Molecular insights into CYP19A1 mutations and their role in estrogen production.
Level 5 - mechanism / opinion, no new human data
In vitro biochemical and structural study
PubMed 40744254 · doi:10.1016/j.abb.2025.110573
What was done
The authors generated six human CYP19A1 (aromatase) missense variants (R192H, R192Q, T201M, R264C, P308F, and M364T) via site-directed mutagenesis, expressed them in Escherichia coli, and purified the resulting enzymes. They quantified protein expression levels, evaluated androgen binding using spectral binding assays, measured steady-state aromatization kinetics for testosterone and androstenedione using UPLC-mass spectrometry, and performed structural analysis.
What was found
T201M, R264C, and P308F yielded measurable expression levels between 90 and 150 nmol P450 per liter of culture, whereas R192H, R192Q, and M364T produced no detectable P450 holoenzyme. Purified variants demonstrated typical type I spectral shifts upon androgen binding. Catalytic efficiency ratios relative to wild-type were 1.1 (T201M) and 0.9 (R264C) for androstenedione, and 0.6 (T201M) and 0.8 (R264C) for testosterone. Conversely, P308F demonstrated marked reductions in catalytic efficiency (0.2 for androstenedione and 0.1 for testosterone), with decreases in both k cat and K m.
Why it matters
These findings clarify how specific missense mutations alter aromatase expression and enzymatic activity, identifying proline 308 in the I-helix as an important residue for stabilizing the catalytically active enzyme conformation.
Limits
The study is entirely in vitro using a bacterial expression system, which may not capture mammalian post-translational modifications or cellular environments. No clinical outcomes or patient phenotypes were evaluated.
Cited by
- supports Testosterone is metabolized into estrogen in the body.