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At least 181 records · Page 10Linked to original sources
PubMed2004

Determination of the kinetic properties of platycodin D for the inhibition of pancreatic lipase using a 1,2-diglyceride-based colorimetric assay.

A 1, 2-diglyceride-based multi-step colorimetric assay to measure the pancreatic lipase activity was applied for the determination of the kinetic profiles of the lipase inhibition with a slight modification and the validity verification. With this assay method, our study revealed that platycodin D, one of major constituents of Platycodi Radix, inhibits the pancreatic lipase activity in a competitive type, with the value of Kl being 0.18 +/- 0.02 mM. In addition, PD has affected the values of Km,app and Kcat/Km in a dose- dependent manner. The results shed a meaningful light on how PD mediates lipid metabolism in the intestinal tracts. On the other hand, since the revised assay is sensitive, rapid, and does not affect the accuracy to the kinetic properties, it is applicable not only to evaluation of the kinetic properties of the pancreatic lipase, but also to high-throughput screening of pancreatic lipase activity.

Anti-Obesity Agents↗
PubMed1982

Diglyceride kinase from Escherichia coli. Modulation of enzyme activity by glycosphingolipids.

Diglyceride kinase was purified from membranes of Escherichia coli K-12 using organic solvents. The enzyme apoprotein depended on lipids, such as cardiolipin (diphosphatidylglycerol), phosphatidylcholine or 1-monooleoylglycerol, for activity with 1,2-dipalmitoylglycerol. Mixed brain cerebrosides and gangliosides as well as defined ganglioside fractions and synthetic lactocerebroside were devoid of lipid cofactor activity. However, all these glycosphingolipids were strong inhibitors of activation by phosphatidylcholine. When cardiolipin was used as lipid activator with the detergent, Triton X-100, as solubilizing agent, the addition of mixed or purified gangliosides first (at about 0.4 mM) resulted in additional activation, but higher ganglioside concentrations were strongly inhibitory. Both effects were absolutely dependent on the presence of lipid-bound sialic acid and were not given by cerebrosides, by free sialic acid or by sialyl-lactose. The stimulating and inhibitory effects of glycosphingolipids could also be demonstrated when 1-monooleoylglycerol was used as substrate, lipid activator and solubilizing agent at the same time. The modulation of kinase activity by glycosphingolipids is discussed at the level of lipid/protein interactions.

Cardiolipins↗
PubMed1984

Absence of diglyceride kinase activity in the photoreceptor cells of Drosophila mutants.

Diglyceride kinase (DG) activity was found to be almost absent in the photoreceptor cells of Drosophila vision mutants, norpA (no receptor potential A). Other enzymes related to the phosphatidic acid (PA) metabolism, such as monoacyl-glycerophosphate acyltransferase and PA phosphatase, were normal in the mutant. The deficiency in PA content in the retinular cells of norpA, demonstrated by 32P incorporation in vivo is, therefore, due to abnormal reduction in DG kinase activity. The DG kinase was found to be localized in the retinular cell by assaying its activity in the mutants rdgA (receptor cells degenerated) and sine oculis (compound eyes absent).

Animals↗
PubMed1996

Cloning of the Pseudomonas aeruginosa gene encoding CDP-diglyceride synthetase.

The CDP-diglyceride synthetase (CDS)-encoding gene (cds) from Pseudomonas aeruginosa PAO1 was cloned and sequenced. The gene possessed an open reading frame of 813 bp capable of encoding a putative polypeptide of 271 amino acids (aa) (28 699 Da). The deduced aa sequence of CDS revealed a 67% similarity (45% identity) to Escherichia coli CDS.

Amino Acid Sequence↗
PubMed1991

High-performance liquid chromatographic analysis of 3'-azido-3'-deoxythymidine monophosphate diglyceride, an anti-HIV glycerophospholipid.

A reversed-phase chromatographic method is described for the analysis of an experimental anti-AIDS drug 3'-azido-3'-deoxythymidine monophosphate diglyceride (AZT-MP-DG) [J.M. Steim et al., Biochem. Biophys. Res. Commun. 171, 458-464 (1990)] [1], a phosphatidic acid derivative of AZT. Analytical conditions were based upon conventional separations of glycerophospholipid species. Where AZT-MP-DG was monitored by UV absorption, there were two wavelength maxima. The response was linear in the concentration range used in this study. The peak was characterized by absorbance ratios with a rapid scanning UV detector.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Effect of the diglyceride lipase inhibitor, RG80267, on epithelial chloride secretion induced by various agents.

We previously reported that a diglyceride lipase inhibitor, RG80267, inhibits chloride secretion stimulated by adenosine agonists, stimuli whose effects appear unrelated to cAMP, cGMP or cytosolic calcium. Here, the effect of RG80267 on Cl- secretory responses to agents which do utilize these messengers was examined. RG80267 inhibited responses to vasoactive intestinal polypeptide, forskolin (cAMP-dependent) and E. coli heat stable enterotoxin (cGMP-dependent), but not to prostaglandin E1 or cholera toxin (cAMP-dependent). RG80267 enhanced responses to histamine (calcium-dependent). The inhibitory effect of RG80267 was not due to inhibition of cAMP accumulation. Arachidonic acid release may participate in chloride secretion. Vasoactive intestinal polypeptide, but not prostaglandin E1, released radiolabel from cells preloaded with [3H]arachidonic acid. There may thus be differences between mechanisms of various cyclic nucleotide-dependent chloride secretory responses. Arachidonic acid release may modulate the extent of secretion elicited by some secretagogues.

Alprostadil↗
PubMed2006

Chemoenzymatic synthesis and antimicrobial activity evaluation of monoglucosyl diglycerides.

Monoglucosyl diglycerides with medium-long length fatty acid acyl chains were prepared and examined for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The study of their in vitro antimicrobial activity confirms the significant activity of some monoglucosyl diacylglycerol analogues and establishes for the glucose series that the 1,2-disubstitution and the octanoyl chain are the proper structural features for the maximum activity.

Anti-Bacterial Agents↗
PubMed1966

Bacterial glycolipids. Glycosyl diglycerides in gram-positive bacteria.

1. The lipids of ten Gram-positive bacteria have been isolated and the presence in each of a glycosyl diglyceride was established. 2. The glycolipid fractions were isolated and deacylated to give water-soluble glycosides which were purified by paper chromatography. Partial structures for the glycosides have been deduced from chemical and enzymic studies. 3. Nine of the glycosides were disaccharides glycosidically linked to the 1-position of glycerol: the remaining glycoside contained a trisaccharide similarly linked to glycerol.

Bacillus subtilis↗
PubMed1989

In-vitro evaluation of filaricidal activity of GABA and 1,3-dipalmitoyl-2-(4-aminobutyryl)glycerol HCl: a diglyceride prodrug.

A diglyceride ester of gamma-aminobutyric acid (GABA) has been synthesized and its filaricidal activity compared with GABA, and progabide in-vitro, on infective larvae and microfilariae of Molinema dessetae, a rodent filaria. GABA induced paralysis in infective larvae but was inactive on microfilariae. There were interactions between the culture medium and GABA. The ester drug at 0.1 mmol L-1 (1,3-dipalmitoyl-2-(4-aminobutyryl)glycerol HCl) was as active as progabide on infective larvae and hundredfold more potent than GABA. Its microfilaricidal activity at 1 mmol L-1 was lower than that progabide at 0.1 mmol L-1 but a delayed effect was observed. The data confirm filariae sensitivity to GABA derivatives.

Animals↗
PubMed1976

Studies on the formation by rat brain preparations of CDP-diglyceride from CTP and phosphatidic acids of varying fatty acid compositions.

The enzyme, CTP:phosphatidate cytidylyltransferase (EC2.7.7.41) which catalyses formation of CDP-diglyceride from CTP and phosphatidic acid has been studied in rat brain preparations and other tissues. Improvement, as judged by the higher tissue activities obtained, in the assay method for this enzyme was achieved through use of phosphatidic acids sonicated in buffer-detergent solution saturated with ether and containing bovine serum albumin and use of short incubation times which essentially provided a measure of initial rates. The enzyme of rat brain microsomes yielded with 1,2-dioleolphosphatidic acid as substrate a pH optimum of 6.8 with maleate buffer and optimal concentrations of 60mM for MG2+, 6MM for CTP and 250 mug per 0.8 ml for phosphatidic acid. Enzyme activity was mainly located in the 90,000 X g fraction (microsomal) with small but significant activity in the 12,000 X g fraction. Comparison of activities (nanomoles CTP incorporated per milligram protein per minute) amongst tissues showed the following order: brain, 1.87; liver, 1.32; lung, 1.19; small intestine, 1.00; kidney, 0.69; heart, 0.41; diaphragm, 0.07; skeletal muscle, 0.02. Examination of the effect of varying the fatty acid composition in the phosphatidic acids added exogenously gave the following order (activities in parentheses); 1-stearoyl-2-oleoyl- (5.58), 1-oleoyl-2-stearoyl- (5.37), 1,2-dioleoyl- (4.49) 1-palmitoyl-2-oleoyl-(3.85), 1-stearoyl-2-arachidonoyl-(3.31), 1-arachidonoyl-2-stearoyl-(3.16), 1,2-diarachidonoyl-(0.72), 1,2-dicaproyl-(0.67), 1,2-dipalmitoyl-(0.67) and 1,2-distearoyl-(0.18). The single bis- and lysophosphatidic acids tested were inactive as substrates. Apart from a possible preference for one or more unsaturated fatty acids the transferase enzyme showed no selectivity in respect to the fatty acid distribution of phosphatidic acids.

Animals↗
PubMedDate not supplied

Effect of carotenoids and monogalactosyl diglyceride on bacteriochlorophyll c aggregates in aqueous buffer: implications for the self-assembly of chlorosomes.

Aggregation of bacteriochlorophyll (BChl) c from chlorosomes, the main light-harvesting complex of green bacteria, has been studied in aqueous buffer. Unlike other chlorophyll-like molecules, BChl c is rather soluble in aqueous buffer, forming dimers. When BChl c is mixed with carotenoids (Car), the BChl c Qy transition is further redshifted, in respect to that of monomers and dimers. The results suggest that Car are incorporated in the aggregates and induce further aggregation of BChl c. The redshift of the BChl c Qy band is proportional to the Car concentration. In contrast, the mixture of bacteriochlorophyllide (BChlide) c, which lacks the nonpolar esterifying alcohol, does not form aggregates with Car in aqueous buffer or nonpolar solvents. Instead, the position of the BChlide c Qy transition remains unshifted in respect to that of the monomeric molecule, and Car precipitates with the course of time in aqueous buffer. Similar effects on both BChl c and BChlide c are also observed when monogalactosyl diglyceride (MGDG), which forms the monolayer envelope of chlorosomes, is used instead of (or together with) Car. The results show that the hydrophobic interactions of the BChl c esterifying alcohols with themselves and the nonpolar carbon skeleton of Car, or the fatty acid tails of MGDG, are essential driving forces for BChl aggregation in chlorosomes.

Bacterial Proteins↗
PubMed1999

Incorporation of an (125)I-labeled hexa-iodinated diglyceride analog into low-density lipoprotein and high specific uptake by cells of cervical carcinoma cell lines.

The feasibility of using low-density lipoprotein (LDL) to deliver cytotoxic drugs to tumor cells has been explored since the 1980s, when cells of a number of cancer cell lines were found to have higher LDL receptor activity than normal cells. Such differential uptake between tumor and normal cells may provide a unique opportunity to use LDL as a tumor-specific carrier of radiopharmaceuticals for the clinical management of cancer. In this study, an (125)I-labeled hexa-iodinated diglyceride analog, 1, 3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), was synthesized and incorporated into LDL using a fusion technique. It was found that approximately 500 [(125)I] DPIP molecules were incorporated into each LDL particle. Cells of three human cervical tumor cell lines, HeLa, SiHa and C-33A, were used to examine the cellular uptake of the [(125)I]DPIP-LDL conjugate. It was shown that the [(125)I]DPIP-LDL conjugate was specifically bound to and taken up by cervical tumor cells through an LDL receptor-mediated endocytosis pathway. The results suggest that LDL may be a selective carrier for delivering hydrophobic radiopharmaceuticals to cancer cells and particularly for the diagnosis of cervical tumors.

Binding Sites↗
PubMed1985

Purification and properties of the membrane-bound CDP-diglyceride synthetase from Escherichia coli.

The enzyme CDP-diglyceride synthetase (CTP: phosphatidate cytidylyltransferase; EC 2.7.7.41) has been purified to 90% homogeneity from Escherichia coli cells that overproduce the enzyme 50-fold through the use of recombinant DNA technology. The purification required the use of different detergents at each step, illustrating the refractory hydrophobic nature of this protein. Apparent physical effects of EDTA on the enzyme were also utilized in the purification. The enzyme has an apparent minimum subunit mass of 27,000 daltons, as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The amino acid composition of the protein was determined, and it correlates well with the theoretical protein product of the cds gene, the sequence of which is reported in the accompanying paper (Icho, T., Sparrow, C. P., and Raetz, C. R. H. (1985) J. Biol. Chem. 260, 12078-12083). The pure enzyme displays surface dilution kinetics when assayed in the presence of Triton X-100. As previously suggested on the basis of studies using partially purified preparations, the enzyme mechanism is sequential, and computer-calculated kinetic constants are reported herein. The substrate specificity of the enzyme is also investigated. This is the first time this enzyme has been purified to homogeneity from any source, despite the fact that it is essential for phospholipid biosynthesis in all organisms.

Amino Acids↗
PubMed1973

Diglyceride kinase in human platelets.

Human platelets contain diglyceride kinase, an enzyme that catalyzes the phosphorylation of diacylglycerol by adenosine 5'-triphosphate to yield phosphatidic acid. The majority of the platelet enzyme is particulate-bound, and membrane fractions of platelet homogenates have a higher specific activity than granule fractions. Both deoxycholate and magnesium are necessary for optimal enzyme activity. The K(m) of the enzyme for adenosine 5'-triphosphate is 1.3 mm, and the apparent K(m) for diacylglycerol is 0.4 mm. The pH optimum is 6.6-6.8 in imidazole-HCl or maleate-NaOH buffer. The enzyme activity of platelets from normal subjects was similar to the activity from patients with renal and hepatic failure.

Adenosine Triphosphate↗
PubMed1976

Triglyceride, diglyceride, monoglyceride, and cholesterol ester hydrolases in chicken adipose tissue activated by adenosine 3':5'-Monophosphate-dependent protein kinase. Chromatographic resolution and immunochemical differentiation from lipoprotein lipase.

Hormone-sensitive lipase and cholesterol ester hydrolase of chicken adipose tissue were markedly activated by adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase (on the average, 235 to 275%; occasionally as much as 1000%). Diglyceride and monoglyceride hydrolases were also activated, but to a lesser extent (60 to 87%). The activation of all four hydrolases was inhibited by protein kinase inhibitor and reversed by the addition of exogenous protein kinase. Following activation by cAMP-dependent protein kinase, all four hydrolases were deactivated in a Mg2+-dependent reaction and then reactivated to or near initial levels on incubation with cAMP and Mg2+-ATP. The reversible deactivation is assumed to reflect activity of one or more protein phosphatases. The maximum activation obtainable for the four hydrolases decreased when the tissue had been previously exposed to glucagon, indicating that the glucagon-induced activation was probably similar to or identical with the activation demonstrated in cell-free preparations. The pH optima for the four hydrolase activities were similar (7.13 to 7.38). Although the absolute activities and relative degrees of kinase activation differed according to the particular emulsified substrates used, the results do not rule out the possibility that all four hydrolase activities are referable to a single hormone-sensitive hydrolase. Hormone-sensitive acyl hydrolases were separated from lipoprotein lipase by heparin-Sepharose affinity chromatography. Lipoprotein lipase was active against triolein, diolein, and monoolein, but not cholesterol oleate. Incubation of lipoprotein lipase with exogenous protein kinase, cAMP, and Mg2+ATP had no effect on any of the three hydrolase activities. Lipoprotein lipase was further purified to homogeneity and used to prepare antiserum in rabbits. The immunoglobin G fraction from these antisera completely inhibited lipoprotein lipase eluted from heparin-Sepharose columns. However, the hormone-sensitive hydrolase activities (not retained on heparin-Sepharose affinity chromatography) were not inhibited by anti-lipoprotein lipase immunoglobin G, and anti-lopoprotein lipase immunoglobin G did not affect the activation process in crude fractions. Thus, hormone-sensitive lipase and lipoprotein lipase, functionally distinct enzymes, have been physically resolved and immunochemically distinguished. Apparently lipoprotein lipase activity is not regulated, at least directly, by cAMP-dependent protein kinase.

Adenosine Triphosphate↗
PubMed1996

Low nanogram range quantitation of diglycerides and ceramide by high-performance liquid chromatography.

A method for ceramide (CER) and diradylglycerol (DG) determination after normal-phase HPLC separation was developed. The free oxydril group of ceramide and diradylglycerol is coupled to the carboxylic group of the fluorescent label (+)-6-methoxy-alpha-methyl-2 naphthaleneacetic acid (NAP), using as catalytic agents 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide. The use of NAP-free acid instead of the halide-activated form ensures higher stability of the reagent, lower reaction temperatures, and improved yield and reproducibility. The yield of the reaction is greater than 90% after a period of 3 h at the temperature of -20 degrees C. Over 85% of the starting material is recovered at the end of HPLC separation. The lower detection limit is below 5 ng for CER and 150 ng for DG. Under the conditions employed in the assay, no significant hydrolysis of triglycerides, sphingolipids, or phospholipids occurs and the esterification reaction is not affected by components of crude lipid extracts. Since separation and/or purification steps are not required, cellular levels of CER and DG can be easily and rapidly measured.

Cell Line↗