Inhibition equivalency factors for microcystin variants in recombinant and wild-type protein phosphatase 1 and 2A assays

Diana Garibo, Cintia Flores, Xavier Cetó, Beatriz Prieto-Simón, Manel del Valle, Josep Caixach, Jorge Diogène, Mònica Campàs

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© 2014, Springer-Verlag Berlin Heidelberg. In this work, protein phosphatase inhibition assays (PPIAs) have been used to evaluate the performance of recombinant PP1 and recombinant and wild-type PP2As. The enzymes have been compared using microcystins-LR (MC-LR) as a model cyanotoxin. Whereas PP2A<inf>Rec</inf> provides a limit of detection (LOD) of 3.1 μg/L, PP1<inf>Rec</inf> and PP2A<inf>Wild</inf> provide LODs of 0.6 and 0.5 μg/L, respectively, lower than the guideline value proposed by the World Health Organization (1 μg/L). The inhibitory potencies of seven MC variants (-LR, -RR, -dmLR, -YR, -LY, -LW and -LF) have been evaluated, resulting on 50 % inhibition coefficient (IC<inf>50</inf>) values ranging from 1.4 to 359.3 μg/L depending on the MC variant and the PP. The PPIAs have been applied to the determination of MC equivalent contents in a natural cyanobacterial bloom and an artificially contaminated sample, with multi-MC profiles. The inhibition equivalency factors (IEFs) have been applied to the individual MC quantifications determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, and the estimated MC-LR equivalent content has been compared to PPIA results. PPIAs have demonstrated to be applicable as MC screening tools for environmental applications and to protect human and animal health.
Original languageEnglish
Pages (from-to)10652-10660
JournalEnvironmental science and pollution research
Issue number18
Publication statusPublished - 1 Jan 2014


  • Inhibition equivalency factors (IEFs)
  • Liquid chromatography-tandem mass spectrometry (LC-MS/MS)
  • Microcystins (MCs)
  • Multivariate data analysis
  • Protein phosphatase 1 (PP1)
  • Protein phosphatase 2A (PP2A)
  • Protein phosphatase inhibition assay (PPIA)


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