TY - JOUR
T1 - Metabolomic study of saxitoxin analogues and biosynthetic intermediates in dinoflagellates using 15 N-labelled sodium nitrate as a nitrogen source
AU - Cho, Yuko
AU - Tsuchiya, Shigeki
AU - Omura, Takuo
AU - Koike, Kazuhiko
AU - Oikawa, Hiroshi
AU - Konoki, Keiichi
AU - Oshima, Yasukatsu
AU - Yotsu-Yamashita, Mari
PY - 2019/12/1
Y1 - 2019/12/1
N2 - A stable-isotope-labelling method using 15 N-labelled sodium nitrate as a nitrogen source was developed for the toxic dinoflagellate Alexandrium catenella. The labelled saxitoxin analogues (STXs), their precursor, and the biosynthetic intermediates were analyzed by column-switching high-resolution hydrophilic interaction liquid chromatography with mass spectrometry. The low contents on Day 0, high 15 N incorporation % of Int-C’2 and Int-E’ suggested that their turn-over rates are high and that the sizes of the pool of these compounds are smaller than those of the other intermediates. The experimentally determined isotopomer distributions showed that arginine, Int-C’2, 11-hydroxy-Int-C’2, Int-E’, GTX5, GTX4, C1, and C2, each existed as a combination of three populations that consisted of the non-labelled molecules and the labelled isotopomers representing molecules newly synthesized by incorporation of 15 N assimilated from the medium with two different incorporation rates. The order of 15 N incorporation % values of the labelled populations predicted by this model largely agreed with the proposed biosynthetic route. The stable-isotope-labelling method will be useful for understanding the complex mechanism of nitrogen flux in STX-producing dinoflagellates.
AB - A stable-isotope-labelling method using 15 N-labelled sodium nitrate as a nitrogen source was developed for the toxic dinoflagellate Alexandrium catenella. The labelled saxitoxin analogues (STXs), their precursor, and the biosynthetic intermediates were analyzed by column-switching high-resolution hydrophilic interaction liquid chromatography with mass spectrometry. The low contents on Day 0, high 15 N incorporation % of Int-C’2 and Int-E’ suggested that their turn-over rates are high and that the sizes of the pool of these compounds are smaller than those of the other intermediates. The experimentally determined isotopomer distributions showed that arginine, Int-C’2, 11-hydroxy-Int-C’2, Int-E’, GTX5, GTX4, C1, and C2, each existed as a combination of three populations that consisted of the non-labelled molecules and the labelled isotopomers representing molecules newly synthesized by incorporation of 15 N assimilated from the medium with two different incorporation rates. The order of 15 N incorporation % values of the labelled populations predicted by this model largely agreed with the proposed biosynthetic route. The stable-isotope-labelling method will be useful for understanding the complex mechanism of nitrogen flux in STX-producing dinoflagellates.
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U2 - 10.1038/s41598-019-39708-y
DO - 10.1038/s41598-019-39708-y
M3 - Article
C2 - 30837523
AN - SCOPUS:85062585380
VL - 9
JO - Scientific Reports
JF - Scientific Reports
SN - 2045-2322
IS - 1
M1 - 3460
ER -