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Biomedical subjects

M Waite

Publications and source records attributed to M Waite.

At least 37 records · Page 2Linked to original sources
PubMed1993

von Willebrand factor and endothelial damage in essential hypertension.

The relationship between von Willebrand factor antigen (vWFAg, a specific endothelial cell product) and hypertension was examined. Circulating vWFAg levels were measured in serum from patients attending a hypertension clinic and in normotensive controls. The vWFAg was higher in those patients with uncontrolled hypertension at 131 +/- 34 IU/dl than in controls (90 +/- 30 IU/dl) and in those whose hypertension was controlled 104 +/- 29 IU/dl (P < 0.001). Levels of vWFAg correlated with both SBP (r = 0.42, P < 0.0002) and DBP (r = 0.25, P < 0.05), but serum from neither group of patients was more cytotoxic to cultured endothelial cells in vitro than was serum from controls. Neither symptoms of cardiovascular or peripheral vascular disease or two of its risk factors (hypercholesterolaemia or smoking, alone or in combination) appeared to further increase vWFAg in patients with uncontrolled hypertension. However, vascular disease and the same risk factors did increase vWFAg to 133 +/- 36 IU/dl in those patients with controlled hypertension (P < 0.001). These data indicate a relationship between vWFAg and hypertension and suggest that endothelial damage may indeed be important in the vascular complications of hypertension.

Adult↗
PubMed1992

Action of lysosomal phospholipase A1 on bis(monoacylglycerol)phosphate.

Bis(monoacylglycerol)phosphate (BMP) in macrophages is known to rapidly turn over its acyl moiety(s) located at primary positions of the glycerols, yet the glycerols and phosphate remain stable within the BMP molecule. Here we examine whether the phospholipase A1 isolated from rat-liver lysosomes is capable of deacylating BMP. By comparison with the precursor of BMP, phosphatidylglycerol, BMP is a very poor substrate for the phospholipase A1. We conclude, therefore, that a direct deacylation of the acyl groups at the primary alcohol level of the glycerol probably does not occur, but postulate that transacylations may occur to account for the removal of the acyl moiety.

Animals↗
PubMed1992

Role of apolipoprotein E in hepatic lipase catalyzed hydrolysis of phospholipid in high-density lipoproteins.

We reported earlier that hepatic lipase (HL)-catalyzed hydrolysis of phospholipid monolayers is activated by apolipoprotein (apo) E [Thuren et al. (1991b) J. Biol. Chem. 266, 4853-4861]. On the basis of these studies, it was postulated that apoE-rich high-density lipoproteins (HDL) were preferred substrates for HL. In the present study, we tested this hypothesis, as well as further characterizing the activation of HL hydrolysis of phospholipid by apoE. The apoE-rich HDL, referred to as HDL-I, were isolated by heparin-Sepharose chromatography, and the phospholipid hydrolysis by HL was compared to an apoE-poor HDL, designated HDL-II. The hydrolysis of HDL-I phosphatidylcholine was approximately 3-fold higher than HDL-II, supporting the hypothesis that HL preferably hydrolyzes the phospholipids in apoE-rich HDL. In order to gain additional insight into the nature of the activation, we used phospholipid monolayers as model systems. Comparison of the ability of the two thrombolytic fragments of apoE (22 kDa, residues 1-191; 12 kDa, residues 192-299) revealed that only the 12-kDa fragment was capable of activating the hydrolysis of phospholipid by HL (1.75-fold). However, activation was less than with the intact protein (2.8-fold for apoE3), suggesting that the intact protein was required for full activation. The fact that the 12-kDa fragment, which represents a major lipid region of the protein, did activate HL suggests that activation occurs at the lipid-water interface.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1992

Phosphatidylinositol hydrolysis by phospholipase A2 and C activities in human peripheral blood neutrophils.

We describe here and partially characterize a Ca(2+)-independent phospholipase A2 that acts on phosphatidylinositol in normal human peripheral blood neutrophils. Neutrophils incubated with myo-[3H]inositol to form [3H]phosphatidylinositol and then stimulated with the calcium ionophore A23187 produced [3H]lysophosphatidylinositol. This deacylation was further characterized in cell sonicates by the specific release of [3H]arachidonic acid from exogenous [1-14C]stearoyl-2-[3H]arachidonyl-phosphatidylinositol. This phospholipase A2 is Ca2+ independent, retaining full activity in the presence of 10 mM EDTA, and is optimally active at alkaline pH (pH 9). A phosphatidylinositol-hydrolyzing phospholipase C activity was characterized by the production of [3H]-/[14C]-diglycerides. This phospholipase C activity is dependent on the presence of exogenous Ca2+ and is optimally active at neutral pH (pH 7.5). The lipoxygenase/cyclooxygenase inhibitors eicosatetraenoic acid and nordihydroguaiaretic acid and the calmodulin antagonist trifluoperazine were the only compounds tested that showed significant inhibition of phospholipase A2 activity. However, none of these phosphatidylinositol-hydrolyzing phospholipase A2 inhibitory compounds resulted in the accumulation of any radiolabeled diglyceride, monoglyceride, or phosphatidic acid intermediates. Following subcellular fractionation on sucrose density gradients, it was found that the plasma membrane-enriched fractions contained the highest specific activity for phospholipase A2; however, the cytosolic fraction contained a large part of the total phospholipase A2 activity. Furthermore, when neutrophils were first exposed to several agents, including lipopolysaccharide, phorbol myristate acetate, or N-formyl-methionyl-leucyl- phenylalanine, and then subfractionated, there was a significant translocation of the enzyme activity from the cytosolic fraction to the membrane-enriched fractions. These data suggest that this Ca(2+)-independent, phosphatidylinositol-hydrolyzing phospholipase A2 may play an important role in early cell activation, providing free arachidonic acid for subsequent metabolism into biologically active eicosanoids.

Arachidonic Acid↗
PubMed1991

Activation of hepatic lipase catalyzed phosphatidylcholine hydrolysis by apolipoprotein E.

The effect of apolipoproteins A-I, A-II, C-II, C-III and E on the hydrolysis of phosphatidylcholine and triacylglycerol by hepatic lipase was studied. Hepatic lipase catalyzed phospholipid hydrolysis was 1.8-fold activated by apolipoprotein E while the other apolipoproteins did not affect the hydrolysis by this enzyme. Triacylglycerol hydrolysis by hepatic lipase was 1.5-fold activated by apolipoprotein E while the other apolipoproteins inhibited hepatic lipase. These results suggest that lipoproteins containing apolipoprotein E may be preferred substrates for hepatic lipase.

Animals↗
PubMed1991

Glycerol reorientation during the conversion of phosphatidylglycerol to bis(monoacylglycerol)phosphate in macrophage-like RAW 264.7 cells.

Bis(monoacylglycero)phosphate (BMP) has the unique stereoconfiguration of 3-acyl-sn-glycero-1-phosphoryl-1'-sn-[3'-acylglycerol] (Brotherus, J., Renkonen, O., Herrmann, J., and Fischer, W. (1974) Chem. Phys. Lipids 13, 178-182) which differs from other known mammalian phospholipids that have the sn-glycero-3-phosphoryl configuration. This stereochemistry may contribute to its physiologic function. Here we describe studies using the macrophage-like cell line RAW 264.7 designed to determined how this unique stereoconfiguration occurs. These studies show that the stereoconfiguration of BMP produced from exogenous phosphatidylglycerol (PG) by RAW 264.7 cells has the expected stereoconfiguration of 3-acyl-sn-glycero-1-phosphoryl-1'-sn-[3'-acylglycerol]. Experiments using diacyl-sn-[2-3H]glycero-3-phosphoryl-sn-1'-[2-3H]glycerol demonstrate that this unique stereoconfiguration is not produced due to an oxidation/reduction mechanism involving the sn-2-glycerol carbon. When dioleoyl-sn-[1-14C]glycero-3-phosphoryl-rac-glycerol was converted to 14C-labeled BMP, the 14C label was found esterified to the phosphate moiety. These results suggest that a stereospecific enzyme is capable of reorienting the radiolabeled glycerol backbone of this PG substrate, effectively changing the stereochemistry of the lipid. We also show that this enzyme is stereoselective with regard to the base glycerol moiety of the substrate PG used. Finally, we propose a new pathway for the synthesis of BMP from PG.

Animals↗
PubMed1991

Hepatic lipase hydrolysis of lipid monolayers. Regulation by apolipoproteins.

A monolayer technique was used to study the substrate specificity of hepatic lipase (HL) and the effect of surface pressure and apolipoproteins on hydrolysis of lipid monolayers by this enzyme. HL hydrolyzed readily phosphatidylethanolamine monolayers. Pure trioctanoylglycerol was found to be a poor substrate but when progressively diluted with nonhydrolyzable 1,2-didodecanoylphosphatidylcholine hydrolysis of triacylglycerol by HL reached maximum at a molar ratio of 1:1 triacylglycerol to phosphatidylcholine. The activation of triacylglycerol hydrolysis was not due to altered penetration of HL. The surface pressure optimum of HL for the hydrolysis of phosphatidylethanolamine monolayers was broad between 12.5 and 25 mN/m. When apolipoprotein E was injected beneath the monolayer of phosphatidylethanolamine prior to enzyme addition, a 3-fold activation of HL was observed at surface pressures equal to or below 15 mN/m. Below surface pressures of 20 mN/m apolipoprotein E did not affect the penetration of HL into the lipid-water interface. Apolipoprotein E slightly activated the hydrolysis of triacylglycerol by HL at 10 mN/m. At a high surface pressure of 25 mN/m all apolipoproteins tested (apolipoproteins A-I, A-II, C-I, C-II, C-III, and E) inhibited the penetration into and HL activity on phosphatidylethanolamine At 18.5 mN/m all apolipoproteins except apolipoprotein E inhibited the hydrolysis of triacylglycerol in the triacylglycerol:phosphatidylcholine mixed film. Based on these results we present a hypothesis that phospholipid present in apolipoprotein E-rich high density lipoprotein-1 and triacylglycerol in intermediate density lipoprotein would be preferred substrates for HL.

Animals↗
PubMed1991

Hydrolysis of neutral lipid substrates by rat hepatic lipase.

Rat hepatic lipase, an enzyme whose involvement in the catabolism of lipoproteins remains poorly defined, has both neutral lipid and phospholipid hydrolyzing activity. We determined the substrate specificity of hepatic lipase for 1-oleoyl-sn-glycerol, 1,2-dioleoyl-sn-glycerol, and 1,3-dioleoyl-sn-glycerol in the Triton X-100 mixed micellar state, and compared these results to those obtained previously in our laboratory for the phospholipid substrates phosphatidic acid (PA), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). Vmax values were determined by diluting the substrate concentration in the surface of the micelle by Triton X-100. The Vmax values obtained were 144 mumol/min/mg for 1-oleoyl-sn-glycerol, 163 mumol/min/mg for 1,2-dioleoyl-sn-glycerol, and 145 mumol/min/mg for 1,3-dioleoyl-sn-glycerol. These values were higher than those obtained earlier for phospholipids which were 67 mumol/min/mg for PA, 50 mumol/min/mg for PE and 4 mumol/min/mg for PC. In addition, the mole fraction of lipid substrate at half maximal velocity (K) in the surface dilution plot was lower for the neutral lipid substrates as compared to those obtained for the phospholipid substrates. When the hydrolysis of 1,3-dioleoyl-sn-glycerol mixed micelles was studied as a function of time, cleavage at the sn-1 and sn-3 positions occurred at the same rate, suggesting that hepatic lipase is not stereoselective with respect to 1,3-diacyl-sn-glycerol substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Anticardiolipin antibodies in leptospirosis.

The clinical course and serology of 16 cases of leptospirosis in an area with an unusually high endemic infection rate were studied to gain further insight into the pathology of the secondary immune phase that is typical of the disease. IgG anticardiolipin antibody concentrations were measured by immunoassay and found to be increased in eight serologically confirmed cases with severe complicated disease, compared with eight patients with relatively uncomplicated leptospirosis who had IgG anticardiolipin concentrations within the control reference range. This previously unreported association suggests that leptospira may induce vascular endothelial injury in severe cases and expose crypt antigens or induce conformational change of cell surface phospholipids. Leptospirosis may provide a model for an infective origin of some cases of the antiphospholipid syndrome.

Autoantibodies↗
PubMed1990

Metabolism of phosphatidylglycerol and bis(monoacylglycero)-phosphate in macrophage subcellular fractions.

Bis(monoacylglycero)phosphate (BMP) is synthesized from exogenous phosphatidylglycerol (PG) by macrophages (Cochran, F. R., Roddick, V. L., Connor, J. R., Thornburg, J. T., and Waite, M. (1987) J. Immunol. 138, 1877-1883). Previous work from our laboratory showed that arachidonic acid in BMP was released by the macrophages upon challenge of the cells with PMA (Cochran, F. R., Connor, J. R., Roddick, V. L., and Waite, M. (1985) Biochem. Biophys. Res. Commun. 130, 800-806). Here we extend those studies using a model cultured cell line of macrophages, RAW 264.7. When PG labeled with 32P- and [3H]glycerol in both moieties was added to the culture medium, 32P/[3H]BMP was synthesized in a time-dependent manner. Fractionation of cell homogenates on a discontinuous sucrose gradient in which the light membranes were floated from dense sucrose showed an enrichment of [3H]BMP in light membrane fractions. The precursor [3H]PG was also found in the light fractions but, relative to the [3H]BMP, was more abundant in the denser membrane fractions. The appearance of [3H]PG and [3H]BMP in the light membrane fraction was time-dependent which suggested that the initial uptake and metabolism of [3H]PG was into the denser membranes. Incubation of the light membranes under conditions that are optimal for the lysosomal phospholipase A1 led to significant metabolism of [3H]PG. Both degradation of [3H]PG to water-soluble compounds and its conversion to acylphosphatidylglycerol occurred while no lyso-PG was detected. On the other hand, little BMP was found to be degraded. From these studies we postulate that in lysosomes acylphosphatidylglycerol is a precursor of BMP and that the previously reported turnover of arachidonic acid by BMP may occur via transacylation rather than hydrolysis.

Animals↗
PubMed1990

Hydrolysis of lipid mixtures by rat hepatic lipase.

The hydrolysis of phospholipid mixtures by purified rat hepatic lipase, also known as hepatic triglyceride lipase, was studied in a Triton X-100/lipid mixed micellar system. Column chromatography of the mixed micelles showed elution of Triton X-100 and binary lipid mixtures of phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine as a single peak. This indicated that the mixed micelles were homogenous and contained all components in the designated molar ratios. The molar ratio of Triton X-100 to lipid was kept constant at 4 to 1. Labeling one lipid with 3H and the other lipid with 14C enabled us to determine the hydrolysis of both components of these binary lipid mixed micelles. We found that the hydrolysis of phosphatidylcholine was activated by the inclusion of small amounts of phosphatidic acid (2.5-fold), phosphatidylethanolamine (1.5-fold) or phosphatidylserine (1.4-fold). The maximal activation of phosphatidylcholine hydrolysis was observed when 5 mol% of phosphatidylethanolamine, 7.5 mol% phosphatidic acid or 5 mol% phosphatidylserine was added to Triton X-100 mixed micelles. The hydrolysis of phosphatidic acid was activated 30%, and that of phosphatidylserine was inhibited 30% when the molar proportion of phosphatidylcholine was less than 50 mol%. The hydrolysis of phosphatidylethanolamine was slightly activated when the mol% of phosphatidylcholine was below 5. The hydrolysis of phosphatidylserine was inhibited by phosphatidylethanolamine when the mol% of the latter was 50 or less whereas phosphatidylethanolamine hydrolysis was not affected by phosphatidylserine. Under the conditions used sphingomyelin and cholesterol did not have a significant effect on the hydrolysis of the phospholipids studied. In agreement with our previous study (Kucera et al. (1988) J. Biol. Chem. 263, 1920-1928) these studies show that the phospholipid polar head group is an important factor which influences the action of hepatic lipase and that the interfacial properties of the substrate play a role in the expression of the activity of this enzyme. The molar ratios of phosphatidic acid, phosphatidylethanolamine and phosphatidylserine which activated phosphatidylcholine hydrolysis correspond closely to the molar ratios of these lipids found in the surface lipid film of lipoproteins e.g., high density lipoproteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Phospholipases, enzymes that share a substrate class.

Considerable work has gone into the study of PLs since the first suggestions of their existence nearly a century ago. This work has intensified enormously since the mid-1970s when their role in signal-coupling mechanisms and in pathophysiology was recognized. While much has been done to understand this diverse group of enzymes at the molecular and mechanistic levels, the discovery of new PLs has far outstripped our capacity to study them in sufficient detail to appreciate what makes each unique while perhaps having some common mechanisms of action and regulation. One would almost plead: No new PLs - Let us study those at hand! That is not the case in our field and the discovery of new PLs will continue. It is important, however, that an understanding be gained of these enzymes at the molecular level, how they interact with their substrates, and how regulatory factors can target the function of PLs in situ.

Amino Acid Sequence↗
PubMed1989

Studies of phospholipase and cyclooxygenase activities in herpes simplex virus type 2-transformed rat cells.

In this report we describe results showing that both arachidonic acid (20:4) release and prostaglandin (PG) synthesis in herpes simplex virus type 2 (HSV-2)-transformed tumor-derived rat fibrosarcoma (RFS) cells are inhibited by indomethacin (cyclooxygenase inhibitor). These data suggest that cyclooxygenase (prostaglandin endoperoxide synthetase, PES) and phospholipase are coupled in their regulation in RFS cells. Data obtained using a cell-free assay to measure directly cyclooxygenase specific activity in the absence of phospholipase activity indicate that constitutive cyclooxygenase activity is very low in non-transformed REF and is not induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). In contrast, after an initial degradation of constitutive enzyme, cyclooxygenase is synthesized de novo following TPA treatment of HSV-2-transformed RFS clonal cells. At least a 5-fold induction of cyclooxygenase occurs by 6 h post-treatment of HSV-2-transformed RFS clonal cells. This induction is inhibited by pretreatment of cells with cycloheximide (protein synthesis inhibitor) 1 h prior to TPA treatment. Results obtained following delayed addition of cycloheximide to cells after TPA treatment indicate that the newly synthesized cyclooxygenase has a half-life of approximately 5 min. In addition, HSV-2-transformed RFS clonal cells at low passage (less than 10) show over a 3-fold greater increase in cyclooxygenase specific activity after TPA treatment compared to that in TPA-treated high passage (greater than 20) cells, suggesting that induction of high levels of PG synthesis is transient in these cells. These data indicate that HSV-2 transformation of REF cells is associated with alteration of cyclooxygenase regulation.

Animals↗
PubMed1988

Hydrolysis of thioester analogs by rat liver phospholipase A1.

The hydrolysis of thioester containing phospholipids by rat liver plasmalemma phospholipase A1 was measured in a continuous spectrophotometric assay. In this assay thioester substrates were employed which, upon hydrolysis, liberated a free thiol which was reacted with 4,4'-dithiopyridine to yield the product 4-thiopyridone that absorbs at 324 nm. Thioester substrates, prepared by chemical synthesis, were used in phospholipid and Triton X-100 micelles for kinetic analysis carried out according to the method of Hendrickson and Dennis (Hendrickson, H.S., and Dennis, E.A. (1984) J. Biol. Chem. 259, 5734-5739). Vmax, Ks, and Km values obtained for various isomers and racemic mixtures of the synthetic thioester analogs are compared with corresponding oxyester substrates. Unnatural sn-1 isomers competitively inhibited the hydrolysis of natural sn-3 isomers of phosphatidylethanolamine and phosphatidic acid. Furthermore, the sn-1 isomer of phosphatidic acid was hydrolyzed by phospholipase A1, but with lower catalytic efficiency than the sn-3 isomer. The presence of a thioester at the sn-1 position did not change the Vmax significantly, as compared to the oxyester phospholipids. When two thioesters were present on the phospholipid molecule, the Vmax was decreased significantly. A convenient synthesis of 1-monothioester analogs of phospholipids is reported. The results presented show the usefulness of the spectrophotometric assay for measuring phospholipase A1 activity as well as the influence of racemic mixtures and thioesters on the hydrolytic rate.

Animals↗
PubMed1988

Stimulus-response coupling in marine sponge cell aggregation: lipid metabolism and the function of exogenously added arachidonic and docosahexaenoic acids.

Cells of the marine sponge, Microciona prolifera, the most ancient of the animal cells which clump on recognition, resemble neutrophils and platelets in undergoing stimulus-response coupling when exposed to Ca2+ ionophores and phorbol esters. We have studied lipid content and remodelling in sponge cells by thin-layer, gas-liquid, and high-performance liquid chromatography (HPLC) analyses supplemented by ultraviolet and mass spectroscopy. Phosphatidylcholine (PC) (35.6%), phosphatidylethanolamine (PE) (27.4%) and phosphatidylserine (PS) (21.4%) constituted the bulk of phospholipids detected. The major fatty acids were all polyenoic; 22:6 (22%), 26:2 (17%) and 26:3 (15%). Arachidonic acid (20:4), present as 2.7% of total phospholipid, and docosahexanoic acid (22:6) were found to elicit aggregation of sponge cells when added (10 microM) in synergy with ionomycin (1 microM), resembling in their effects those of phorbol esters (but not phorbol) and 1-oleyl-2-acetylglycerol (OAG). Moreover, 20:4 and 22:6, as well as phorbol ester and OAG, overcame the block to aggregation imposed by colchicine and vinblastine. Kinetic studies of lipid remodelling showed that aggregating cells diverted [14C]22:6 or [14C]20:4 from triacylglycerol into diacylglycerol and phospholipids; appearance of label in phosphatidic acid and phosphatidylinositol (PI) anteceded labeling of phosphatidylcholine. In unstimulated cells, [14C]22:6 was rapidly incorporated into phosphatidylcholine with little accumulation in phosphatidate. Although 22:6 and 20:4 resembled OAG and phorbol esters in overcoming the effects of colchicine and vinblastine (which had no effects on overall lipid metabolism), they did not reverse the block to aggregation of nordihydroguaiaretic acid (NDGA) (which inhibited lipid metabolism). Under none of these circumstances was 22:6 or 20:4 converted to cyclooxygenase or lipoxygenase products in the course of aggregation: all labeled acyl groups remained present as unmodified fatty acids on alkaline hydrolysis. These data not only extend the observations of Muller et al. (J. Biol. Chem. 262 (1987) 9850-9858) on the role of phosphoinositides and C kinase in marine sponge cell aggregation, but also demonstrate that sponges form diacylglycerols in the process. We suggest that exogenous 22:6 and 20:4 (like phorbol esters or OAG) can substitute for endogenous diacylglycerol in the activation of protein kinase C.

Animals↗
PubMed1988

On the substrate specificity of rat liver phospholipase A1.

The substrate specificity of purified phospholipase A1 was studied using mixed micelles of phospholipid and Triton X-100. The kinetic analysis employed determined Vmax, Ks (a dissociation constant for the phospholipase A1-mixed micelle complex), and Km (the Michaelis constant for the catalytic step which reflects the binding of the enzyme to the substrate in the interface). The order of Vmax values was phosphatidic acid greater than phosphatidylethanolamine greater than phosphatidylcholine greater than phosphatidylserine. The order of Ks values was phosphatidylcholine greater than phosphatidylethanolamine greater than phosphatidic acid greater than phosphatidylserine; the order of Km values was phosphatidic acid greater than phosphatidylethanolamine = phosphatidylserine greater than phosphatidylcholine. When present together, phosphatidylcholine inhibited the hydrolysis of phosphatidylethanolamine but phosphatidylethanolamine did not affect the hydrolysis of phosphatidylcholine. Sphingomyelin, phosphatidylcholine plasmalogen, and phosphatidylethanolamine plasmalogen had no effect on the hydrolysis of phosphatidylethanolamine. The effects of the reaction products, lysolipids and/or fatty acids, were also considered for their influence on phosphatidylethanolamine hydrolysis catalyzed by phospholipase A1. Free fatty acid was found to inhibit, whereas lysophospholipids stimulated hydrolysis of phosphatidylethanolamine. In a mixture of 1,2- and 1,3-diacylglycerides in mixed micelles, only the acyl chain at the sn-1 position of the 1,2 compound was hydrolyzed. Surface charge did not modulate the hydrolysis of phosphatidylcholine vesicles or mixed micelles. In conclusion, it is hypothesized that steric hindrance at position 3 of the glycerol regulates substrate binding in the active site and that an acyl group in position 1 is favored over a vinyl ether linkage for binding.

Animals↗
PubMed1988

Stimulation of arachidonic acid release and prostaglandin synthesis by bryostatin 1.

The mechanism of tumor promotion may involve stimulation of prostaglandin production. Previous studies with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) have identified two effects of TPA on prostaglandin production. TPA stimulates both arachidonic acid release and de novo synthesis of prostaglandin H synthase. Activation of protein kinase C by TPA appears to be part of the mechanism to cause arachidonic acid release. However, it is unclear if induction of prostaglandin H synthase also involves activation of protein kinase C. Bryostatin 1 is known to activate protein kinase C and to mimic some of the effects of TPA. We compared bryostatin 1 with TPA for the ability to cause arachidonic acid release and induce synthesis of prostaglandin H synthase. Bryostatin 1 induced arachidonic acid release and caused some prostaglandin production but only marginally induced synthesis of prostaglandin H synthase. Furthermore, we found that bryostatin 1 could inhibit the effect of TPA both in stimulation of arachidonic acid release and in the induction of prostaglandin H synthase.

Animals↗