Paralytic Shellfish Toxins (PST)-Transforming Enzymes: A Review

Abstract

Paralytic shellfish toxins (PSTs) are a group of toxins that cause paralytic shellfish poisoning through blockage of voltage-gated sodium channels. PSTs are produced by prokaryotic freshwater cyanobacteria and eukaryotic marine dinoflagellates. Proliferation of toxic algae species can lead to harmful algal blooms, during which seafood accumulate high levels of PSTs, posing a health threat to consumers. The existence of PST-transforming enzymes was first remarked due to the divergence of PST profiles and concentrations between contaminated bivalves and toxigenic organisms. Later, several enzymes involved in PST transformation, synthesis and elimination have been identified. The knowledge of PST-transforming enzymes is necessary for understanding the processes of toxin accumulation and depuration in mollusk bivalves. Furthermore, PST-transforming enzymes facilitate the obtainment of pure analogues of toxins as in natural sources they are present in a mixture. Pure compounds are of interest for the development of drug candidates and as analytical reference materials. PST-transforming enzymes can also be employed for the development of analytical tools for toxin detection. This review summarizes the PST-transforming enzymes identified so far in living organisms from bacteria to humans, with special emphasis on bivalves, cyanobacteria and dinoflagellates, and discusses enzymes’ biological functions and potential practical applications.

Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

“…The lowest elimination rate was obtained for NEO in high TAA-acclimated mussels (DT3, 0.060 d −1 ) and under combined conditions (DT4, 0.069 d −1 ), which were dramatically lower than those under the low TAA conditions such as DT1 and DT2 (0.351 d −1 and 0.322 d −1 ). Under the circumstances of high TAA conditions, some digestive enzymes may have higher potencies, accompanied by a reduction in glutathione consumption, which plays an important role in biotransformation and elimination of PSTs in vivo [ 71 , 72 , 73 , 74 ]. In the southern rock lobster Jasus edwardsii , the uptake and depuration rates of PSTs changed among analogues, resulting in a reduction of the highly potent analogues in lobster tissues [ 27 ].…”

Microcystis Sp. Co-Producing Microcystin and Saxitoxin from Songkhla Lake Basin, Thailand

“…Currently, 57 natural STX analogs have been identified [ 41 ]. The toxin divergence depends on PST-transforming enzymes between toxigenic organisms and contaminated bivalves [ 86 ]. Carbamoyl groups of the STXs are decarbamoylated, resulting in the presence of dcSTX.…”

“…Carbamoyl groups of the STXs are decarbamoylated, resulting in the presence of dcSTX. The enzymatic decarbamoylation of STX was a major presence in mussels and human metabolically active tissues [ 86 , 87 ].…”

Paralytic and Amnesic Shellfish Toxins Impacts on Seabirds, Analyses and Management

“…), they can all consume and retain toxic microalgae, incorporating and potentially transferring their toxins in the food chain [ 22 , 23 , 71 , 72 , 73 , 74 , 75 , 76 , 77 ]. With regard to ASTs and PSTs, as well as for other biotoxins, some of these vectors convert the original compounds from the microalgae to other congeners, to eliminate them and detoxify their tissues [ 18 , 35 , 78 , 79 ].…”

“…STX and its analogs are a group of natural neurotoxic alkaloids, commonly known as PSTs [ 104 ]. The PSTs can be broadly characterized as hydrophilic or hydrophobic, and can be divided into subgroups based on substituent side chains that impart a varying level of toxicity [ 79 ]. The most representative analogue of this group is STX and the relative potency of their congeners is usually expressed by taking STX toxicity as a reference, by using toxicity equivalency factors (TEFs).…”