Abstract
Domoic acid is a heterocyclic amino acid and neurotoxin that is responsible for the illness known as amnesic shellfish poisoning. Previous feeding studies suggest it is formed by a condensation reaction between geranyl diphosphate and glutamate. Geranyl diphosphate is synthesized from isopentenyl pyrophosphate and dimethylallyl pyrophosphate in a reaction catalyzed by a geranyl diphosphate synthase, a member of a broader class of enzymes known as prenyltransferases. Identifying geranyl diphosphate genes in the Pseudonitzschia multiseries genome is necessary to understand the molecular control of geranyl diphosphate (and therefore domoic acid) formation. Here, bioinformatic analyses of prenyltransferases are performed to elucidate their common features. Genes encoding proteins with like features are sought in the P. multiseries genome, and those selected had their homology-modeled- proteins' catalytic pocket's depth measured to be compared with those of validated prenyltransferase crystal structures. Those with pocket size consistent with that of known geranyl diphosphate synthase were marked as likely geranyl diphosphate synthases, whereas others with larger pockets were marked as producing larger products. Two P. multiseries proteins were determined to have pocket sizes and features consistent with the formation of geranyl diphosphate. Five others were determined to form either larger products or cis-prenyltransferases.