title: Further insights into brevetoxin metabolism by de novo radiolabeling.
abstract: The toxic dinoflagellate Karenia brevis, responsible for early harmful algal blooms in the Gulf of Mexico, produces many secondary metabolites, including potent neurotoxins called brevetoxins (PbTx). These compounds have been identified as toxic agents for humans, and they are also responsible for the deaths of several marine organisms. The overall biosynthesis of these highly complex metabolites has not been fully ascertained, even if there is little doubt on a polyketide origin. In addition to gaining some insights into the metabolic events involved in the biosynthesis of these compounds, feeding studies with labeled precursors helps to discriminate between the de novo biosynthesis of toxins and conversion of stored intermediates into final toxic products in the response to environmental stresses. In this context, the use of radiolabeled precursors is well suited as it allows working with the highest sensitive techniques and consequently with a minor amount of cultured dinoflagellates. We were then able to incorporate [U-¹⁴C]-acetate, the renowned precursor of the polyketide pathway, in several PbTx produced by K. brevis. The specific activities of PbTx-1, -2, -3, and -7, identified by High-Resolution Electrospray Ionization Mass Spectrometer (HRESIMS), were assessed by HPLC-UV and highly sensitive Radio-TLC counting. We demonstrated that working at close to natural concentrations of acetate is a requirement for biosynthetic studies, highlighting the importance of highly sensitive radiolabeling feeding experiments. Quantification of the specific activity of the four, targeted toxins led us to propose that PbTx-1 and PbTx-2 aldehydes originate from oxidation of the primary alcohols of PbTx-7 and PbTx-3, respectively. This approach will open the way for a better comprehension of the metabolic pathways leading to PbTx but also to a better understanding of their regulation by environmental factors.
authors.affiliation: Institut de Chimie de Nice-PCRE (Processus Chimiques et Radiochimiques dans l'Environnement), UMR 7272 CNRS, Université de Nice Sophia-Antipolis, Faculté des Sciences, Parc Valrose Nice 06108, France. kevin.calabro@unice.fr.
authors.forename: Kevin
authors.initials: K
authors.lastname: Calabro
authors.affiliation: Plateforme "Bernard Rossi"-Laboratoire TIRO (Transporteur en Imagerie Radiothérapie et Oncologie), UMR E 4320 CEA /iBEB /SBTN-CAL, Université de Nice Sophia Antipolis, Faculté de Médecine, 28 Avenue de Valombrose, Nice 06107, France. jean-marie.guigonis@unice.fr.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Guigonis
authors.affiliation: Radioecology Laboratory, International Atomic Energy Agency-Environment Laboratories, MC 98012, Monaco. J.Teyssie@iaea.org.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Teyssié
authors.affiliation: Radioecology Laboratory, International Atomic Energy Agency-Environment Laboratories, MC 98012, Monaco. F.R.Oberhaensli@iaea.org.
authors.forename: François
authors.initials: F
authors.lastname: Oberhänsli
authors.affiliation: Geoazur Laboratory, Université de Nice-Sophia-Antipolis, UMR 7329 CNRS, UR 082 IRD, Campus Azur CNRS Bât. 1, 250 rue Albert Einstein, Sophia Antipolis Valbonne 06560, France. jean-pierre.goudour@unice.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Goudour
authors.affiliation: Radioecology Laboratory, International Atomic Energy Agency-Environment Laboratories, MC 98012, Monaco. M.Warnau@iaea.org.
authors.forename: Michel
authors.initials: M
authors.lastname: Warnau
authors.affiliation: Radioecology Laboratory, International Atomic Energy Agency-Environment Laboratories, MC 98012, Monaco. M-Y.bottein@iaea.org.
authors.forename: Marie-Yasmine Dechraoui
authors.initials: MY
authors.lastname: Bottein
authors.affiliation: Institut de Chimie de Nice-PCRE (Processus Chimiques et Radiochimiques dans l'Environnement), UMR 7272 CNRS, Université de Nice Sophia-Antipolis, Faculté des Sciences, Parc Valrose Nice 06108, France. olivier.thomas@unice.fr.
authors.forename: Olivier P
authors.initials: OP
authors.lastname: Thomas
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000981:Antiprotozoal Agents / Q000494:pharmacology; D002250:Carbon Radioisotopes; D004141:Dinoflagellida / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D005431:Florida; D060851:Gulf of America; D057097:Harmful Algal Bloom; D007553:Isotope Labeling; D007700:Kinetics; D008387:Marine Toxins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D015394:Molecular Structure; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009498:Neurotoxins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D035964:Oxocins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D064210:Secondary Metabolism / Q000187:drug effects; D015222:Sodium Channels / Q000378:metabolism; D000095702:Polyether Toxins
chemical_list: D019342:Acetic Acid; D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D002250:Carbon Radioisotopes; D008387:Marine Toxins; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D035964:Oxocins; D015222:Sodium Channels; C546611:brevetoxin 2; D000095702:Polyether Toxins; C546612:brevetoxin 3; C000594558:brevetoxin 7; C072089:brevetoxin receptor; C053342:brevetoxin