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At least 847 records · Page 47Linked to original sources
PubMed1976

Fatty acid binding protein. Role in esterification of absorbed long chain fatty acid in rat intestine.

Fatty acid binding protein (FABP) is a protein of 12,000 mol wt found in cytosol of intestinal mucosa and other tissues, which exhibits high affinity for long chain fatty acids. It has been suggested that FABP (which may comprise a group of closely related proteins of 12,000 mol wt) participates in cellular fatty acid transport and metabolism. Although earlier findings were consistent with this concept, the present studies were designed to examine its physiological function more directly. Everted jejunal sacs were incubated in mixed fatty acid-monoglyceride-bile acid micelles, in the presence or absence of equimolar concentrations of either of two compounds which inhibit oleate binding to FABP:flavaspidic acid-N-methyl-glucaminate and alpha-bromopalmitate. Oleate uptake, mucosal morphology, and oxidation of [14C]acetate remained unaffected by these agents, but oleate incorporation into triglyceride was inhibited by 62-64% after 4 min. The inhibition by flavaspidic acid was reversible with higher oleate concentrations. The effect of these compounds on enzymes of triglyceride biosynthesis was examined in intestinal microsomes. Neither flavaspidic acid nor alpha-bromopalmitate inhibited acyl CoA:monoglyceride acyl-transferase. Fatty acid:coenzyme A ligase activity was significantly enhanced in the presence of partially purified FABP, probably reflecting a physical effect on the fatty acid substrate or on the formation of the enzyme-substrate complex. Activity of the enzyme in the presence of 0.1 mM oleate was only modestly inhibited by equimolar flavaspidic acid and alpha-bromopalmitate, and this effect was blunted or prevented by FABP. We conclude that in everted gut sacs, inhibition of triglyceride synthesis by flavaspidic acid and alpha-bromopalmitate could not be explained as an effect on fatty acid uptake or on esterifying enzymes in the endoplasmic reticulum but rather can be interpreted as reflecting inhibition of fatty acid binding to FABP. These findings lend further support to the concept that FABP participates in cellular fatty acid transport and metabolism. It is also possible that FABP, by effecting an intracellular compartmentalization of fatty acids and acyl CoA, may play a broader role in cellular lipid metabolism.

Acids↗
PubMed1989

The reactivity of desmosterol and other shellfish- and xanthomatosis-associated sterols in the macrophage sterol esterification reaction.

The acyl-CoA: cholesterol acyl transferase (ACAT) reaction in macrophages is a critical step in atherosclerotic foam cell formation, but little is known about the reaction's sterol substrate specificity. In this report we examine the macrophage ACAT reactivity of the shellfish sterol, desmosterol, and other sterols found in man because of shellfish ingestion or in association with the foam cell diseases sitosterolemia and cerebrotendinous xanthomatosis (CTX). We first show that the J774 macrophage, a foam cell model with a hyperactive ACAT pathway, synthesizes desmosterol instead of cholesterol and that both endogenous and exogenous desmosterol are substrates and stimulators of the ACAT reaction in these cells. When exogenous desmosterol was added to human monocyte-derived macrophages, ACAT was stimulated 29- and 4-fold compared with control and cholesterol-treated cells, respectively. Steryl ester mass accumulation in desmosterol-treated human macrophages was 10-fold greater than in control cells and 3-fold greater than in cholesterol-treated cells. Another shellfish sterol, 24-methylene cholesterol, also stimulated ACAT in human macrophages, but most of the xanthomatosis-related sterols did not stimulate ACAT. These data suggest that: (a) the shellfish sterols desmosterol and 24-methylene cholesterol may be atherogenic; and (b) the excessive foam cell formation seen in sitosterolemia and CTX cannot be explained by ACAT hyperreactivity of their associated sterols.

Animals↗
PubMed2003

Decreased fatty acid esterification compensates for the reduced lipolytic activity in hormone-sensitive lipase-deficient white adipose tissue.

It has been observed previously that hormone-sensitive lipase-deficient (HSL-ko) mice have reduced white adipose tissue (WAT) stores compared to control mice. These findings contradict the expectation that the decreased lipolytic activity in WAT of HSL-ko mice would cause accumulation of triglycerides (TGs) in that tissue. Here we demonstrate that the cellular TG synthesis in HSL-deficient WAT is markedly reduced due to downregulation of the enzymatic activities of glycerophosphate acyltransferase, dihydroxyacetonphosphate acyltransferase, lysophosphatidate acyltransferase, and diacylglycerol acyltransferase. Fatty acid de novo synthesis is also decreased due to reduced cellular glucose uptake, reduced glucose incorporation into adipose tissue lipids, and reduced activities of acetyl:CoA carboxylase and fatty acid synthase. Finally, the activities of phosphoenolpyruvate carboxykinase (PEPCK), acyl:CoA synthetase (ACS), and glucose 6-phosphate dehydrogenase, the enzymes that provide glycerol-3-phosphate, acyl-CoA, and NADPH for TG synthesis, respectively, are decreased in HSL-ko mice. The reduced expression of the peroxisome proliferator-activated receptor gamma (PPAR gamma) target genes PEPCK, ACS, and aP2, as well as reduced mRNA levels of PPAR gamma itself, suggest the involvement of this transcription factor in the downregulation of lipogenesis. Taken together, these results establish that in the absence of HSL, the reduced NEFA production is counteracted by a drastic reduction of NEFA reesterification that provides sufficient quantities of NEFA for release into the circulation. These metabolic adaptations result in decreased fat mass in HSL-ko mice.

Acyltransferases↗
PubMed1999

Effects of NTE-122, an acyl-CoA:cholesterol acyltransferase inhibitor, on cholesterol esterification and lipid secretion from CaCo-2 cells, and cholesterol absorption in rats.

The effect of NTE-122 (trans-1,4-bis[[1-cyclohexyl-3-(4-dimethylamino phenyl)ureido]methyl]cyclohexane), an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on cholesterol absorption was investigated. NTE-122 inhibited whole-cell ACAT activity in CaCo-2 cells, a human intestinal cell line, with an IC50 value of 4.7 nM. In CaCo-2 cells cultured on a membrane filter, NTE-122 pronouncedly inhibited the basolateral secretion of newly synthesized cholesteryl esters, and significantly reduced the basolateral secretion of newly synthesized triglycerides without influencing the cellular triglyceride synthesis. Furthermore, NTE-122 (1 mg/kg, p.o.) inhibited [14C]cholesterol absorption in rats. These results suggest that NTE-122 is capable of exhibiting anti-hyperlipidemic effects by reducing the absorption of dietary cholesterol.

Aniline Compounds↗
PubMed2005

Esterification of Escherichia coli tRNAs with D-histidine and D-lysine by aminoacyl-tRNA synthetases.

It is generally believed that only L-amino acids are acceptable in protein synthesis, though some D-amino acids, including D-tyrosine, D-aspartate, and D-tryptophan are known to be bound enzymatically to tRNAs. In this report, we newly show that D-histidine and D-lysine are also able to be the substrates of respective Escherichia coli aminoacyl-tRNA synthetases.

Amino Acyl-tRNA Synthetases↗
PubMed1985

Cholesterol esterification in human secretory endometrium and in endometrial cancer tissue. Demonstration of microsomal acyl-CoA-cholesterol acyl-transferase (ACAT) activity.

Human secretory endometrium and endometrial cancer tissue both contain acyl-CoA:cholesterol-acyltransferase (ACAT). The optimal assay conditions for measuring ACAT activity in microsomes prepared from these tissues were determined. The activity in normal secretory endometrium was 15.3 +/- 1.27 pmol cholesteryl ester formed per mg protein-1 per min-1, whereas 3 out of 4 endometrial cancers had 3-7-fold higher ACAT activity.

Adult↗
PubMed1982

Effect of esterification and side-chain alkylation on alteration of translocation characteristics of methamidophos.

1. The phloem mobility and systemic activity of methamidophos (I); propanedioic acid 1-phosphoramidothionic acid O,S-dimethyl ester, 2-methyl, 3-0monoethyl ester (II); propanedioic acid, 1-phosphoramidothionic acid O,S-dimethyl ester, 2,2-dimethyl, 3-monoethyl ester (III); and butenoic acid, 1-monoethyl ester, 2,3,-E & Z, 3-phosphoramidothionic acid O,S-dimethyl ester (IV) were investigated in soybeans (Glycine max L.) with a bioassay using cabbage looper (Tricoplusia ni Hüber) larvae to determine the impact of side-chain alkylation on the translocation of propanedioic acid 1-phosphoramidothionic acid O,S-dimethyl ester 3-monoethyl ester (V). 2. The ethyl ester of ethanedioic acid, 1-phosphoramidothionic acid OS,-dimethyl ester 2-monoethyl ester (VI) was compared with a bukly ester analogue, the 2-(methyl)butyl ester (VII). 3. Monoethylation of the alpha-carbon of II resulted in enhanced insecticidal and systemic activity, which was interpreted as a steric hindrance to fatty acid oxidation of the propanedioic moiety of III, but not of II and V. 4. Compound IV was an effective insecticide by topical and feeding response, but was not a systemic. 5. A large bulky ester (VII) blocked deesterification and the systemic insecticidal response was lost when compared with VI. 6. This study suggests that the utilization of the malonate semialdehyde-pathway enzymes found in plants but not in insects may be fruitful in the molecular design of new insecticides.

Alkylation↗
PubMed1987

Effect of exogenous long-chain fatty acids on lipid biosynthesis in dispersed ruminant mammary gland epithelial cells: esterification of long-chain exogenous fatty acids.

Dispersed epithelial cells from lactating bovine and goat mammary glands incorporated acetate into all fatty acids (C4 to C16) that were incorporated into mainly triacylglycerols. The cells secreted free fatty acids only into the incubation medium, and this secretion was dependent on the concentration of albumin and the type and amount of exogenous fatty acid added to the medium. Addition of palmitic acid to the incubation medium stimulated synthesis and incorporation of fatty acids synthesized de novo into triacylglycerols, whereas stearic and linoleic acid were inhibitory.

Acetates↗
PubMed1999

Esterification makes retinol more labile to photolysis.

Because retinyl palmitate was reported to be more stable to oxidation than retinol, we wondered if retinyl palmitate was also more resistant to photolysis as compared to free alcohol. We investigated the resistance of ethanolic solutions of retinol, retinyl palmitate, or both to air oxidation and (or) photolysis using fluorescent light. The initial concentrations were all-trans-retinol, 14 mumol/L, and all-trans-retinyl palmitate, 14 mumol/L. The concentrations of retinol and retinyl palmitate were determined by HPLC and are expressed as a percentage of their original concentrations. After 4 h of exposure to an 18 W fluorescent lamp at 15 cm from the solution, the means (SD) of the surviving analytes were 64% (3%) for retinol and 5% (2%) for retinyl palmitate in a solution containing both retinol and retinyl palmitate. Taking account of the cis isomer arising from retinyl palmitate, 29% (3%) of the retinyl palmitate survived after 4 h of photolysis. Degradation of retinyl palmitate might occur after the conversion of trans isomer to cis isomer during photolysis, however, trans isomer could be degraded with a lesser extent of isomerization. After 4 h of bubbling air through the solution in the dark, 49% (6%) of retinol and 69% (4%) of retinyl palmitate survived. Exposing retinol or retinyl palmitate separately to air oxidation, bubbling air through the solution, or photolysis, exposing them to light, we found that retinyl palmitate could retard the air oxidation of retinol (p < 0.001), but it had no effect on the light-induced degradation of retinol. We also studied the effect of the addition of approximately 1,560 mumol/L alpha-tocopherol, approximately 190 mumol/L beta-carotene and approximately 2,000 mumol/L ascorbic acid as antioxidants. In the presence of 156 mumol/L alpha-tocopherol, 87% (1%) of the retinol and 91% (4%) of the retinyl palmitate remained after air oxidation. Although the photolysis of retinol and retinyl palmitate was also inhibited by 190 mumol/L beta-carotene, alpha-tocopherol and ascorbic acid did not exert inhibiting effects. We conclude that retinyl palmitate is physico-chemically more labile to photolysis but is more resistant to air oxidation than retinol.

Air↗