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Interaction between substrates suggests a relationship between organophosphorus-sensitive phenylvalerate- and

Mónica Benabent1, Eugenio Vilanova1, Iris Mangas1

  • 1University "Miguel Hernandez", Institute of Bioengineering, Unit of Toxicology, Elche, Spain.

Toxicology Letters
|March 1, 2014
PubMed

Insights

Organophosphorus compounds target esterases. This study found that phenylvalerate esterase (PVase) activity in chicken brains interacts with acetylcholine-hydrolyzing activity, suggesting a shared protein component.

Area of Science:

  • Neuroscience
  • Biochemistry
  • Toxicology

Background:

  • Organophosphorus compounds (OPs) are known neurotoxins that inhibit esterases like acetylcholinesterase (AChE) and neuropathy target esterase (NTE).
  • OPs also interact with other esterases, whose biological functions remain largely unknown.
  • Chicken brain fractions exhibit three distinct phenylvalerate esterase (PVase) activities: Eα, Eβ, and Eγ.

Purpose of the Study:

  • To investigate the relationship between phenylvalerate esterase (PVase) activity and acetylcholine-hydrolyzing activity in chicken brain fractions.
  • To determine if PVase components share substrates or interact with known acetylcholine-hydrolyzing enzymes.

Main Methods:

  • Kinetically discriminating three PVase components (Eα, Eβ, Eγ) in soluble chicken brain fractions.
  • Assessing the effect of acetylthiocholine (AChE substrate) on Eα PVase activity and phenylvalerate on AChE activity.
  • Evaluating the impact of mipafox (an organophosphate) on Eβ PVase activity and its interaction with acetylthiocholine hydrolysis.

Main Results:

  • Eα PVase activity was inhibited by acetylthiocholine in a non-competitive manner, while acetylthiocholine hydrolysis was competitively inhibited by phenylvalerate.
  • Eβ PVase activity was unaffected by acetylthiocholine, but acetylthiocholine hydrolysis was competitively inhibited by phenylvalerate.
  • These interactions suggest a potential overlap in the protein targets of PVase and AChE.

Conclusions:

  • A portion of phenylvalerate esterase (PVase) activity in chicken brains may involve proteins that also hydrolyze acetylthiocholine.
  • This finding highlights a potential novel interaction relevant to organophosphorus compound toxicity mechanisms.
  • Further research is warranted to fully elucidate the functional significance of these shared esterase activities.
Keywords:
CholinesteraseMipafoxPMSFPhenylvalerate esterase

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