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Estrogen esters as substrates for human paraoxonases.

John F Teiber1, Scott S Billecke, Bert N La Du

  • 1Department of Internal Medicine, Division of Epidemiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.

Archives of Biochemistry and Biophysics
|April 7, 2007
PubMed
Summary

Mammalian paraoxonases (PONs) can hydrolyze estrogen esters, particularly diesters at the A-ring. This finding suggests new potential natural substrates for these important esterases.

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Area of Science:

  • Biochemistry
  • Enzymology
  • Molecular Biology

Background:

  • Mammalian paraoxonases (PONs 1, 2, and 3) are conserved esterases with poorly understood physiological roles and natural substrates.
  • Estrogen esters are a class of compounds whose interaction with PONs has not been previously investigated.

Purpose of the Study:

  • To characterize the hydrolysis of estrogen esters by purified recombinant human PONs (1, 2, and 3).
  • To investigate the substrate specificity of PONs towards different estrogen ester configurations.

Main Methods:

  • Purification of recombinant human PONs (1, 2, and 3).
  • Enzymatic assays to measure the hydrolysis of various estrogen mono- and diesters.
  • Comparison with the activity of human serum butyryl cholinesterase.

Main Results:

  • PONs efficiently hydrolyzed estrogen mono- and diesters at position 3 of the steroid A-ring.
  • Diesters were superior substrates compared to mono-esters, with PON3 showing particularly high activity.
  • Hydrolysis at position 17 was limited, requiring an adjacent double bond; human serum butyryl cholinesterase showed a preference for mono-esters.

Conclusions:

  • The ability of PONs to hydrolyze estrogen esters provides insights into their active site structure.
  • This study suggests that natural compounds containing aromatic ester groups may be relevant substrates for mammalian paraoxonases.