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PubMed2000

A sunscreen-tanning compromise: 3D visualization of the actions of titanium dioxide particles and dihydroxyacetone on human epiderm.

The self-tanning agent dihydroxyacetone (DHA) was applied to human skin samples, and its effect on light absorption was followed in time to study the DHA influence inside the different layers of skin. Application of DHA shows increased light absorption in the visible light region, as evidenced by skin tanning. The tanning effect is enhanced by UV irradiation and appears localized in the near-stratum corneum layer as revealed by depth analysis of the time signal. As a reference, application of an emulsion containing titanium dioxide particles shows clear surface stability and a screening of light penetration beyond the stratum corneum.

Dihydroxyacetone↗
PubMed2003

Fluorescence spectral imaging of dihydroxyacetone on skin in vivo.

Dihydroxyacetone (DHA) has been proposed as a potential alternative to dansyl chloride for use as a fluorescence marker on skin to assess stratum corneum turnover time in vivo. However, the fluorescence from DHA on skin has not been adequately studied. To address this void, a noninvasive, noncontact spectral imaging system is used to characterize the fluorescence spectrum of DHA on skin in vivo and to determine the optimal wavelengths over which to collect the DHA signal that minimizes the contributions from skin autofluorescence. The DHA-skin fluorescence signal dominates the 580-680 nm region of the visible spectrum when excited with ultraviolet radiation in the 320-400 nm wavelength region (UVA). An explanation of the time-dependent spectral features is proposed in terms of DHA polymerization and binding to skin.

Diagnostic Imaging↗
PubMed1991

The effect of pyruvate or dihydroxyacetone on parenterally induced liver lipid accumulation in the rat.

Orally fed pyruvate (pyr) and dihydroxyacetone (DHA) have been shown to decrease liver lipid accumulation in animal models. These compounds lessen the degree of fatty liver in ethanol-fed rats and in a genetic strain of hens predisposed to fatty liver. Total parenteral nutrition can result in liver dysfunction, including fatty infiltration of the liver. In this study, rats were assigned to either control, pyr, or DHA groups. All rats were fitted with jugular vein catheters, and following a 3-day recovery, were infused continuously for 7 days. The infusate provided adequate nutrition (including 7% kcal as fat) with 5% pyr or 5% DHA (g/liter) substituted for dextrose in the experimental groups. Plasma triglycerides were lower in the pyr groups relative to controls: 62.2 +/- 34.7 (SE) vs 96.8 +/- 44.3 mg/dl, though this was significant only at P less than 0.10. Neither pyr nor DHA decreased liver lipids. Pyr and DHA were administered intravenously in this study, and therefore passed through the heart and to peripheral tissues first. These compounds may need to be fed orally, passing via the portal system, to produce the liver lipid-lowering effects seen in other studies.

Animals↗
PubMed1997

Reduced dihydroxyacetone sensitivity and normal sensitivity to glyceraldehyde and oxidizing agent of ATP-sensitive K+ channels of pancreatic beta cells in NIDDM rats.

The inhibition of ATP-sensitive K+(KATP) channels in pancreatic beta cells is a key step of insulin secretion induced by glucose. Glucose-induced insulin secretion from the beta cells is selectively impaired in patients with noninsulin-dependent diabetes mellitus (NIDDM) and in animal models of it. In order to clarify the site of this abnormal glucose response, we studied the effects of insulin secretagogues and sulfhydryl oxidizing agent, 2,2'-dithio-bis (5-nitropyridine) (DTBNP), on KATP channels in single beta cells of neonatally streptozotocin-induced NIDDM rats. We used the patch-clamp technique in cell-attached mode (Vpipette = 0 mV). The inhibitory response to glucose of KATP channels was lacking in NIDDM rats, indicating reduced sensitivity to glucose of the channels. Glyceraldehyde (2-5 mM) in the diabetic beta cells elicited the same KATP channel inhibition as that obtained in controls. In contrast, dihydroxyacetone (DHA, 2-10 mM) sensitivity of KATP channels was significantly reduced in the beta cells of NIDDM rats. KATP channels in the diabetic beta cells were rapidly inhibited by 50 microM DTBNP, just as in the normal beta cells, suggesting that KATP channel function was normal. This indicates that one of the sites responsible for impaired glucose-induced insulin secretion in the pancreatic beta cells of NIDDM rats is located in the glycerol phosphate shuttle.

Adenosine Triphosphate↗
PubMed1990

Effect of dihydroxyacetone and pyruvate on plasma glucose concentration and turnover in noninsulin-dependent diabetes mellitus.

Consumption of dihydroxyacetone and pyruvate (DHP) increases muscle extraction of glucose in normal men. To test the hypothesis that these three-carbon compounds would improve glycemic control in diabetes, we evaluated the effect of DHP on plasma glucose concentration, turnover, recycling, and tolerance in 7 women with noninsulin-dependent diabetes. The subjects consumed a 1,500-calorie diet (55% carbohydrate, 30% fat, 15% protein), randomly containing 13% of the calories as DHP (1/1) or Polycose (placebo; PL), as a drink three times daily for 7 days. On the 8th day, primed continuous infusions of [6-3H]-glucose and [U-14C]-glucose were begun at 05.00 h, and at 09.00 h a 3-hour glucose tolerance test (75 g glucola) was performed. Two weeks later the subjects repeated the study with the other diet. The fasting plasma glucose level decreased by 14% with DHP (DHP = 8.0 +/- 0.9 mmol/l; PL = 9.3 +/- 1.0 mmol/l, p less than 0.05) which accounted for lower postoral glucose glycemia (DHP = 13.1 +/- 0.8 mmol/l, PL = 14.7 +/- 0.8 mmol/l, p less than 0.05). [6-3H]-glucose turnover (DHP = 1.50 +/- 0.19 mg.kg-1.min-1, PL = 1.77 +/- 0.21 mg.kg-1.min-1, p less than 0.05) and glucose recycling, the difference in [6-3H]-glucose and [U-14C]-glucose turnover rates, decreased with DHP (DHP = 0.25 +/- 0.07 mg.kg-1.min-1, PL = 0.54 +/- 0.10 mg.kg-1.min-1, p less than 0.05). Fasting and postoral glucose, plasma insulin, glucagon, and C peptide levels were unaffected by DHP.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1980

Selective changes in enzymes of the sn-glycerol 3-phosphate and dihydroxyacetone-phosphate pathways of triacylglycerol biosynthesis during differentiation of 3T3-L1 preadipocytes.

Enzyme activities of the sn-glycerol 3-phosphate (glycerol-P) and of the dihydroxyacetone-phosphte (DHAP) pathway of glycerolipid biosynthesis were investigated during the differentiation of 3T3-L1 preadipocytes into adipocytes. Total particulate glycerol-P and DHAP acyltransferase activities increased 70- and 30-fold, respectively, during differentiation induced with methylisobutylxanthine and dexamethasone. The N-ethylmaleimide-sensitive (microsomal) glycerol-P and DHAP acyltransferase activities were virtually undetectable in nondifferentiated cells, and increased in parallel over 70-fold during differentiation. These and several kinetic observations are consistent with the induction of a single microsomal enzyme having dual activity. During differentiaion, the N-ethylmaleimide-resistant DHAP acyltransferase activity increased 10-fold, suggesting the presence of at least two DHAP acyltransferase isoenzymes. Qualitatively similar changes in microsomal glycerol-P and DHAP acyltransferase activities were observed when cell differentiation was induced with insulin or with insulin plus dexamethasone and methylisobutylxanthine. Acyl-DHAP oxidoreductase (EC 1.1.1.101) specific activity increased only 3- to 5-fold during adipocyte differentiation. Alkyl-DHAP synthase activity was not detected. These data demonstrate that selective changes in enzyme activities of the gycerol-P pathways of glycerolipid synthesis occur during the differentiation of 3T3-L1 preadipocytes.

1-Methyl-3-isobutylxanthine↗
PubMed2003

Stereoselective aldol additions catalyzed by dihydroxyacetone phosphate-dependent aldolases in emulsion systems: preparation and structural characterization of linear and cyclic iminopolyols from aminoaldehydes.

The potential of dihydroxyacetone phosphate (DHAP)-dependent aldolases to catalyze stereoselective aldol additions is, in many instances, limited by the solubility of the acceptor aldehyde in aqueous/co-solvent mixtures. Herein, we demonstrate the efficiency of emulsion systems as reaction media for the class I fructose-1,6-bisphosphate aldolase (RAMA) and class II recombinant rhamnulose-1-phosphate aldolase from E. coli (RhuA)-catalyzed aldol addition between DHAP and N-benzyloxycarbonyl (N-Cbz) aminoaldehydes. The use of emulsions improved the RAMA-catalyzed aldol conversions by three to tenfold relative to those in conventional DMF/water mixtures. RhuA was more reactive than RAMA towards the N-Cbz aminoaldehydes regardless of the reaction medium. With (S)- or (R)-Cbz-alaninal, RAMA exhibited preference for the R enantiomer, while RhuA had no enantiomeric discrimination. The linear N-Cbz aminopolyols thus obtained were submitted to catalytic intramolecular reductive amination to afford the corresponding iminocyclitols. This reaction was diastereoselective in all cases examined; the face selectivity was controlled by the stereochemistry of the newly formed hydroxyl group originating from the aldehyde. Characterization of the resulting iminocyclitols allowed the assessment of the diastereoselectivity of the enzymatic aldol reactions with respect to the N-protected aminoaldehyde. RAMA formed single diastereoisomers from N-Cbz-glycinal and from both enantiomers of N-Cbz-alaninal, while 14 % of the epimeric product was observed from N-Cbz-3-aminopropanal. Diastereoselectivity from RhuA was lower than that observed from RAMA. Interestingly, a single diastereoisomer was formed from (S)-Cbz-alaninal, whereas only a 34 % diastereomeric excess was observed from its enantiomer (i.e., (R)-Cbz-alaninal).

Journal Article↗
PubMed2003

Fragmentation of dihydroxyacetone kinase 1 from Saccharomyces cerevisiae indicates a two-domain structure.

Global protein expression in Saccharomyces cerevisiae strains either deleted for both yeast dihydroxyacetone kinases (DAK1 and DAK2) or overexpressing DAK1, was characterized by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). We found protein expression in the double deletion strain to be highly similar to wild-type. In the strain overexpressing Dak1p, nine spots representing fragments of the Dak1p protein in the size range 40-20 kDa and amounting to approximately 30% of total Dak1p, were discovered (native size Dak1p migrates at roughly 60 kDa). Fragments were characterized by matrix-assisted laser desorption/ionization mass spectrometry and electrospray mass spectrometry analyses to represent either the N- or the C-terminal part of the DAK1 protein. Cleavage points, predicted from mass spectrometry and 2-D PAGE data, mapped almost exclusively in the middle region showing low sequence conservation between Dak1p and its closest homologues. We hypothesize that observed Dak1p fragments represent stable structural domains shielded from access by native endoproteases. Furthermore, overexpressing Dak1p with the non-native N-terminus (M)A-, resulted in native size Dak1p and N-terminal Dak1p fragments appearing in two major 2-D PAGE forms of approximately equal size and abundance, but with slightly different isoelectric points. However, when overexpressing Dak1p with the native N-terminus (M)S-, only the more acidic 2-D PAGE form appeared. In the N-terminal acetyltransferase mutant nat1delta, (M)A-Dak1p species were converted into the basic form, arguing twin spots to represent forms with acetylated and deacetylated N-termini. Data thus indicated that (M)A-N-termini, in the Dak1p context, were NatA substrates recognized with 50% lower efficiency than (M)S-N-termini.

Acetylation↗
PubMed2002

Osmoregulatory isoform of dihydroxyacetone phosphate reductase from Dunaliella tertiolecta: purification and characterization.

The osmoregulatory isoform of dihydroxyacetone phosphate (DHAP) reductase (Osm-DHAPR) is an enzyme unique to Dunaliella, photosynthetic unicellular green algae adapted to extreme environments. This is the first report of purification of an isoform of DHAP reductase from Dunaliella, specifically the osmoregulatory isoform that is involved in the synthesis of free glycerol for osmoregulation in extreme environments, such as high salinity. The Osm-DHAPR is cold labile, inactivated by ammonium sulfate, forms a strong complex with Rubisco, and is unstable in the absence of glycerol. These difficulties have been addressed, and a four-step procedure has been developed to purify the Osm-DHAPR from Dunaliella tertiolecta: precipitation of Rubisco by polyethylene glycol, followed by successive chromatography on DEAE cellulose, Sephacryl S-200, and Red Agarose. Yield of the purified enzyme was 3.6%, with a specific activity of 938 micromol.min-1.mg-1 of protein and a subunit molecular mass of approximately 38 kDa. A maximum specific activity of 2580 micromol.min-1.mg-1 of protein could be achieved by assay with 150 mM NaCl. The Osm-DHAPR had little preference for NADH or NADPH, but it is highly specific for DHAP. Other metabolites of glycolysis, the tricarboxylic acid cycle, and the C3 reductive photosynthetic carbon cycle were not reduced by the enzyme. The purified enzyme was stimulated three-fold by 150 to 250 mM NaCl/KCl and by 25 mM MgCl2. Detergents, lipids, or long-chain acyl CoA derivatives, all of which inhibited the chloroplastic glyceride form of DHAP reductase, did not affect the activity of Osm-DHAPR. The Osm-DHAPR has different properties than the other chloroplastic isoform of DHAP reductase from plants and algae for glycerol phosphate formation and triglyceride synthesis.

Chlorophyta↗
PubMed1989

Biosynthesis of the peroxisomal dihydroxyacetone synthase from Hansenula polymorpha in Saccharomyces cerevisiae induces growth but not proliferation of peroxisomes.

The DAS gene of Hansenula polymorpha was expressed in Saccharomyces cerevisiae under the control of different promoters. The heterologously synthesized dihydroxyacetone synthase (DHAS), a peroxisomal enzyme in H. polymorpha, shows enzymatic activity in baker's yeast. The enzyme was imported into the peroxisomes of S. cerevisiae not only under the appropriate physiological conditions for peroxisome proliferation (oleic acid media), but also in glucose-grown cells where it induced the enlargement of the few peroxisomes present. This growth process was not accompanied by an increase in the number of microbodies, which suggests a separate control mechanism for peroxisomal proliferation.

Alcohol Oxidoreductases↗
PubMed1995

Measurement of dihydroxyacetone-phosphate acyltransferase (DHAPAT) in chorionic villous samples, blood cells and cultured cells.

Dihydroxyacetone-phosphate acyltransferase (DHAPAT) is a peroxisomal enzyme catalysing the first step in ether-phospholipid biosynthesis. DHAPAT is deficient in cells from patients suffering from a variety of peroxisomal disorders. Accurate measurement of the activity of this enzyme is of great importance, especially since it is a central parameter in the prenatal diagnosis of the disorders of peroxisome biogenesis, rhizomelic chondrodysplasia punctata and DHAPAT-deficiency. We describe a straightforward and accurate assay allowing the activity of DHAPAT to be measured reliably in chorionic villus samples, blood cells, cultured skin fibroblasts, cultured chorionic villus fibroblasts and cultured amniocytes.

Acyltransferases↗
PubMed1986

Partial deficiency of dihydroxyacetone phosphate acyltransferase activity in both classical and infantile Refsum's diseases.

We measured the activity of dihydroxyacetone phosphate acyltransferase (DHAP-AT) in fibroblasts of controls and patients with classical Refsum's disease (RD), infantile Refsum's disease (IRD) and Zellweger's syndrome (ZS). We confirmed that DHAP-AT activity is severely reduced in ZS fibroblasts and amniocytes. We also demonstrated a partial deficiency of DHAP-AT activity in RD and IRD fibroblast cultures. These diseases are probably distinct but related entities in which peroxisomal biogenesis is affected to varying degrees.

Acyltransferases↗
PubMed1998

The Hansenula polymorpha per6 mutant is affected in two adjacent genes which encode dihydroxyacetone kinase and a novel protein, Pak1p, involved in peroxisome integrity.

The Hansenula polymorpha per6-210 mutant is impaired in respect of growth on methanol (Mut-) and is characterized by aberrant peroxisome formation. The functionally complementing DNA fragment contains two open reading frames. The first encodes dihydroxyacetone kinase (DAK), a cytosolic enzyme essential for formaldehyde assimilation; the second ORF codes for a novel protein (Pak1p). We have demonstrated that per6-210 cells lack DAK activity, causing the Mut- phenotype, and have strongly reduced levels of Pak1p, resulting in peroxisomal defects. Sequence analysis revealed that per6-210 contains a mutation in the 3' end of the DAK coding region, which overlaps with the promoter region of PAK1. Possibly this mutation also negatively affects PAK1 expression.

Amino Acid Sequence↗
PubMed1986

Subcellular distribution and properties of acyl/alkyl dihydroxyacetone phosphate reductase in rodent livers.

On subcellular fractionation, the enzyme acyl/alkyl dihydroxyacetone phosphate (DHAP) reductase (EC 1.1.1.101) in guinea pig and rat liver was found to be present in both the light mitochondrial (L) and microsomal fractions. By using metrizamide density gradient centrifugation, it was shown that the alkyl DHAP reductase activity in the "L" fraction is localized mainly in peroxisomes. From the distribution of the marker enzymes it was calculated that about two-thirds of the liver reductase activity is in the peroxisomes and the rest in the microsomes. The properties of this enzyme in peroxisomes and microsomes are similar with respect to heat inactivation, pH optima, sensitivity to trypsin, and inhibition by NADP+ and acyl CoA. The enzyme activity in the peroxisomes and microsomes from mouse liver is increased to the same extent by chronically feeding the animals clofibrate, a hypolipidemic drug. The kinetic properties of this enzyme in these two different organelles are also similar. From these results it is concluded that the same enzyme is present in two different subcellular compartments of liver.

Animals↗
PubMed1989

Dihydroxyacetone phosphate acyltransferase and alkyldihydroxyacetone phosphate synthase activities in rat liver subcellular fractions and human skin fibroblasts.

Dihydroxyacetone phosphate acyltransferase (DHAP-AT) and alkyldihydroxyacetone phosphate synthase (DHAP-synthase) activities were examined in subcellular fractions of rat liver. The results indicate that at least 80% of DHAP-AT (assays carried out at pH 5.4) activity in rat liver is in peroxisomes, and the remaining activity is mitochondrial. In contrast to DHAP-AT, DHAP-synthase was detected in all subcellular fractions analyzed but the activity in peroxisomes was 208-fold and 42-fold greater compared to mitochondria and microsomes, respectively. We estimate that at least 70% of the DHAP-synthase activity in rat liver is in peroxisomes. DHAP-AT and DHAP-synthase activities were also examined in homogenates of skin fibroblasts from patients with inherited defects in peroxisomal structure and/or function. Both the enzyme activities were deficient in Zellweger syndrome whereas the activities were only partially deficient in infantile Refsum's disease. Greater reduction in DHAP-synthase activity, but only a partial reduction in DHAP-AT activity was observed in rhizomelic chondrodysplasia punctata. However, both DHAP-AT and DHAP-synthase activities were either normal or near normal in Refsum's disease or X-linked adrenoleukodystrophy. The results reported suggest that various peroxisomal disease states can be identified based on DHAP-AT and DHAP-synthase activities in skin fibroblasts of patients.

Acyltransferases↗
PubMed1988

Rat liver dihydroxyacetone-phosphate acyltransferase: enzyme characteristics and localization studies.

Peroxisomes were isolated from rat liver by pelleting a light mitochondrial (L) fraction over a 30% (w/v) Metrizamide layer. Peroxisomes were recovered as a loose pellet from the bottom of the tube and the purity of the peroxisomal fraction was calculated to be about 90%. The characteristics of dihydroxyacetone-phosphate acyltransferase (DHAP-AT) in the light mitochondrial fraction and the purified peroxisomal fraction were compared. The behaviour of the enzyme in the two fractions was very similar, except for the effect of sodium fluoride, which stimulated the activity in the L fraction 5-10-fold and in the peroxisomal fraction only 1.6-fold. This difference could be explained by the action of fluoride-sensitive acid phosphatases present in the L fraction that dephosphorylate palmitoyl-coenzyme A, a substrate for DHAP-AT. The localizations of DHAP-AT and alkyldihydroxyacetone-phosphate synthase in the rat liver peroxisomal membrane were studied. It is shown that in intact peroxisomes, DHAP-AT and alkyl-DHAP synthase are resistant to proteolytic inactivation by trypsin, as is fatty acid beta-oxidation activity, which served as a marker for the intactness of the peroxisomal membrane. Catalase was found not to be a suitable marker to assess peroxisome intactness in view of its relative insensitivity to trypsin. In 1-lauroyllysophosphatidylcholine-permeabilized peroxisomes, DHAP-AT, alkyl-DHAP synthase and beta-oxidation activities were rapidly inactivated by trypsin. It is concluded that in rat liver peroxisomes, at least the active sites of the integral membrane proteins DHAP-AT and alkyl-DHAP synthase are localized exclusively at the inner surface of the peroxisomal membrane.

Acyltransferases↗
PubMed1990

Changes in the activities of dihydroxyacetone phosphate and glycerol-3-phosphate acyltransferases in rat liver under various conditions.

Activities of enzymes relating to the acyl dihydroxyacetone phosphate (acyl DHAP) pathway were determined in rat liver under conditions known to elevate the peroxisomal beta-oxidation activity. In fasted and streptozotocin-induced diabetic rats, DHAP acyltransferase activity showed a small but significant increase, though the activities of glycerol-3-phosphate (GP) acyltransferase and alkyl DHAP synthase were not changed. After 2 weeks, feeding of 20% partially hydrogenated marine oil, the activity of DHAP acyltransferase also increased to 140% of the control. The feeding of 0.25% clofibrate and 2% di(2-ethylhexyl)phthalate (DEHP) increased the activities of both DHAP and GP acyltransferases by 2- to 3-fold, whereas alkyl DHAP synthase activity decreased under the same conditions. A fractionation study showed that the increases in the activities of DHAP acyltransferase and acyl/alkyl DHAP reductase in the liver of rats treated with DEHP occurred mainly in peroxisomes and microsomes, respectively. The phospholipid contents per mg protein of the isolated hepatic peroxisomes from rats were as follows (percent of the control): fasting, 62%; diabetic, 69%; high fat-diet, 89%; clofibrate-treated, 126%; DEHP-treated, 119%. These results suggest that glycerophospholipid metabolism might also be controlled by peroxisomal enzymes under physiological and pathological conditions.

Acyltransferases↗
PubMed1984

Deficiency of acyl-CoA: dihydroxyacetone phosphate acyltransferase in patients with Zellweger (cerebro-hepato-renal) syndrome.

We have recently reported on plasmalogen deficiency in tissues and fibroblasts from patients with Zellweger syndrome. In this paper we have analyzed the activity of the first enzyme in the pathway leading to plasmalogen biosynthesis, i.e. acyl-CoA:dihydroxyacetone phosphate acyltransferase in liver, brain and cultured skin fibroblasts from Zellweger patients and controls. The results indicate a severe deficiency of this enzyme in Zellweger patients. Thus, the Zellweger syndrome constitutes the first inborn error of metabolism with a deficiency in an enzyme involved in phospholipid biosynthesis. Cultured amniotic fluid cells contained an enzymatic activity comparable to that of control fibroblasts. These findings suggest a method for prenatal diagnosis of this disease.

Acyltransferases↗