Inactivation of bee venom phospholipase A2 by a sesquiterpene furanoic acid marine natural product.

A sesquiterpene furanoic acid (SFA) marine natural product isolated from soft corals of the genus Sinularia (Bowden et al., Aust J Chem 36: 371-376, 1983) was found to inactivate bee venom phospholipase A2 (bvPLA2, EC 3.1.1.4) in vitro. In this study, we characterized the kinetics of inactivation of bvPLA2 by this compound. The apparent IC50 value was 0.5 microM, and the inactivation of bvPLA2 was time dependent. The drug-enzyme binding appeared to be of a non-competitive, high-affinity nature that was irreversible by aqueous dialysis. The inactivation was prevented by the simultaneous addition of excess lysophosphatidylcholine (lysoPC) during the initial binding step, suggesting that modification of the enzyme by SFA occurs at or near the substrate binding site. Activation of bvPLA2 was observed with lysoPC addition at concentrations equimolar to bvPLA2 and higher. Saturation of activation occurred at concentrations greater than 10 microM lysoPC, and preincubation of bvPLA2 with 100 microM lysoPC did not inhibit the enzyme. Analysis of the post-incubation mixture of SFA-inhibited enzyme in the presence of lysoPC revealed the presence of unaltered enzyme exhibiting typical Michaelis-Menten kinetics. The significance of these observations is discussed in light of the recent discussion by Ortiz on the manoalide binding site on bvPLA2.

Saethre-Chotzen syndrome with familial translocation at chromosome 7p22.

Chromosome analysis of a male infant and his mother with Saethre-Chotzen syndrome demonstrated an apparently balanced translocation, t(2;7)(p23;p22). This association lends support to localization of the gene for Saethre-Chotzen syndrome to the 7p2 region and supports further involvement of gene(s) in the 7p22 region.

Selective inhibition of cytokinesis in sea urchin embryos by the marine natural product pseudopterolide.

Low concentrations (1-10 microM) of the marine natural product pseudopterolide inhibited cytokinesis and induced formation of multinucleate cells in fertilized Strongylocentrotus purpuratus embryos. As determined by immunofluorescence microscopy using fluorescent stains for actin filaments, microtubules, and chromosomes, pseudopterolide inhibited cytokinesis selectively by disrupting the contractile ring, whereas spindle microtubule organization and mitotic chromosome segregation to opposite spindle poles were unimpaired. At somewhat higher concentrations (16-20 microM), pseudopterolide induced formation of microtubule spiral asters, which are believed to be caused by rotation of the cytoplasm relative to the cell cortex. The effects of pseudopterolide on cytokinesis were cell-cycle dependent. The actions of pseudopterolide in fertilized sea urchin embryos were strikingly similar to the actions of another marine natural product, stypoldione, a structurally unrelated orthoquinone that reacts covalently with the sulfhydryl groups of glutathione, beta-mercaptoethanol, cysteine, and a number of proteins [Mol. Pharmacol. 35:635-642 (1989)]. In the present study, pseudopterolide was also found to react with sulfhydryl groups of glutathione, beta-mercaptoethanol, and cysteine. The results indicate that the cellular target for pseudopterolide, like the target for stypoldione, may be an especially sensitive sulfhydryl-containing protein involved in the formation or function of the contractile ring.

Structure and stereochemistry of brianolide, a new antiinflammatory diterpenoid from the Okinawan gorgonian Briareum sp.

Brianolide (1), a new antiinflammatory diterpenoid of the briarein class, possessing a beta substituent at C-12 (R), has been isolated from the Okinawan gorgonian Briareum sp. Its structure has been established from spectral data in conjunction with a single crystal X-ray analysis.