Kinetic solvent isotope effect in steady-state turnover by CYP19A1 suggests involvement of Compound 1 for both hydroxylation and aromatization steps

FEBS Lett. 2014 Aug 25;588(17):3117-22. doi: 10.1016/j.febslet.2014.06.050. Epub 2014 Jul 2.


CYP19A1, or human aromatase catalyzes the conversion of androgens to estrogens in a three-step reaction through the formation of 19-hydroxy and 19-aldehyde intermediates. While the first two steps of hydroxylation are thought to proceed through a high-valent iron-oxo species, controversy exists surrounding the identity of the reaction intermediate that catalyzes the lyase and aromatization reaction. We investigated the kinetic isotope effect on the steady-state turnover of Nanodisc-incorporated human CYP19A1 to explore the mechanisms of this reaction. Our experiments reveal a significant (∼ 2.5) kinetic solvent isotope effect for the C10-C19 lyase reaction, similar to that of the first two hydroxylation steps (2.7 and 1.2). These data implicate the involvement of Compound 1 as a reactive intermediate in the final aromatization step of CYP19A1.

Keywords: CYP19A1; C–C lyase; Human aromatase; KSIE; Steady-state kinetics.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aromatase / chemistry*
  • Aromatase / metabolism*
  • Humans
  • Hydroxylation
  • Kinetics
  • NADP / metabolism
  • Oxidation-Reduction
  • Oxygen / chemistry
  • Solvents / chemistry*
  • Water / chemistry


  • Solvents
  • Water
  • NADP
  • Aromatase
  • CYP19A1 protein, human
  • Oxygen