Biosynthesis of the neurotoxin domoic acid in a bloom-forming diatom

Abstract

Oceanic harmful algal blooms of Pseudo-nitzschia diatoms produce the potent mammalian neurotoxin domoic acid (DA). Despite decades of research, the molecular basis for its biosynthesis is not known. By using growth conditions known to induce DA production in Pseudo-nitzschia multiseries, we implemented transcriptome sequencing in order to identify DA biosynthesis genes that colocalize in a genomic four-gene cluster. We biochemically investigated the recombinant DA biosynthetic enzymes and linked their mechanisms to the construction of DA’s diagnostic pyrrolidine skeleton, establishing a model for DA biosynthesis. Knowledge of the genetic basis for toxin production provides an orthogonal approach to bloom monitoring and enables study of environmental factors that drive oceanic DA production.

Scalable Biosynthesis of the Seaweed Neurochemical, Kainic Acid

“…[18,21,22] The kab gene clustering is consistent with early examples of red algae clustering genes. Many organisms,i ncluding bacteria, fungi, plants,and unicellular algae,are known to cluster genes from the same biosynthetic pathway.…”

“…By scaling up the GfKabC reaction, we could isolate this product in sufficient yield to characterize it by NMR spectroscopy,which identified this product as kainic acid lactone ( Figure 2B). While the biochemical basis for this differential product distribution is an ongoing focus of study,w e suggest achemical mechanism analogous to that proposed for DabC [18] that diverges following pyrrolidine ring formation to rationalize the observed chemotype (Supporting Information, Figure S9). In contrast to the agonistic activity of kainic acid, kainic acid lactone has been shown to be an iGluR antagonist.…”

“…[14] These syntheses employ diverse methods to produce the kainoid ring pharmacophore such as ring opening followed by cyclization, [15] ene-cyclization, [16] or radical formation. [18] Thes tructural similarity between domoic acid and kainic acid allowed us to propose aconserved route of biosynthesis ( Figure 2B). [18] Thes tructural similarity between domoic acid and kainic acid allowed us to propose aconserved route of biosynthesis ( Figure 2B).…”

“…We next explored the substrate selectivity of DsKabA. The proposed A) domoic acid [18] and B) kainic acid biosynthetic pathways. In contrast, when we replaced DMAPP with GPP (geranyl pyrophosphate) in the l-glutamate reaction, we clearly Figure 2.…”

“…In contrast, when we replaced DMAPP with GPP (geranyl pyrophosphate) in the l-glutamate reaction, we clearly Figure 2. [18] To support the physiological relevance of prekainic acid in the biosynthesis of kainic acid, we examined the aqueous extract of D. simplex. The kainic acid biosynthesis (kab)g ene cluster from C) D. simplex and D) P. palmata.…”