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Biomedical subjects

J A Jakubowski

Publications and source records attributed to J A Jakubowski.

At least 19 recordsLinked to original sources
PubMed2000

Fused bicyclic Gly-Asp beta-turn mimics with potent affinity for GPIIb-IIIa. Exploration of the arginine isostere.

6-[4-Amidinobenzoyl]amino]-tetralone-2-acetic acid is a potent antagonist of GPIIb-IIIa. Substitution in the meta position of the benzamidine, or replacement with a heteroaryl amidine was tolerated in this series. Use of an acyl-linked 4-alkyl piperidine as an arginine isostere also provided active compounds. Compounds from this series provided substantial systemic exposure in the rat following oral administration.

Acetates↗
PubMed1998

Development of dual-acting agents for thromboxane receptor antagonism and thromboxane synthase inhibition. 3. Synthesis and biological activities of oxazolecarboxamide-substituted omega-phenyl-omega-(3-pyridyl)alkenoic acid derivatives and related compounds.

A novel series of oxazolecarboxamide-substituted omega-phenyl-omega-(3-pyridyl)alkenoic acid derivatives was discovered as potent dual-acting agents to block the TXA2 receptor and to inhibit the thromboxane synthase (TRA/TSI). Synthesis, structure-activity relationship (SAR), and in vitro and in vivo pharmacology of this series of compounds are described. Modification of the series revolved around the oxazole moiety to increase the hydrophilicity of the compounds and to correlate the biological activity with lipophilicity of the compounds. The most potent in the series was (E)-7-[4-[4-[[(4-cyclohexylbutyl)amino]carbonyl]-2-oxazolyl] phenyl]-7 -(3-pyridyl)hept-6-enoic acid (14) with Kd = 9.9 +/- 0.4 nM for the thromboxane receptor antagonism and IC50 = 55.0 +/- 17.9 nM for thromboxane synthase inhibition. The compound 14 was a selective TRA/TSI which exhibited desirable characteristics for oral activity, "shunt" effect to elevate PGI2 level, and absence of agonist activity.

Animals↗
PubMed1998

Development of dual-acting agents for thromboxane receptor antagonism and thromboxane synthase inhibition. 2. Design, synthesis, and evaluation of a novel series of phenyl oxazole derivatives.

Synthesis and initial in vitro evaluation of a novel series of phenyl oxazole derivatives are described. An SAR study of the novel dual-acting TRA/TSI agent has revealed that the lipophilicity of the oxazole amide substituents greatly influences the TRA activity but not the TSI. The chain length of the alkenoic acid side chain affects both TRA and TSI. The optimal chain length for the combined activities was found to be n = 4 (heptenoic acid).

Drug Design↗
PubMed1998

Intravenous administration of the glycoprotein IIb-IIIa receptor antagonist 7E3 induces reperfusion of an acute thrombotic occlusion of the canine coronary artery.

The ability of the F(ab')2 fragment of the murine monoclonal antibody 7E3 directed against the platelet glycoprotein IIb-IIIa receptor complex, to cause reperfusion of a totally occluding coronary artery thrombus was examined alone and in combination with aspirin and heparin in a canine model of coronary artery thrombosis. A localized thrombus was produced in the left circumflex coronary artery in open-chest dogs by electrolytic injury of the endothelium. Intravenous administration of a single injection of 5.0 mg/kg aspirin and heparin (80 U/kg bolus plus 30 U/kg/hr x 2 hr) maintained vessel patency for approximately 101 +/- 15 minutes. After vessels had been completely occluded for 5 minutes (in the presence of aspirin + heparin), a single intravenous injection of saline (10 ml) or 0.8 mg/kg 7E3 was administered. Reperfusion was observed in all dogs (6 of 6) receiving 7E3; 4 of 6 dogs maintained vessel patency throughout the course of the 2 hour observation period. Activated partial thromboplastin and thrombin times were elevated 1.4 and 9 fold, respectively, in groups that received heparin. Template bleeding times were significantly elevated in the groups receiving 7E3. In the control group, 2 of 5 dogs reperfused briefly, however neither were patent at the end of the observation period. A third group of 4 dogs which did not receive the aspirin + heparin regimen was allowed to occlude and 5 minutes later received a single intravenous injection of 0.8 mg/kg 7E3. None of the 4 dogs in this group reperfused at any time during the study. There were no significant differences between groups in regards to hematological or hemodynamic measurements during the experiment. We concluded from these findings that the monoclonal antibody, 7E3 can promote the dissolution of friable coronary artery thrombi that evolve during standard anticoagulant and antiplatelet therapy.

Abciximab↗
PubMed1998

Effects of beta3-integrin blockade (c7E3) on the response to angioplasty and intra-arterial stenting in atherosclerotic nonhuman primates.

Because the beta3-antagonist abciximab (c7E3 Fab) has significantly improved late outcomes after coronary angioplasty, the beta3 integrins have been implicated in the arterial response to injury. However, the mechanisms underlying this benefit are unknown. The observation that c7E3 binds beta3 integrins on vascular cells (alphavbeta3) with affinity equal to that for the platelet glycoprotein IIb/IIIa integrin has led to the hypothesis that c7E3 may act directly on the artery wall to prevent restenosis after angioplasty. To test this hypothesis, we studied the effects of c7E3 on structural changes within the artery wall after angioplasty or stent angioplasty in 23 male cynomolgus monkeys with established atherosclerosis. Animals were randomly assigned to receive either a bolus of c7E3 (0.4 mg/kg IV, n=11) followed by a 48-hour infusion (0. 2 microg. kg-1. min-1) or an equal volume of vehicle (n=12). Animals received weight-adjusted aspirin and heparin and then underwent unilateral iliac artery experimental angioplasty and subclavian artery stent angioplasty (Palmaz). Iliac artery lumen diameter (LD) was determined by angiography at baseline (LDPre), after angioplasty (LDPost), and 35 days later (LDDay35). Arteries were then fixed by perfusion and removed for analysis. Lumen, intima, media, and external elastic lamina (EEL) areas were measured in iliac artery cross sections. Values from each injured iliac artery were normalized to the contralateral uninjured iliac artery to control for interanimal variability in baseline artery size and atherosclerosis extent. Intimal area was also measured in subclavian stent cross sections. c7E3 blocked platelet aggregation and prolonged the bleeding time from 2.8+/-1.1 to 19.8+/-2.5 minutes, P<0.001. Experimental angioplasty increased LDPost an average of 28%, and the initial gain was similar in both groups (P=NS). Despite an anti-platelet effect, c7E3 did not inhibit iliac lumen narrowing (LDDay35-LDPost: c7E3, -0.69+/-0.17 versus vehicle, -0.99+/-.17 mm, P=0.35); intimal hyperplasia (neointima area: c7E3, 1.12+/-.28 versus vehicle, 1.22+/-.20 mm2, P=0.77); or decrease in artery wall size (EEL area [percent of uninjured control]: c7E3, 101+/-7% versus vehicle, 121+/-7%). Stent intimal hyperplasia was also unaltered by c7E3 treatment (neointimal area: c7E3, 1.09+/-0.16 versus vehicle, 1. 28+/-0.11 mm2, P=0.36). These results suggest that the benefits of c7E3 treatment in coronary angioplasty were not from inhibition of intimal hyperplasia or improved artery wall remodeling. Alternative mechanisms should be explored to explain improved late outcomes after angioplasty in patients treated with c7E3.

Abciximab↗
PubMed1998

Quantitative detection of platelet GPIIb-IIIa receptor antagonist activity using a flow cytometric method.

Platelet-membrane surface receptors are important targets for pharmacologic intervention in cardiovascular disease. Among these, glycoprotein (GP) IIb-IIIa is dominant and integrally involved in platelet aggregation and thrombus formation. When activated, GPIIb-IIIa binds soluble fibrinogen (Fb) in a key, early step of this process. New drugs are under development that block Fb binding to GPIIb-IIIa and inhibit platelet aggregation. A thorough understanding of the relationship between circulating drug levels and the extent of GPIIb-IIIa receptor occupancy in humans is crucial for safe and efficacious use of these agents. Described here is the development of a new technique for measurement of GPIIb-IIIa receptor occupancy. In this assay, activated human platelets are incubated with biotinylated fibrinogen (Fb-biotin) followed by antibiotin-FITC.The extent of Fb binding is determined using flow cytometric analysis. Our results indicate that Fb-biotin binds rapidly to activated platelets and its detection is dependent on incubation temperature. Platelets that were pre-incubated with the GPIIb-IIIa antagonist echistatin were inhibited from binding Fb-biotin in a concentration-dependent manner. The fluorescence of processed samples was stable for two weeks in the cold. The assay described here is simple, cost effective, and can be adapted for use in clinical evaluations of these new drugs.

Biotin↗
PubMed1997

Fibrinogen receptor (GPIIb-IIIa) antagonists derived from 5,6-bicyclic templates. Amidinoindoles, amidinoindazoles, and amidinobenzofurans containing the N-alpha-sulfonamide carboxylic acid function as potent platelet aggregation inhibitors.

A series of highly potent and specific fibrinogen receptor antagonists have been discovered and optimized through structural modification of the novel amidinoindole and benzofuran compounds, I and II. Systematic linker optimization afforded the amidinobenzofuran-containing inhibitor 29, which displayed an IC50 value of 250 nM in platelet aggregation assays. Attempts to enhance activity by modification of the beta-position of the beta-alanyl carboxylate group of 29 had only a modest effect on inhibitory activity in aggregation assays. Analogues prepared to enhance the activity by conformational restriction were also found to be equally or less potent. In contrast, modification at the alpha-position of the beta-alanyl carboxylate group resulted in the identification of extremely potent and novel amidinobenzofuran-containing derivatives 46-49. Reexamination of 5,6-bicyclic aromatic nucleus led to the further identification of amidinoindole- and amidinoindazole-containing derivatives 53-55. These analogues, 46-49 and 53-55, exhibited potent in vitro activity with IC50 values of 25-65 nM in platelet aggregation assays and an IC50 value of 2 nM in fibrinogen binding assays and demonstrated a selectivity of > 50,000-fold for GPIIb-IIIa versus the most closely related integrin, the vitronectin receptor, alpha v beta 3.

Administration, Oral↗
PubMed1997

Human group II 14 kDa phospholipase A2 activates human platelets.

Recombinant human group II phospholipase A2 (sPLA2) added to human platelets in the low microg/ml range induced platelet activation, as demonstrated by measurement of platelet aggregation, thromboxane A2 generation and influx of intracellular free Ca2+ concentration and by detection of time-dependent tyrosine phosphorylation of platelet proteins. The presence of Ca2+ at low millimolar concentrations is a prerequisite for the activation of platelets by sPLA2. Mg2+ cannot replace Ca2+. Mg2+, given in addition to the necessary Ca2+, inhibits sPLA2-induced platelet activation. Pre-exposure to sPLA2 completely blocked the aggregating effect of a second dose of sPLA2. Albumin or indomethacin inhibited sPLA2-induced aggregation, similarly to the inhibition of arachidonic acid-induced aggregation. Platelets pre-treated with heparitinase or phosphatidylinositol-specific phospholipase C lost their ability to aggregate in response to sPLA2, although they still responded to other agonists. This suggests that a glycophosphatidylinositol-anchored platelet-membrane heparan sulphate proteoglycan is the binding site for sPLA2 on platelets. Previous reports have stated that sPLA2 is unable to activate platelets. The inhibitory effect of albumin and Mg2+, frequently used in aggregation studies, and the fact that isolated platelets lose their responsiveness to sPLA2 relatively quickly, may explain why the platelet-activating effects of sPLA2 have not been reported earlier.

Arachidonic Acid↗
PubMed1997

Effect of Ca2+ on GP IIb-IIIa interactions with integrilin: enhanced GP IIb-IIIa binding and inhibition of platelet aggregation by reductions in the concentration of ionized calcium in plasma anticoagulated with citrate.

BACKGROUND: Integrilin (eptifibatide), a potent inhibitor of the fibrinogen binding function of GP IIb-llla, has been shown to reduce the thrombotic complications of angioplasty and of acute coronary syndromes. The present study was designed to determine whether the reduced Ca2+ concentrations in plasma anticoagulated with citrate affect Integrilin binding to GP IIb-IIIa and the ex vivo pharmacodynamic measurements for this drug. METHODS AND RESULTS: Lower concentrations of Integrilin were found to inhibit platelet aggregation in plasma anticoagulated with citrate (for ADP, mean+/-SD IC(50)=140+/-40 nmol/L, n=6; Ca2+ =40 to 50 micromol/L) than with PPACK (IC(50)=570+/-70 nmol/L, P<.0001, n=6; Ca2+ approximately 1 mmol/L). Chelation of Ca2+ with EDTA or citrate caused a similar degree of enhancement in the inhibitory activity of Integrilin. Measurements of D3 LIBS epitope expression showed that the enhanced inhibitory activity was caused by enhanced GP IIb-IIIa occupancy by Integrilin. Citrate anticoagulation decreased the amounts of Integrilin required to inhibit the binding of PAC1, a monoclonal antibody that mimics the GP IIb-IIIa binding activity of fibrinogen. Reduced Ca2+ also increased Integrilin inhibition of the binding of biotinylated fibrinogen to purified, immobilized GP IIb-IIIa. CONCLUSIONS: These data suggest that citrate anticoagulation removes Ca2+ from GP IIb-IIIa and enhances the apparent inhibitory activity of Integrilin. This finding indicates that the inhibitory activity of Integrilin is overestimated in blood samples collected with citrate, suggesting that it may be possible to achieve greater antithrombotic efficacy beyond that observed in clinical trials to date with Integrilin.

Antibodies, Monoclonal↗
PubMed1997

Use of conformationally restricted benzamidines as arginine surrogates in the design of platelet GPIIb-IIIa receptor antagonists.

The use of 5,6-bicyclic amidines as arginine surrogates in the design of a novel class of potent platelet glycoprotein IIb-IIIa receptor (GPIIb-IIIa) antagonists is described. The additional conformational restriction offered by the bicyclic nucleus results in 20-400-fold increases in potency compared to the freely flexible, acyclic benzamidine counterpart. The design, synthesis, structure-activity relationships (SAR), and in vitro activity of this novel class of GPIIb-IIIa antagonists are presented.

Arginine↗
PubMed1997

Non-peptide RGD surrogates which mimic a Gly-Asp beta-turn: potent antagonists of platelet glycoprotein IIb-IIIa.

Cyclic heptapeptide 1, which contains an Arg-Gly-Asp sequence, has good affinity for the platelet receptor GPIIb-IIIa and was chosen for study by 1H NMR techniques. The key RGD sequence of this molecule was found to reside in a conformationally defined type II' Gly-Asp beta-turn, and this information was used in the design of simple non-peptide RGD mimics. Disubstituted isoquinolones, bearing an acidic side chain at position 2 and a basic side chain at position 6, were prepared and were found to have modest affinity for GPIIb-IIIa. Systematic modification of the basic residue contained in these molecules yielded compounds with high affinity for GPIIb-IIIa.

Aspartic Acid↗
PubMed1996

p38 mitogen-activated protein kinase phosphorylates cytosolic phospholipase A2 (cPLA2) in thrombin-stimulated platelets. Evidence that proline-directed phosphorylation is not required for mobilization of arachidonic acid by cPLA2.

The Ca2+-sensitive 85-kDa cytosolic phospholipase A2 (cPLA2) is responsible for thrombin-stimulated mobilization of arachidonic acid for the synthesis of thromboxane A2 in human platelets. We have previously shown that thrombin activates p38 kinase, a recently discovered new member of the mitogen-activated protein kinase family (Kramer, R. M., Roberts, E. F., Strifler, B. A., and Johnstone, E. M. (1995) J. Biol. Chem. 270, 27395-27398) and also induces phosphorylation of cPLA2, thereby increasing its intrinsic catalytic activity. In the present study we have examined the role of p38 kinase in the phosphorylation and activation of cPLA2 in stimulated platelets. We have observed that activation of p38 kinase accompanies receptor-mediated events in platelets and coincides with cPLA2 phosphorylation. Furthermore, in the presence of inhibitors of p38 kinase, the proline-directed phosphorylation of cPLA2 was completely blocked in platelets stimulated with the thrombin receptor agonist peptide SFLLRN and was suppressed during the early (up to 2 min) phase of platelet stimulation caused by thrombin. Unexpectedly, we found that prevention of proline-directed phosphorylation of cPLA2 in stimulated platelets did not attenuate its ability to release arachidonic acid from platelet phospholipids. We conclude that: 1) cPLA2 is a physiological target of p38 kinase; 2) p38 kinase is involved in the early phosphorylation of cPLA2 in stimulated platelets; and 3) proline-directed phosphorylation of cPLA2 is not required for its receptor-mediated activation.

Arachidonic Acid↗
PubMed1995

Differential activation of cytosolic phospholipase A2 (cPLA2) by thrombin and thrombin receptor agonist peptide in human platelets. Evidence for activation of cPLA2 independent of the mitogen-activated protein kinases ERK1/2.

The thrombin receptor agonist peptide SFLLRN was less effective than thrombin in eliciting the liberation of arachidonic acid and the generation of thromboxane A2 by human platelets. We found that while SFLLRN evokes an initial transient increase in cystolic free calcium concentration ([Ca2+]i) of similar magnitude as that caused by thrombin, the SFLLRN-induced elevation of [Ca2+]i declines more rapidly to near resting levels than that evoked by thrombin, suggesting that disparate levels of [Ca2+]i may contribute to the attenuated arachidonic acid release. Furthermore, we observed that SFLLRN is less effective than thrombin in mediating the "activating" phosphorylation of cytolic phospholipase A2 (cPLA2). Both thrombin and SFLLRN rapidly and transiently activated kinases that phosphorylate the 21-residue synthetic peptide Thr669 derived from the epidermal growth factor receptor, but the maximal activation of proline-directed kinases by SFLLRN was less pronounced than that by thrombin. MonoQ chromatography and immunoblot analysis of extracts from stimulated platelets revealed that while thrombin induced a prominent activation of the mitogen-activated protein kinases ERK1 and ERK2, SFLLRN completely failed to do so. On the other hand, SFLLRN, like thrombin, stimulated the activity of a proline-directed kinase distinct from ERK1/2, but the activation of this kinase was less pronounced following stimulation of platelets with SFLLRN compared with thrombin. We conclude 1) that the partial activation of cPLA2 and the subsequent attenuated mobilization of arachidonic acid in response to SFLLRN may be the consequence of a less prolonged elevation of [Ca2+]i and insufficient activation of proline-directed kinase(s) by SFLLRN and 2) that the ability of SFLLRN to mediate the activating phosphorylation of cPLA2 in the absence of ERK1/2 stimulation suggest that, at least in human platelets, proline-directed kinases other than ERK1/2 may phosphorylate and activate cPLA2.

Amino Acid Sequence↗
PubMed1995

In vivo effects of a novel thromboxane A2/prostaglandin H2 (TXA2/PGH2) partial agonist, (+)5(Z)-7-[3-endo-phenylsulfonylamino[2.2.1]- bicyclohept-2-exo-yl]-heptenoic acid [(+)-S-145], on vascular, platelet and cardiac function.

A novel thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor ligand, (+)5(Z)-7-[3-endo-phenylsulfonylamino[2.2.1]-bicyclohept-2-e xo- yl]-heptenoic acid [(+)-S-145], was evaluated in guinea pigs to assess the in vivo pharmacodynamic profile of this compound at vascular, cardiac and platelet TXA2/PGH2 receptors. Comparison was made to the TXA2/PGH2 receptor antagonist SQ29548. Upon i.v. injection, (+)-S-145, but not SQ29548, elicited transient (approximately 1 min) increases in mean arterial blood pressure (ED50 +/- 95% confidence limit = 6.1 + 4.0, -2.2 micrograms/kg). The potency of i.v. (+)-S-145 (ID50 = 6.3 + 2.3, -2.3 micrograms/kg) against the pressor response to subsequent i.v. TXA2/PGH2 mimetic, U44069, was 9.5-fold greater than that of SQ29548 (ID50 = 59.1 + 52.9, - 52.9 micrograms/kg). Intravenous (+)-S-145 inhibited U44069-induced decreases in circulating platelet count (ID50 = 4.2 + 4.1, - 2.0 micrograms/kg). In thoracotomized guinea pigs, i.v. (+)-S-145 (31.6 micrograms/kg) and increasing i.v. doses of U44069 increased mean arterial blood pressure, total peripheral resistance, left ventricular end-diastolic pressure and left ventricular peak positive dP/dt (LV + dP/dt) and depressed cardiac output (P < .05). Pretreatment with i.v. (+)-S-145 (31.6 micrograms/kg) abolished these U44069-induced effects. In thoracotomized guinea pigs in which left ventricular end-diastolic pressure and HR were held constant, U44069 again increased LV + dP/dt (P < .05), but (+)-S-145 decreased LV + dP/dt (P < .05), which indicates the lack of an (+)-S-145 direct inotropic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Biochemical and pharmacological activity of arene-fused prostacyclin analogues on human platelets.

Human platelets have been employed as an assay system to evaluate the pharmacological activity of a group of stable, arene-fused prostacyclin analogs. Prostacyclin (PGI2) is a highly active member of the eicosanoid family and is relatively unstable under physiological conditions. Prostacyclin's best characterized activities are those of inhibition of platelet aggregation and relaxation of vascular smooth muscle. These activities are mediated in large part via elevation of intracellular levels of cyclic AMP subsequent to receptor occupation and activation of adenylate cyclase. We previously described the synthesis of a series of arene-fused prostacyclin analogs with stability in aqueous media at physiological pH. Several of these compounds have prostacyclin-like activities, i.e., competitive binding at the platelet prostacyclin receptor, elevation of intraplatelet cyclic AMP levels and inhibition of human platelet aggregation. One compound in particular (11a) demonstrated these activities with potency similar to PGI2, i.e., Kd at platelet receptor of 3.7 nM and IC50 for inhibition of collagen-induced human platelet aggregation in plasma of 2.9 nM.

Blood Platelets↗
PubMed1994

Development of dual-acting agents for thromboxane receptor antagonism and thromboxane synthase inhibition--I. Synthesis, structure-activity relationship, and evaluation of substituted omega-phenyl-omega-(3-pyridyl)alkenoic acids.

A series of arylsulfonamido-substituted omega-phenyl-omega-(3-pyridyl)alkenoic acids were synthesized and evaluated in vitro for their ability to act as both a thromboxane A2 receptor antagonist (TRA) and thromboxane synthase inhibitor (TSI). Variations of alkenoic acid chain length, olefin geometry, substituent effect on the benzenesulfonamido group, and conformational flexibility of the substituted arylsulfonamido group were examined. Among the various substituents, iodo-substitution gave the most potent compound. Conformational flexibility between the arylsulfonamido group and the phenyl ring attached to the alkenoic acid side chain significantly enhanced the dual activities. The compound (E)-21c was identified as the most potent TRA/TSI (TRA: Kd = 53 nM; TSI: IC50 = 23 nM) in the series studied. The compounds 9c and 10c have indicated that these series of compounds are orally active and are specific TSIs as exhibited by the so-called 'shunt' effect on prostacyclin synthesis in vitro.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Thrombin-induced phosphorylation and activation of Ca(2+)-sensitive cytosolic phospholipase A2 in human platelets.

Receptor-mediated activation of human platelets by thrombin initiates a series of rapid biochemical events that include activation of phospholipase A2 to liberate arachidonic acid for further conversion to thromboxane A2. The identity of the phospholipase A2 involved has not been clear. Here we show by immunochemical analysis that human platelets contain significant amounts (60 ng/10(9) platelets) of the recently identified Ca(2+)-sensitive cytosolic phospholipase A2 (cPLA2). Metabolic labeling of human platelets with 33Pi revealed that the extent of phosphorylation of cPLA2 was greatly increased after thrombin treatment. Upon stimulation of platelets with thrombin, cPLA2 exhibits enhanced catalytic activity, as well as a change in its electrophoretic and chromatographic properties compared with cPLA2 in resting platelets. These alterations of cPLA2 are reversed by treatment with phosphatase, demonstrating that they are the consequence of thrombin-stimulated phosphorylation. Thrombin-induced phosphorylation and activation of cPLA2 is rapid (half-maximal by 1 min at 1 unit/10(9) platelets) and dose-dependent. Agonist-induced phosphorylation of cPLA2 is more sensitive to thrombin than the generation of thromboxane A2, suggesting that it may be an early event in the sequence of steps leading to the mobilization and further metabolism of arachidonic acid. By comparing the functional properties of cPLA2 from control versus thrombin-stimulated platelets, we found that while activated cPLA2 exhibits the same Ca2+ requirement and apparent substrate affinity (Km), its catalytic activity (Vmax) is increased compared with control cPLA2. We conclude that 1) cPLA2 is likely to play an important role in agonist-induced mobilization of arachidonic acid and 2) thrombin elicits rapid and full activation of cPLA2 not only by promoting a rise in cytosolic free Ca2+ but also by inducing phosphorylation of cPLA2 thereby improving its catalytic activity.

Amino Acid Sequence↗