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Biosynthetic route towards saxitoxin and shunt pathway
Shigeki Tsuchiya1, Yuko Cho1, Keiichi Konoki1
1Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiya, Aoba-ku, Sendai 981-8555, Japan.
Scientific Reports
|February 5, 2016
Summary
This study reveals the biosynthetic pathway for saxitoxin (PSTs), identifying key precursors Int-A' and Int-C'2 in cyanobacteria. It also uncovers a shunt pathway where Int-C'2 is converted to Cyclic-C' and excreted.
Area of Science:
- Marine Biology
- Biochemistry
- Microbiology
Background:
- Saxitoxin (PSTs) are potent neurotoxins produced by cyanobacteria and dinoflagellates.
- Voltage-gated sodium channel blockers, PSTs pose significant ecological and health risks.
- Recent discovery of putative PST biosynthetic genes necessitates pathway elucidation.
Purpose of the Study:
- To investigate the biosynthetic route of saxitoxin (PSTs) in cyanobacteria.
- To identify genuine precursors and intermediates in saxitoxin production.
- To elucidate a potential shunt pathway in PST biosynthesis.
Main Methods:
- Utilized (15)N-labeled intermediates for tracer experiments.
- Employed high-resolution liquid chromatography-mass spectrometry (LC/MS) for analysis.
- Studied the cyanobacterium Anabaena circinalis (TA04).
Main Results:
- Demonstrated conversion of Int-A' to Int-C'2, and Int-C'2 to C1 and C2 (PSTs).
- Observed partial conversion of Int-C'2 to Cyclic-C', which was excreted extracellularly.
- Confirmed Int-A' and Int-C'2 as genuine PST precursors.
Conclusions:
- Established the direct biosynthetic route for saxitoxin (PSTs).
- Identified Cyclic-C' as a shunt product excreted by the cells.
- Provided the first direct evidence for saxitoxin biosynthesis and a shunt pathway.
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