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Dinophysistoxin 1 (DTX1, 1) and okadaic acid (OA, 2), produced by the dinoflagellates Dinophysis spp. and Prorocentrum spp., are primary diarrhetic shellfish toxins (DSTs), which may cause gastric illness in people consuming such as bivalves. Both compounds convert to dinophysistoxin 3 (DTX3, 3; generic name for 1 and 2 with fatty acids conjugated at 7-OH) in bivalves. The enzyme okadaic acid O-acyl transferase (OOAT) is a membrane protein found in the microsomes of the digestive glands of bivalves. In this study, we established an in vitro enzymatic conversion reaction using 4-nitro-2,1,3-benzoxadiazole (NBD)-OA (4), an OA derivative conjugated with (R)-(-)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (NBD-APy) on 1-CO2H, as a substrate. We detected the enzymatically produced 3, NBD-7-O-palmitoyl-OA (NBD-Pal-OA), using high-performance liquid chromatography-fluorescence detection. We believe that an OOAT assay using 4 will facilitate the fractionation and isolation of OOAT in the future., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

Natural products containing the highly unusual phosphotriester ring are known to be potent serine hydrolase inhibitors. The long-chain bicyclic enol-phosphotriester salinipostins (SPTs) from the marine actinomycete Salinispora have been identified as selective antimalarial agents. A potential regulatory function has been suggested for phosphotriesters based on their structural relationship with actinomycete signaling molecules and the prevalence of spt-like biosynthetic gene clusters across actinomycetes. In this study, we established a mass spectrometry-guided screening method for phosphotriesters focusing on their characteristic fragment ions. Applying this screening method to the SPT producer Salinispora tropica CNB-440, new SPT analogs (4-6) were discovered and their structures were elucidated by spectroscopic analyses. Previously known and herein-identified SPT analogs inhibited the activity of human monoacylglycerol lipase (MAGL), a key serine hydrolase in the endocannabinoid system, in the nanomolar range. Our method could be applied to the screening of phosphotriesters, potential serine hydrolase inhibitors and signaling molecules., (© The Author(s) 2022. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

A new sarasinoside congener (sarasinoside M 2 ) and known sarasinoside B 1 were obtained from a marine sponge. Sarasinoside M 2 was suggested to have the same aglycon as sarasinoside M although the internal glucose in its sugar moiety is replaced by xylose. Sarasinosides B 1 and M 2 showed moderate cytotoxicity (approximate IC 50 5-18 μM) toward Neuro-2a and HepG2 cell lines.

Taxol was originally isolated from the yew Taxus brevifolia. Because taxol inhibits the depolymerization of microtubules, the presence of a self-resistance mechanism in Taxus spp. was hypothesized. The cloning of the cDNA for alpha and beta tubulins from Taxus cuspidata and those from the human embryonic kidney cell line HEK293T revealed that the (26)Asp, (359)Arg, and (361)Leu residues in the human beta tubulin, which are important for taxol binding, were replaced with Glu, Trp, and Met in the beta tubulin of T. cuspidata, respectively. The microtubule assembly of the recombinant alpha and beta tubulins was monitored turbidimetrically, and the results clearly demonstrated that the microtubule from T. cuspidata is less sensitive to taxol than that from HEK293T cells. The Taxus microtubule composed of the wild-type alpha tubulin and the beta tubulin with the E26D mutation restored the sensitivity to taxol. We thus postulated that the mutation identified in the beta tubulin of T. cuspidata plays a role in the self-resistance of this species against taxol.