Aminoalcohol-Induced Activation of Organophosphorus Hydrolase (OPH) towards Diisopropylfluorophosphate (DFP)

PLoS One. 2017 Jan 13;12(1):e0169937. doi: 10.1371/journal.pone.0169937. eCollection 2017.

Abstract

Aminoalcohols have been addressed as activating buffers for alkaline phosphatase. However, there is no record on the buffer activation regarding organophosphorus hydrolase (OPH). Here we reported the activating effects of aminoalcohols on OPH-catalyzed hydrolysis of diisopropylfluorophosphate (DFP), an analog molecule of G-type warfare agents. The kinetic parametors kcat, Vmax and kcat/Km in the OPH reaction were remarkably increased in the buffers (pH 8.0, 25°C) containing aminoalcohols with C2 between nitrogen (N) and oxygen (O) in their structures, including triethanolamine (TEA), diethanolamine, monoethanolamine, 1-amino-2-propanol, 2-amino-2-methyl-1-propanol, and triisopropanolamine. In contrast, much lower or no rate-enhancing effects were observed in the adding of amines, alcohols, amine/alcohol mixtures, or 3-amino-1-propanol (C3 between N and O). The 300 mM TEA further increased DFP-degrading activities of OPH mutants F132Y and L140Y, the previously reported OPH mutants with desirable activities towards DFP. However, the treatment of ethylenediaminetetraacetate (EDTA) markedly abolished the TEA-induced activation of OPH. The product fluoride effectively inhibited OPH-catalyzed hydrolysis of DFP by a linear mixed inhibition (inhibition constant Ki ~ 3.21 mM), which was partially released by TEA adding at initial or later reaction stage. The obtained results indicate the activation of OPH by aminoalcohol buffers could be attributed to the reduction of fluoride inhibition, which would be beneficial to the hydrolase-based detoxification of organophosphofluoridate.

MeSH terms

  • Amino Alcohols / pharmacology*
  • Aryldialkylphosphatase / metabolism*
  • Enzyme Activation
  • Hydrolysis
  • Isoflurophate / metabolism*
  • Kinetics
  • Sphingobacterium / enzymology*
  • Substrate Specificity

Substances

  • Amino Alcohols
  • Isoflurophate
  • Aryldialkylphosphatase

Grants and funding

This research was supported in part by National Natural Science Foundation of China (Grant nos. 31101595 and 31371893), and the Fundamental Research Funds for the Central Universities (Grant no. CCNU10A0155). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.