Acylation of glycerol‐3‐phosphate by rabbit heart mitochondria and microsomes: Triiodothyronine‐induced increase in its activity

Kako, K. J.; Liu, M.S.

doi:10.1016/0014-5793(74)80060-8

Cited by 19 publications

(3 citation statements)

References 18 publications

(7 reference statements)

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“…In an early study of the effects of altered thyroid status on diglyceride acyltransferase activity, Young and Lynen (106) observed that T 3 treatment of rats increased its specific activity in hepatic microsomes, while administration of PTU decreased the activity. Similar observations have been reported for the cardiac enzyme (109,110). A regulatory role of phosphatidate phosphohydrolase in glycerolipid synthesis has been proposed on the basis of the observations that this enzyme responds more readily and dramatically than the other enzymes of glycerolipid synthesis to altered physiological (111)(112)(113)(114) and pharmacological (115)(116)(117)(118) stimuli imposed on the animal, and the changes have been shown to parallel closely the capacity of the liver to synthesize TG in vitro in cellfree systems (112,118,119).…”

Section: Synthesis and Secretion Of Tg And The Vldlmentioning

confidence: 54%

Plasma Lipoproteins and Regulation of Hepatic Metabolism of Fatty Acids in Altered Thyroid States*

1985

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This article reviews our understanding of effects of thyroid hormone excess and deficiency on hepatic metabolism of FFA, and consequent effects on production, secretion, and metabolism of plasma lipoproteins. In the hyperthyroid state the following alterations are observed. Fatty acid oxidation and ketogenesis are stimulated simultaneously with a paradoxical stimulation of fatty acid synthesis, which may be linked by virtue of a blunted response of mitochondrial carnitine palmitoyltransferase I (CPT-I) to malonyl coenzyme A (CoA). Esterification of fatty acid to triglyceride (TG) is reduced, as is the secretion of the very low density lipoprotein (VLDL) (including VLDL TG, cholesterol, and apoprotein); this may be due, in part, to decreased concentrations of glycerol-3-phosphate (G3P) in the hepatic cell. In the intact animal or patient, however, serum TG concentration is variable, which may reflect increased adipose tissue lipolysis and elevated concentrations of plasma FFA, which would tend to drive VLDL secretion by the liver. Clearance of the VLDL and its metabolic product, the low density lipoprotein (LDL), is increased, resulting in decreased plasma total and LDL cholesterol. Although high density lipoprotein (HDL) cholesterol may also be reduced, the ratio of LDL/HDL cholesterol is further decreased. The regulatory role of the lipoprotein apoproteins is less clear, but hepatic apolipoprotein (apo) B secretion (required for VLDL) is diminished, while apo-AI secretion (required for HDL) is stimulated, perhaps both reflecting rates of synthesis. Plasma concentrations of apo-AI are variable, dependent on relative rates of secretion and clearance. In the hypothyroid, many of these effects are reversed, which results in hyperlipoproteinemias and greater risk for the development of atherosclerotic cardiovascular disease.

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Section: Synthesis and Secretion Of Tg And The Vldlmentioning

confidence: 54%

Plasma Lipoproteins and Regulation of Hepatic Metabolism of Fatty Acids in Altered Thyroid States*

1985

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“…It has been found that both Escherichia coli (3,4) and hepatic mitochondrial and microsomal fractions (5-9) contain these two enzymes and that monoacylglycerol 3-phosphate (P) is the product of the first and the substrate of the second reaction. We have investigated the properties of these enzymes of the subcellular fractions of rabbit hearts (10)(11)(12)(13). The kinetics, substrate preference, and products of these enzymes reactions were studied in previous reports.…”

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confidence: 99%

Effect of bovine serum albumin on monoacyl‐ and diacylglycerol 3‐phosphate formation in mitochondrial and microsomal fractions of rabbit hearts

Zaror-Behrens

Kako

1976

Lipids

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The formation of monoacyl- and diacylglycerol 3-phosphate (P) by rabbit heart mitochondrial and microsomal fractions was studied by varying the concentration of acyl-CoA and that of bovine serum albumin in the assay system. The two subcellular fractions were prepared by the conventional differential centrifugation technique. The optimal concentration of acyl-CoA for both mitochondrial and microsomal acylation of glycerol 3-P was shifted to a higher range of acyl-CoA concentrations by greater amounts of albumin. A similar shift in the acyl-CoA concentration-enzyme activity relationship was observed in the acylation reaction of 1-palmitoylglycerol 3-P by the heart microsomes. The addition of albumin increased slightly the rate of diacylglycerol 3-P accumulation but increased greatly the rate of monoacylglycerol 3-P accumulation at any concentration of acyl-CoA; the effect was observed with mitochondrial or microsomal fraction as the crude enzyme source. Moreover, palmitoyl-CoA and linoleoyl-CoA served equally well as the acyl donor for the acylation reaction. However, relatively more monoacyl- than diacylglycerol 3-P was accumulated in the assays with rabbit heart mitochondrial fraction in the presence of albumin, whereas more diacyl- than monoacylglycerol 3-P was formed by the microsomal fraction. As a result, the microsomal diacyl:monoacyl-glycerol 3-P ratio was invariably greater than the mitochondrial ratio at a given concentration of acyl-CoA and albumin.

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“…All of these used differential centrifugation to separate subcellular fractions. Acyltransferase enzymes from rat liver (14,23), rabbit lung (6), and rabbit heart (8) were shown to be localized largely in the microsomal fraction (10,000-100,OOOg pellet), but were also present in the mitochondrial preparations. The mitochondrial enzyme usually differed from the microsomal enzyme by catalyzing a single acylation of sn-glycerol-3-P to form monoacyl-sn-glycerol-3-P (lysophosphatidic acid), while the microsomal fractions were able to acylate both hydroxyls to give phosphatidic acid.…”

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confidence: 99%

Phosphatidic Acid Synthesis in Castor Bean Endosperm

Vick

Beevers²

1977

Plant Physiol.

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Enzyme assays on organelles isolated from the endosperm of castor bean (Ricinus communis var. Hale) by sucrose density gradient centrifugation showed that palmitoyl-CoA sn-glycerol 3-phosphate acyltransferase (EC 2.3.1.15) was localized in the membranes of the endoplasmic reticulum. Mn2+ was required for activity, but Ca2+ and Mg2+ could substitute for Mn2+ at higher concentrations. The apparent Km was 170,LM for sn-glycerol 3-phosphate and approximately 8 ,UM for palmitoylCoA. The optimum pH range was 7 to 7.5 and the principal reaction product was diacyl-sn-glycerol 3-phosphate (phosphatidic acid). Monoacyl-sn-glycerol 3-phosphate (lysophosphatidic acid) was not released as a free intermediate in the reaction. The maximum activity of the enzyme occurred immediately after imbibition, preceding the development of mitochondria and glyoxysomes.The acylation of sn-glycerol-3-P is a fundamental reaction in the synthesis of complex lipids in animals (9), plants (3,13,22), and bacteria (19). Acyl-CoA is the acyl donor in animals and plants, in some bacteria the acyl donor is acyl-ACP (12), and in Escherichia coli (21) either donor may function. In rat liver microsomal preparations (23) and in E. coli (18), the acylation has been shown to occur as two distinct reactions, with 1-acyl-snglycerol-3-P as the product of the first acylation, and 1,2-diacylsn-glycerol-3-P (phosphatidic acid) as the product of the second. The reactions are catalyzed by acyltransferase(s) and are of particular interest because the final product, phosphatidic acid, serves as a precursor to all of the phospholipid constituents of membranes as well as the di-and triacylglycerols.Because of its importance in membrane biogenesis, the intracellular site of acyltransferase activity has been examined by several investigators. All of these used differential centrifugation to separate subcellular fractions. Acyltransferase enzymes from rat liver (14, 23), rabbit lung (6), and rabbit heart (8) were shown to be localized largely in the microsomal fraction (10,000-100,OOOg pellet), but were also present in the mitochondrial preparations. The mitochondrial enzyme usually differed from the microsomal enzyme by catalyzing a single acylation of sn-glycerol-3-P to form monoacyl-sn-glycerol-3-P (lysophosphatidic acid), while the microsomal fractions were able to acylate both hydroxyls to give phosphatidic acid. In plants, Cheniae (3) demonstrated that "microsomal-like particles" from spinach leaves were able to catalyze the incorporation of snglycerol-3-P into phosphatidic acid. Sastry and Kates (22), also working with spinach leaves, found essentially the same results, but acknowledged that their microsomal preparation may have contained some mitochondria and grana. Macher et al. (13) used crude extracts of etiolated cucumber cotyledons to study snglycerol-3-P incorporation into phosphatidic acid. Except for I This work was supported by Contract E(04-3)34 from ERDA. these reports, little is known about the properties of the acyltransferase enzyme in plan...

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Acylation of glycerol‐3‐phosphate by rabbit heart mitochondria and microsomes: Triiodothyronine‐induced increase in its activity

Cited by 19 publications

References 18 publications

Plasma Lipoproteins and Regulation of Hepatic Metabolism of Fatty Acids in Altered Thyroid States*

Plasma Lipoproteins and Regulation of Hepatic Metabolism of Fatty Acids in Altered Thyroid States*

Effect of bovine serum albumin on monoacyl‐ and diacylglycerol 3‐phosphate formation in mitochondrial and microsomal fractions of rabbit hearts

Phosphatidic Acid Synthesis in Castor Bean Endosperm

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