Abstract
Graphical abstractThree minor microcystins have been isolated from a Planktothrix rubescens strain. Their structures have been elucidated by one- and two-dimensional NMR spectroscopy and high-resolution tandem mass spectrometry as the compounds [Asp3,(E)-Dhb7]MC-LY (1), [Asp3,(E)-Dhb7]MC-HtyW (2), and [Asp3,(E)-Dhb7]MC-LW (3). The amino acids found at the variable positions 2 and 4 of the microcystin core structure are in accordance with the predicted amino acid substrate activation selectivities of the non-ribosomal peptide synthetases McyA and McyB described earlier for this strain. All structural microcystin variants produced by this strain were shown to inhibit protein phosphatase 1 in the nanomolar range. Electronic supplementary materialThe online version of this article (doi:10.1007/s13659-013-0001-3) contains supplementary material, which is available to authorized users.
Highlights
Three minor microcystins have been isolated from a Planktothrix rubescens strain
Their structures have been elucidated by one- and two-dimensional NMR spectroscopy and high-resolution tandem mass spectrometry as the compounds [Asp3,(E)-Dhb7]MC-LY (1), [Asp3,(E)-Dhb7]MC-HtyW (2), and [Asp3,(E)-Dhb7]MC-LW (3)
The amino acids found at the variable positions 2 and 4 of the microcystin core structure are in accordance with the predicted amino acid substrate activation selectivities of the non-ribosomal peptide synthetases McyA and McyB described earlier for this strain
Summary
Planktothrix rubescens strain No80 was grown in laboratory culture, and the dried cell biomass was extracted using aqueous methanol. 3a, 7, Adda-NH 2, 3b 3a, NHamide, Adda-2 7, Dhb-4 2, 5, 8 7 10 9, Hty-7/9 2, 3b differences observed: While the Leu methyl group resonances were missing, an additional NH proton at very low field (10.60 ppm) as well as additional signals in the aromatic region indicated the presence of Trp and the absence of Leu. Closer examination of the TOCSY and HMBC spectra, revealed that Hty, rather than the. The 1H NMR spectrum showed similarities with the spectra of both 1 and 2: The typical NH and aromatic signals of a Trp were observed as in 2, and methyl resonances as in 1 indicated the presence of Leu. the aromatic signals of the Tyr/ Hty moiety were missing. All IC50 estimates were comparable to the inhibitory activity of MC-LR, confirming that the residues in position 2, 3, 4, and 7 of the MCs have only little influence on PP-1 inhibition potency, which is mainly due to the Adda5-Glu substructure [18,19,20,21]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
