Dihydroxyacetone Phosphate Acyltransferase Activity Research Articles

Effects of chronic modification of dietary fat and carbohydrate in rats.

1. Rats were fed on diets enriched with starch, sucrose, corn oil or beef tallow for 3 weeks and the activities of various enzymes in the liver were measured. 2. The mitochondrial glycerol phosphate acyltransferase activity was lower in rats fed on the starch diet than on the two high-fat diets. 3. The non-microsomal (presumably peroxisomal) dihydroxyacetone phosphate acyltransferase activity was higher in rats fed on the starch diet and corn-oil diets than in those fed on the sucrose and beef-tallow diets. Urate oxidase activity was higher in rats fed on the starch diet than in the three other groups. There were no significant differences in the activity of acyl-CoA oxidase among the groups. 4. The activity of soluble phosphatidate phosphohydrolase was not significantly different among the dietary groups. There were increases of 3.3--4.3-fold in this activity in the dietary groups 6h after injection of corticotropin. The equivalent increases for the mitochondrial glycerol phosphate acyltransferase were 1.4--1.6 fold. 5. The corticosterone responses to the corticotropin injection were not significantly different between dietary groups. However, the corticosterone response of the rats fed on the two high-fat diets was prolonged when the rats were given an acute load of fructose [Brindley, Cooling, Glenny, Burditt & McKechnie (1981) Biochem. J. 200. 275--283]. 6. Rats fed on the high-fat diets had higher concentrations of circulating cholesterol than those fed on the starch and sucrose diets. Serum triacylglycerol concentrations were lower in the rats fed on the starch diet than in the three other groups. 7. The results are discussed in terms of the relationship between diet, hormonal balance and hepatic glycerolipid metabolism.

Effects of adrenalectomy and cortisol treatment on dihydroxyacetone phosphate acyltransferase activity in rat liver

Currently it is thought that the biosynthesis of glycerolipids is initiated by the acylation of glycerol phosphate or dihydroxyacetone phosphate. The relative contributions of these two metabolic routes are not fully established (reviewed in [I]). There is believed to be a peroxisomal dihydroxyacetone phosphate acyltransferase (DHAPAT) activity in liver [2,3] although on subcellular fractionation DHAPAT activity is also found in mitochondria and microsomes. Glycerol phosphate acyltransferase (GPAT) activity is found in both mitochondrial and microsomal fractions (reviewed in [4]). We have shown that mitochondrial GPAT activity is decreased by adrenalectomy in both fed and fasted animals [5]. Microsomal GPAT activity was decreased by adrenalectomy in fasted animals only [S]. These results show the effects of adrenalectomy and cortisol injection on hepatic DHAPAT activity.

A study of the glycerol phosphate acyltransferase and dihydroxyacetone phosphate acyltransferase activities in rat liver mitochondrial and microsomal fractions. Relative distribution in parenchymal and non-parenchymal cells, effects of N-ethylmaleimide, palmitoyl-coenzyme A concentration, starvation, adrenalectomy and anti-insulin serum treatment.

1. GPAT (glycerol phosphate acyltransferase) and DHAPAT (dihydroxyacetone phosphate acyltransferase) activities were measured both in subcellular fractions prepared from fed rat liver and in whole homogenates prepared from freeze-stopped pieces of liver. 2. GPAT activity in mitochondria differed from the microsomal activity in that it was insensitive to N-ethylmaleimide, had a higher affinity towards the palmitoyl-CoA substrate and showed a different response to changes in hormonal and dietary status. 3. Starvation (48 h) significantly decreased mitochondrial GPAT activity. The ratio of mitochondrial to microsomal activities was also significantly decreased. The microsomal activity was unaffected by starvation, except after adrenalectomy, when it was significantly decreased. Mitochondrial GPAT activity was decreased by adrenalectomy in both fed and starved animals. 4. Acute administration of anti-insulin serum significantly decreased mitochondrial GPAT activity after 60 min without affecting the microsomal activity. 5. A new assay is described for DHAPAT. The subcellular distribution of this enzyme differed from that of GPAT. The highest specific activity of DHAPAT was found in a 23 000 gav. pellet obtained by centrifugation of a post-mitochondrial supernatant. This fraction also contained the highest specific activity of the peroxisomal marker uricase. DHAPAT activity in mitochondrial fractions or in the 23 000 gav. pellet was stimulated by N-ethylmaleimide, whereas that in microsomal fractions was slightly inhibited by this reagent. The GPAT and DHAPAT activities in mitochondrial fractions had a considerably higher affinity for the palmitoyl-CoA substrate. 6. Total liver DHAPAT activity was significantly decreased by starvation (48 h), but was unaffected by administration of anti-insulin serum. 7. The specific activities of GPAT and DHAPAT were lower in non-parenchymal cells compared with parenchymal cells, but the GPAT/DHAPAT ratio was 5--6-fold higher in the parenchymal cells.

Effects of starvation and adrenaline on glycerophosphate acyltransferase and dihydroxy acetone phosphate acyltransferase activities in rat adipocytes

Effects of starvation and adrenaline on glycerophosphate acyltransferase and dihydroxy acetone phosphate acyltransferase activities in rat adipocytes

Glycerolipid biosynthesis in Saccharomyces cerevisiae: sn-glycerol-3-phosphate and dihydroxyacetone phosphate acyltransferase activities.

Yeast acyl-coenzyme A:dihydroxyacetone-phosphate O-acyltransferase (DHAP acyltransferase; EC 2.3.1.42) was investigated to (i) determine whether its activity and that of acyl-coenzyme A:sn-glycerol-3-phosphate O-acyltransferase (glycerol-P acyltransferase; EC 2.3.1.15) represent dual catalytic functions of a single membranous enzyme, (ii) estimate the relative contributions of the glycerol-P and DHAP pathways for yeast glycerolipid synthesis, and (iii) evaluate the suitability of yeast for future genetic investigations of the eucaryotic glycerol-P and DHAP acyltransferase activities. The membranous DHAP acyltransferase activity showed an apparent Km of 0.79 mM for DHAP, with a Vmax of 5.3 nmol/min per mg, whereas the glycerol-P acyltransferase activity showed an apparent Km of 0.05 mM for glycerol-P, with a Vmax of 3.4 nmol/min per mg. Glycerol-P was a competitive inhibitor (Ki, 0.07 mM) of the DHAP acyltransferase activity, and DHAP was a competitive inhibitor (Ki, 0.91 mM) of the glycerol-P acyltransferase activity. The two acyltransferase activities exhibited marked similarities in their pH dependence, acyl-coenzyme A chain length preference and substrate concentration dependencies, thermolability, and patterns of inactivation by N-ethylmaleimide, trypsin, and detergents. Thus, the data strongly suggest that yeast glycerol-P and DHAP acyltransferase activities represent dual catalytic functions of a single membrane-bound enzyme. Furthermore, since no acyl-DHAP oxidoreductase activity could be detected in yeast membranes, the DHAP pathway for glycerolipid synthesis may not operate in yeast.

Microsomal sn-glycerol 3-phosphate and dihydroxyacetone phosphate acyltransferase activities from liver and other tissues : Evidence for a single enzyme catalyzing both reactions

In vitro characterizations of rat liver microsomal acyl-CoA: sn-glycerol 3-phosphate acyltransferase (EC 2.3.1.15) (glycerol-P acyltransferase) and acyl-CoA:dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42) (DHAP acyltransferase) activities were performed in order to test the hypothesis that these two activities in liver microsomes may be dual functions of a single enzyme and to estimate the relative contributions of the glycerol-P and DHAP pathways for hepatic microsomal glycerolipid synthesis. The microsomal glycerol-P acyltransferase activity showed an apparent K m of 0.14 m m for glycerol-P with a V of 2.8 nmol/min/mg, while the DHAP acyltransferase activity showed an apparent K m of 0.3 m m for DHAP with a V of 0.62 nmol/min/mg. Glycerol-P was a competitive inhibitor ( K i = 0.12 mM) of the DHAP acyltransferase activity, and DHAP was a competitive inhibitor ( K i = 1.4 mM) of the glycerol-P acyltransferase activity. The two acyltransferase activities showed great similarities in their pH dependence, acyl-CoA chain length and concentration dependencies, thermolability, and patterns of inactivation by N-ethylmaleimide, trypsin, and detergents. Taken as a whole the data strongly suggest that liver microsomal glycerol-P and DHAP acyltransferase activities actually represent dual catalytic functions of a single microsomal enzyme. Similar kinetic and inhibition studies indicate that this finding is also valid for the two acyltransferase activities from intestinal mucosa, lung, kidney, and brain. Calculations based on the above kinetic constants and previously reported glycerol-P and DHAP pools in liver suggest that the in vivo ratio of glycerol-P to DHAP acylation in liver microsomes should be greater than 84:1.

The effects of diet on the esterification of glycerol phosphate, dihydroxyacetone phosphate and 2-hexadecylglycerol by homogenates of rat adipose tissue

1. Male rats were fed for 5 weeks after weaning on a diet containing (by weight) 59% of starch or on diets that contained 39% of starch and 20% of either sucrose, beef tallow or corn oil. 2. The rats fed on the beef tallow consumed more energy than did the rats fed on the starch and sucrose diets. The rats fed on the corn oil drank less water than did the other groups of rats. 3. There were no significant differences between the four groups in terms of body-weight gain, epididymal-fat-pad weight and in the size, number and triacylglycerol content of the adipocytes in the fat-pads. 4. There was a significant correlation (P less than 0.001) between the activities of glycerol phosphate acyltransferase and monoacylglycerol acyltransferase in individual rats. Both of these activities were highest in the group fed on the high-starch diet and both correlated with the consumption of glucose by individual rats in the four groups. 5. The percentage of glycerol phosphate converted into diacylglycerol and triacylglycerol was positively correlated with the mean diameters, surface area and triacylglycerol content of the adipocytes for individual rats and was greates in the sucrose-fed rats. 6. The specific activity of dihydroxyacetone phosphate acyltransferase was highest in the rats fed on beef tallow. This activity was positively correlated with the energy intake for all dietary groups over the 5-week feeding period. 7. The results are discussed in terms of the functions of the three routes of glycerolipid synthesis in adipose tissue.

Triacylglycerol synthesis in isolated fat cells. Evidence that the sn-glycerol-3-phosphate and dihydroxyacetone phosphate acyltransferase activities are dual catalytic functions of a single microsomal enzyme.

The acyl-CoA:sn-glycerol-3-phosphate acyltransferase (EC 2.3.1.15) (glycerol-P acyltransferase) and acyl-CoA:dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42) (DHAP acyltransferase) activities were investigated in vitro in order to evaluate the quantitative contribution of the glycerol-P and DHAP pathways for the synthesis of triacylglycerols in isolated fat cells and to test the hypothesis that these two activities may be dual catalytic functions of a single enzyme. More than 85% of both acyltransferase activities was associated with the microsomal subcellular fraction. The microsomal glycerol-P acyltransferase activity showed an apparent Km of 8 muM for glycerol-P with a Vmax of 15.6 nmol/min/mg, while the DHAP acyltransferase activity showed an apparent Km of 40 muM for DHAP with a Vmax of 9.7 nmol/min/mg. Glycerol-P was a competitive inhibitor (Ki = 7.2 muM) of the DHAP acyltransferase, and DHAP was a competitive inhibitor (Ki = 92 muM) of the glycerol-P acyltransferase. The two acyltransferase activities showed virtual identity in their pH dependence, acyl-CoA chain length dependence, thermolability, and inactivation by N-ethylmaleimide. Trypsin, detergents, collagenase, phospholipases, and various salts and organic solvents also had similar effects on both activities. Taken as a whole, the data strongly suggest that the microsomal glycerol-P and DHAP acyltransferase activities actually represent dual functions of a single enzyme. Calculations based on the above kinetic constants and previously reported glycerol-P and DHAP pools in adipocytes suggest that the in vivo ratio of glycerol-P to DHAP acylation should be greater than 24:1.

Effect of adrenalcortical hormones on release of triglycerides and glucose by liver.

ARTICLESEffect of adrenalcortical hormones on release of triglycerides and glucose by liverH Klausner, and M HeimbergH Klausner, and M HeimbergPublished Online:01 Jun 1967https://doi.org/10.1152/ajplegacy.1967.212.6.1236MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByHepatocyte-specific glucose-6-phosphatase deficiency disturbs platelet aggregation and decreases blood monocytes upon fasting-induced hypoglycemiaMolecular Metabolism, Vol. 53Variation in glucocorticoid levels in relation to direct and third-party interactions in a social cichlid fishPhysiology & Behavior, Vol. 151Glucocorticoid receptor haploinsufficiency causes hypertension and attenuates hypothalamic‐pituitary‐adrenal axis and blood pressure adaptions to high‐fat diet12 August 2008 | The FASEB Journal, Vol. 22, No. 11Metabolic action of peroxisome proliferator-activated receptor γ agonism in rats with exogenous hypercorticosteronemia19 June 2007 | International Journal of Obesity, Vol. 31, No. 1111β-HSD1 inhibition improves triglyceridemia through reduced liver VLDL secretion and partitions lipids toward oxidative tissuesMagalie Berthiaume, Mathieu Laplante, William T. 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Mecanismo de açãoArquivos de Neuro-Psiquiatria, Vol. 26, No. 4Liver regeneration after partial hepatectomy in rats exposed before the operation to the stress stimulusExperientia, Vol. 24, No. 11Effects of a corticoid on lipid metabolism and on urea formation in isolated rat liverMetabolism, Vol. 17, No. 9 More from this issue > Volume 212Issue 6June 1967Pages 1236-1246 Copyright & PermissionsCopyright © 1967 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1967.212.6.1236PubMed4952109History Published online 1 June 1967 Published in print 1 June 1967 Metrics