Sapintoxin A, a new biologically active nitrogen containing phorbol ester

Taylor, Stephen; Gafur, M. A.; Choudhury, A.K.; Evans, Fred J.

doi:10.1007/bf01967918

Cited by 33 publications

(17 citation statements)

References 5 publications

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“…In the present study, the binding of phorbol ester, diacylglycerol, and also the potent PKC activator, bryostatin-I (B-I), to recombinant PKC␣ was investigated using a highly sensitive binding assay based on the fluorescent phorbol ester, sapintoxin-D (SAPD) (28). Previous assays of phorbol ester binding have generally been based on the use of [ 3 H]PDBu.…”

Section: Protein Kinase C (Pkc)mentioning

confidence: 99%

Protein Kinase Cα Contains Two Activator Binding Sites That Bind Phorbol Esters and Diacylglycerols with Opposite Affinities

Slater

Kelly

et al. 1996

Journal of Biological Chemistry

110

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Based on marked differences in the enzymatic properties of diacylglycerols compared with phorbol esteractivated protein kinase C (PKC), we recently proposed that activation induced by these compounds may not be equivalent (Slater, S. J., Kelly, M. B., Taddeo, F. J., Rubin, E., and Stubbs, C. D. (1994) J. Biol. Chem. 269, 17160 -17165). In the present study, direct evidence is provided showing that phorbol esters and diacylglycerols bind simultaneously to PKC␣. Using a novel binding assay employing the fluorescent phorbol ester, sapintoxin-D (SAPD), evidence for two sites of high and low affinity was obtained. Thus, both binding and activation doseresponse curves for SAPD were double sigmoidal, which was also observed for dose-dependent activation by the commonly used phorbol ester, 4␤-12-O-tetradecanoylphorbol-13-acetate (TPA). TPA removed high affinity SAPD binding and also competed for the low affinity site. By contrast with TPA, low affinity binding of SAPD was inhibited by sn-1,2-dioleoylglycerol (DAG), while binding to the high affinity site was markedly enhanced. Again contrasting with both TPA and DAG, the potent PKC activator, bryostatin-I (B-I), inhibited SAPD binding to its high affinity site, while low affinity binding was unaffected. Based on these findings, a model for PKC activation is proposed in which binding of one activator to the low affinity site allosterically promotes binding of a second activator to the high affinity site, resulting in an enhanced level of activity. Overall, the results provide direct evidence that PKC␣ contains two distinct binding sites, with affinities that differ for each activator in the order: DAG > phorbol ester > B-I and B-I > phorbol ester > DAG, respectively. Protein kinase C (PKC)1 comprises a family of isozymes that are pivotal in intracellular signal transduction (1-4). Activation of PKC requires association with the membrane and is induced by a number of activators and cofactors, the requirements for which differ for each isoform (2). Thus, with the exception of the so called atypical PKC isoforms, the activity of membrane-associated PKC is potentiated by the second messenger, diacylglycerol, a product of hormone receptor-phospholipase C-catalyzed phospholipid hydrolysis.In addition to the natural activators, including diacylglycerol, the enzyme is activated with high specificity by the tumorpromoting phorbol esters (5). For this reason, phorbol esters are often used in the study of the mechanism of PKC activation, based on the assumption that they compete directly with diacylglycerols for a common binding site on the enzyme (6, 7). Also it is commonplace in studies of the regulation of cellular processes to infer PKC involvement from a response elicited by phorbol esters (5). However, a number of studies have provided evidence indicating that the activated conformational forms of PKC induced by diacylglycerol compared with phorbol esters may not be equivalent based on observations of marked differences in the biological (8, 9) and enzymatic properties (10 -1...

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Section: Protein Kinase C (Pkc)mentioning

confidence: 99%

Protein Kinase Cα Contains Two Activator Binding Sites That Bind Phorbol Esters and Diacylglycerols with Opposite Affinities

Slater

Kelly

et al. 1996

Journal of Biological Chemistry

110

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“…These data imply that casbene is biosynthesized in most organs of Jatropha, regardless of their developmental stages. Lathyrane-type diterpenes and phorbol were found in various tissues of other Euphorbiaceae plants, e.g., jatrowediol from J. weddelliana stems (Brum et al 2001), multi done from J. multi da stems (Das et al 2009), and sapintoxin A from unripe S. indicum fruit (Taylor et al 1981). us, the JcCSH gene is expected to be involved in the biosynthesis of a broad range of diterpenes, including phorbol.…”

mentioning

confidence: 99%

Characterization of the casbene synthase homolog from Jatropha (<i>Jatropha curcas</i> L.)

Nakano

Ohtani

Polsri

et al. 2012

Plant Biotechnology

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Abstracte high oil content of Jatropha (Jatropha curcas L.) seeds makes Jatropha an attractive resource for the production of sustainable bioenergy. However, the Jatropha seed kernels also contain antinutrients and various toxins that persist in the oil and seed cakes and pose a safety risk. Since phorbol esters (PEs) are the major contributor to toxicity, a better understanding of PE biosynthesis is expected to elucidate an e ective strategy for the utilization of Jatropha plants. In this study, a Jatropha curcas casbene synthase homolog (JcCSH) with high sequence similarity to casbene synthases (CSs) from Ricinus communis, Euphorbia esula, and Sapium sebiferum was cloned from Jatropha leaf tissue. CS has been hypothesized to catalyze the rst step of phorbol biosynthesis. JcCSH encodes a protein that contains a chloroplast transit peptide and a DDXXD motif that is conserved among known terpene cyclases. JcCSH was expressed in seedlings, mature leaves, and the esh of developing fruits, but not in developing seeds. Our results suggest that JcCSH is widely involved in casbene biosynthesis in various tissues other than seeds. Key words:Casbene synthase, Jatropha (Jatropha curcas L.), phorbol ester.Recently, Jatropha (Jatropha curcas L.) has attracted much attention as a potential resource for the production of sustainable bioenergy, following concerns about the depletion of fossil fuels and global warming. Jatropha, a perennial shrub that originated in Mexico and Central America and belongs to the Euphorbiaceae family, is widely distributed between the tropics of Cancer and Capricorn.e seed kernels are rich in oil (44-62%) and proteins (22-35%), making this plant a favorable feedstock not only for biodiesel but also for protein (Makkar et al. 1998). However, it is hard to utilize the Jatropha seed cakes for animal feed a er extracting the oil, because several antinutrients and various toxins, such as curcin, trypsin inhibitors, and phorbol esters (PEs), are contained in the seed kernels (Makkar et al. 1998). Among these harmful substances, the major contributor to toxicity is PEs (Makkar et al. 1998). PEs are tetracyclic diterpenoids that occur in the seeds, sap, and latex of plants of the ymelaeaceae and Euphobiaceae families. Six PE derivatives were identified from Jatropha oil and their structures were solved by nuclear magnetic resonance (NMR) analysis. They were all found to contain 12-hydroxy-16-deoxyphorbol (Adolf et al. 1984;Haas et al. 2002). Since a PE isolated from Jatropha is known to have tumor-promoting activity (Hirota et al. 1988), it is critical to eliminate the risk of PEs toxicity if Jatropha is to be used commercially. One e ective means of doing so is to shut down and/or modify the biosynthesis of PEs at the molecular level.PEs are composed of a tetracyclic diterpene, named tiglian, and two fatty acids, which are esterified to C13 and C16 of the tiglian skeleton (Haas et al. 2002). The biosynthetic pathway of PEs is currently poorly understood. The only presumed step is the first cyclization of...

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“…Sapatoxin A [35] isolated from Sapium indicum is identical with Euphorbia factor Tij. 12-0-[(2Z, 4£)-2,4-octadienoyl]-4-deoxyphorbol-13-acetate was isolated from E. tirucalli latex collected in Colombia [37].…”

Section: Discussionmentioning

confidence: 99%

“…Subsequent to the first identification of the chemi cal structure of the diterpene parent 4-deoxyphorbol [23] derivatives thereof have been found in various Euphorbiaceae [33][34][35][36]. Sapatoxin A [35] isolated from Sapium indicum is identical with Euphorbia factor Tij.…”

Section: Discussionmentioning

confidence: 99%

On the Active Principles of the Spurge Family (Euphorbiaceae) XI. [1] The Skin Irritant and Tumor Promoting Diterpene Esters of Euphorbia tirucalli L. Originating from South Africa

Fürstenberger

Hecker

1985

Zeitschrift Für Naturforschung C

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The irritant and tum or-prom oting constituents o f latex of Euphorbia tirucalli L. originating from South Africa were isolated. They were identified as irritant ingenane and tigliane type diterpene esters derived from unsaturated aliphatic acids and acetic acid and the polyfunctional diterpene parent alcohols 4-deoxyphorbol, phorbol and ingenol, respectively. The irritant and tum or-prom oting esters of 4-deoxyphorbol are predominant and were fully characterized chem ically and biologically. They are positionally isomeric 12,13-acylates, acetates e.g. Euphorbiafactors T i,-Ti4. A s acyl groups they carry hom ologous, highly unsaturated alipha tic acids o f the general structure C H 3 -(C H 2)m -(CH = CH)" -CO O H (m = 2,4; « = 1,2, 3,4,5; N = 2n + m + 2). C orresponding diesters o f 4-deoxy-4a-phorbol are also present which are biologi cally inactive. Com parison o f structures and biological activities o f 12,13-diesters o f 4-deoxyphorbol indicates that -for a distinct total number o f C-atoms (N) in the acyl m oiety -an increasing number of conjugated double bonds (n) may increase the irritant but decrease the tum or-prom ot ing activity. R eplacem ent o f the hydroxyl function at C-4 (phorbol-12,13-diesters) by hydrogen (corresponding 4-deoxyphorbol-12,13-diesters) does not essentially alter biological activities. Epim erization o f 4-deoxyphorbol-12,13-diesters at C-4 abolishes biological activities.The specific chem ical properties dem onstrated for the diterpene ester irritants contained in the latex o f E. tirucalli and hence in all plant parts may be useful in trials to abolish the potential risk of cancer involved especially in occupational mass production and handling o f the plant. Som e of the structure activity relations o f the Euphorbia factors isolated made them excellent tools in experim ental cancer research for the analysis o f mechanisms of tum origenesis.

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Sapintoxin A, a new biologically active nitrogen containing phorbol ester

Cited by 33 publications

References 5 publications

Protein Kinase Cα Contains Two Activator Binding Sites That Bind Phorbol Esters and Diacylglycerols with Opposite Affinities

Protein Kinase Cα Contains Two Activator Binding Sites That Bind Phorbol Esters and Diacylglycerols with Opposite Affinities

Characterization of the casbene synthase homolog from Jatropha (<i>Jatropha curcas</i> L.)

On the Active Principles of the Spurge Family (Euphorbiaceae) XI. [1] The Skin Irritant and Tumor Promoting Diterpene Esters of Euphorbia tirucalli L. Originating from South Africa

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