestor. Their nucleotide binding subunit, an eight-helix barrel of regular up-down topology, retains ADP as phosphorylation site for the double displacement of phosphate from a phospho-histidine of the PTS protein to dihydroxyacetone. ADP is bound essentially irreversibly with a t((1/2)) of 100 min. Complexation with ADP increases the thermal unfolding temperature of dihydroxyacetone L from 40 (apo-form) to 65 degrees C (holoenzyme). ADP assumes the same role as histidines, cysteines, and aspartic acids in histidine kinases and PTS proteins. This conversion of a substrate binding site into a cofactor binding site reflects a remarkable instance of parsimonious evolution.

Adenosine Diphosphate↗
PubMed2006

Leishmania major expresses a single dihydroxyacetone phosphate acyltransferase localized in the glycosome, important for rapid growth and survival at high cell density and essential for virulence.

Despite major advances in the understanding of pathogenesis of the human protozoan parasite Leishmania major, little is known about the enzymes and the primary precursors involved in the initial steps of synthesis of its major glycerolipids including those involved in virulence. We have previously demonstrated that the initial step of acylation of the precursor glycerol 3-phosphate is not essential for the synthesis of ester and ether phospholipids in this parasite. Here we show that Leishmania expresses a single acyltransferase with high specificity for the precursor dihydroxyacetone phosphate and shows the best activity in the presence of palmitoyl-CoA. We have identified and characterized the LmDAT gene encoding this activity. LmDAT complements the lethality resulting from the loss of both dihydroxyacetone phosphate and glycerol-3-phosphate acyltransferase activities in yeast. Recombinant LmDAT exhibits biochemical properties similar to those of the native enzyme of the promastigote stage parasites. We show that LmDAT is a glycosomal enzyme and its loss in a delta lmdat/delta lmdat null mutant results in complete abrogation of the parasite dihydroxyacetone phosphate acyltransferase activity. Furthermore, lack of LmDAT causes a major alteration in parasite division during the logarithmic phase of growth, an accelerated cell death during stationary phase, and loss of virulence. Together, our results demonstrate that LmDAT is the only dihydroxyacetone phosphate acyltransferase of the L. major localized in the peroxisome, important for growth and survival and essential for virulence.

Acyltransferases↗
PubMed1983

Evidence for Endogenous Cyclic Photophosphorylation in Intact Chloroplasts: CO(2) Fixation with Dihydroxyacetone Phosphate.

This study examines the capacity of intact spinach (Spinacia oleracea L.) chloroplasts to fix (14)CO(2) when supplied with Benson-Calvin cycle intermediates in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Under these conditions, substantial (14)CO(2) fixation occurred in the light but not in the dark when either dihydroxyacetone phosphate, ribulose 5-phosphate, fructose 6-phosphate, or fructose bisphosphate was added. The highest rate of (14)CO(2) fixation (20-40 micromoles per milligram chlorophyll per hour) was obtained with dihydroxyacetone phosphate. In contrast, no (14)CO(2) fixation occurred when 3-phosphoglycerate was used. (14)CO(2) fixation in the presence of dihydroxyacetone phosphate and DCMU was inhibited by carbonylcyanide m-chlorophenylhydrazone, dl-glyceraldehyde, and pyridoxal 5'-phosphate. Low concentrations of O(2) (25-50 micromolar) stimulated (14)CO(2) fixation, but the activity decreased with increasing O(2) concentrations. The fixation of (14)CO(2) in the presence of DCMU and dihydroxyacetone phosphate was also observed in maize bundle sheath cells. These results provide direct evidence for cyclic photophosphorylation in intact chloroplasts. The activity measured is adequate to support all the extra ATP requirements for maximum rates of photosynthesis in these intact chloroplasts.

Journal Article↗
PubMed1985

Dihydroxyacetone synthase is an abundant constituent of the methanol-induced peroxisome of Candida boidinii.

Methylotrophic yeasts induce large peroxisomes when grown on methanol. The recent ability to stabilize and isolate these peroxisomes at pH 5.5 has led to the demonstration that two polypeptides comprise the bulk of the peroxisome of Candida boidinii, alcohol oxidase, and a 79-kDa species, determined by sodium dodecyl sulfate-polyacrylamide electrophoresis (Goodman, J.M., Scott, C.W., Donahue, P.N., and Atherton, J.P. (1984) J. Biol. Chem. 259, 8485-8493). The 79-kDa peroxisomal protein is now identified as dihydroxyacetone synthase, the first enzyme in the assimilatory pathway of formaldehyde utilization. This identification is based on several criteria: The enzyme activity is mainly in a particulate fraction at pH 5.5 but not at pH 8.0. It copurifies with alcohol oxidase and catalase on sucrose gradients. The 79-kDa protein behaves as a 135,000-kDa dimer on gel filtration, similar to the published behavior of the enzyme. The specific activity of dihydroxyacetone synthase in the pure 79-kDa preparation (3.20 units/mg of protein) is close to that reported for the purified enzyme (3.88 units/mg of protein). Antibodies against dihydroxyacetone synthase were used to show that its synthesis, induction, and assembly are similar to that of alcohol oxidase. Neither contains a detectable cleaved leader sequence and both are assembled post-translationally. The localization of dihydroxyacetone synthase to the peroxisome may influence the regulation of the two pathways of formaldehyde utilization and may protect the cell from damage by formaldehyde.

Aldehyde-Ketone Transferases↗
PubMed1981

[Dihydroxyacetone synthase from the methanol-utilizing yeast Candida boidinii].

A procedure for purification of dihydroxyacetone synthase catalyzing the formation of dihydroxyacetone and glyceraldehyde 3-phosphate from formaldehyde and xylulose 5-phosphate has been developed. Using ion-exchangers with increasing affinity for dihydroxyacetone synthase, a homogenous preparation of the enzyme with specific activity of 2 u./mg has been obtained. The enzyme is made up of 2 subunits with m. w. of 76,000, contains thiamine pyrophosphate, requires Mg2+ for its activity and differs from yeast transketolase by substrate specificity and some other properties. The role of dihydroxyacetone synthase in metabolism of methanol-utilizing yeasts is discussed.

Aldehyde-Ketone Transferases↗
PubMed1998

The Pichia pastoris dihydroxyacetone kinase is a PTS1-containing, but cytosolic, protein that is essential for growth on methanol.

Dihydroxyacetone kinase (DAK) is essential for methanol assimilation in methylotrophic yeasts. We have cloned the DAK gene from Pichia pastoris by functional complementation of a mutant that was unable to grow on methanol. An open reading frame of 1824 bp was identified that encodes a 65.3 kDa protein with high homology to DAK from Saccharomyces cerevisiae. Although DAK from P. pastoris contained a C-terminal tripeptide, TKL, which we showed can act as a peroxisomal targeting signal when fused to the green fluorescent protein, the enzyme was primarily cytosolic. The TKL tripeptide was not required for the biochemical function of DAK because a deletion construct lacking the DNA encoding this tripeptide was able to complement the P. pastoris dak delta mutant. Peroxisomes, which are essential for growth of P. pastoris on methanol, were present in the dak delta mutant and the import of peroxisomal proteins was not disturbed. The dak delta mutant grew at normal rates on glycerol and oleate media. However, unlike the wild-type cells, the dak delta mutant was unable to grow on methanol as the sole carbon source but was able to grow on dihydroxyacetone at a much slower rate. The metabolic pathway explaining the reduced growth rate of the dak delta mutant on dihydroxyacetone is discussed. The nucleotide sequence reported in this paper has been submitted to GenBank with Accession Number AF019198.

Amino Acid Sequence↗
PubMed1981

Characterisation of the abnormal pancreatic D and A cell function in streptozotocin diabetic dogs: studies with D-glyceraldehyde, dihydroxyacetone, D-mannoheptulose, D-glucose, and L-arginine.

Pancreatic D and A cell function is deranged in streptozotocin diabetes. To investigate this, the effect of D-glyceraldehyde, dihydroxyacetone, D-mannoheptulose and glucose variations during arginine stimulation on the release of somatostatin and glucagon from the isolated pancreas of normal and streptozotocin diabetic dogs was studied. Concentrations of the trioses, D-glyceraldehyde (1.25 and 2.5 mmol/l) and dihydroxyacetone (11 mmol/l), which normally stimulate D cells, did not influence the release of somatostatin in the diabetic dog. However, the higher concentration of D-glyceraldehyde (5 mmol/l) and dihydroxyacetone (11 mmol/l), which normally stimulate D cells, did not influence the release of somatostatin in the diabetic dog. However, the higher concentration of D-glyceraldehyde (5 mmol/l) suppressed D cell ssecretion in the diabetic animals at 0 and 8.3 mmol/l glucose. A cell secretion was significantly suppressed at the higher glucose level in response to both 2.5 and 5 mmol/l of te triose. This inhibition may be explained by a non-specific effect induced by the high dose of this triose. The addition of 5 mmol/l mannoheptulose, which normally reduces glucose-induced somatostatin secretion and stimulates glucagon release, did not affect hormone secretion. In both the diabetic and the normal animals, arginine (5 mmol/l) stimulated somatostatin and glucagon secretion. Although arginine was able to stimulate D and A cell secretion in the diabetic dogs, it was however unable to restore the response to changes in glucose concentration between 1.4 and 8.3 mmol/l to normal. These results demonstrate that the abnormal pancreatic D and A cell function in streptozotocin diabetes is characterised by an impaired response to glucose and certain glucose metabolites and probably results from a specific defect in glucose recognition.

Animals↗
PubMed2002

Microencapsulation of Aerococcus viridans with catalase and its application for the synthesis of dihydroxyacetone phosphate.

Dihydroxyacetone phosphate is essential for the synthesis of polyhydroxylated compounds used as components or precursors of active pharmaceutical substances, such as antibiotics or glycosidase inhibitors. Dihydroxyacetone phosphate was produced by enzymatic oxidation of L-alpha-glycerophosphate in the presence of glycerophosphate oxidase or Aerococcus viridans coimmobilized with a hydrogen peroxide-decomposing enzyme. The microencapsulation of A. viridans with catalase in sodium alginate showed a conversion of 98.5%; the conversion percentage remained constant in all five runs. Liquid chromatography of the product revealed that the product peak corresponded to that of the dihydroxyacetone phosphate internal standard. This indicated a high degree of product purity.

Alginates↗
PubMed1989

Effect of glycerol and dihydroxyacetone on hepatic lipogenesis.

Glycerol is a dietary component which is metabolized primarily by the liver and kidney where it is used mainly for glucose synthesis. The metabolism of glycerol is very similar to that of dihydroxyacetone which can be considered its more oxidized counterpart. The effects of these substrates on hepatic lipogenesis and gluconeogenesis were examined. In isolated hepatocytes, 10 mM dihydroxyacetone caused a large increase in glucose output and stimulated lipogenesis without affecting the lactate/pyruvate ratio or the total ATP content of the cells. (As compared to dihydroxyacetone, 10 mM glycerol was less effective as a gluconeogenic substrate, increased the lactate/pyruvate ratio, caused a slight decrease in the total ATP content, and inhibited lipogenesis by at least 40% depending on the type of diet fed to the rats.) The fall in ATP levels was very small and did not correlate with the changes in fatty acid synthesis. The immediate cause of the inhibition of lipogenesis, brought about by glycerol in hepatocytes from sucrose fed rats, seemed to be a large decrease in pyruvate levels. This did not result from impairment of glycolysis but from a rise in the cytosolic NADH/NAD ratio.

3-Hydroxybutyric Acid↗
PubMed1977

The effect of dihydroxyacetone phosphate and 3-phosphoglycerate on O2 evolution and on the levels of ATP, ADP and Pi in isolated intact chloroplasts.

Addition of dihydroxyacetone phosphate (2.5 mM) or 3-phosphoglycerate (2.5 mM) to a suspension of isolated intact chloroplasts, which contains Pi only in low concentrations (0.2 mM) leads to a competitive inhibition of Pi uptake in the light. In consequence, the ATP/ADP ratio is strongly decreased. The rate of O2 evolution is also reduced under these conditions, but the degree of inhibition is much higher after addition of dihydroxyacetone phosphate than after addition of 3-phosphoglycerate. Therefore, besides the competitive inhibition of Pi uptake, additional effects of dihydroxyacetone phosphate and 3-phosphoglycerate on O2 evolution and CO2 fixation of isolated intact chloroplasts must occur, which are discussed.

Adenosine Diphosphate↗
PubMed1980

Characterization and partial purification of dihydroxyacetone kinase in Dunaliella salina.

Dihydroxyacetone kinase from Dunaliella salina is stabilized against inactivation by maintainance in the presence of 2 M glycerol. In the stabilized form a two-step purification procedure resulted in an enzyme preparation of about 440-fold purity which gave three bands (78 000--100 000 daltons) in the absence of denaturing agents on a polyacrylamide gel. The enzyme is specific for dihydroxyacetone and Mg2+-ATP complex as its substrates. It has sharp pH activity curve with pH optimum around 7.5 and little activity below 6. It is suggested that dihydroxyacetone kinase plays a central role in the mechanism of osmoregulation via glycerol in Dunaliella.

Chemical Phenomena↗