Does GSTP1 rs1695 reduce detoxification capacity and increase oxidative inflammatory stress?

The GSTP1 rs1695 polymorphism alters the enzyme's physical structure, modifying cellular defenses against oxidative stress and environmental toxins.

Molecular mechanisms and detoxification capacity

• The rs1695 polymorphism (an A-to-G transition causing an Ile105Val substitution) directly reshapes the hydrophobic substrate-binding (H) cavity of the enzyme, shifting substrate specificity.
• For standard small electrophilic substrates (such as CDNB), the Val105 variant exhibits a 50% to 70% reduction in conjugation activity, a higher $K_m$ (lower binding affinity), and lower overall catalytic efficiency ($k_{cat}/K_m$).
• This variant shows up to a 15-fold decrease in catalytic activity toward certain alkylating drugs like chlorambucil, while simultaneously exhibiting a seven-fold increase in catalytic efficiency for bulky polycyclic aromatic hydrocarbons (PAHs).

Oxidative and inflammatory stress pathways

• Compromised GSTP1 activity leads to the cellular accumulation of reactive oxygen species (ROS) and electrophilic toxins. This manifests as elevated oxidative biomarkers, specifically lipid peroxidation markers like malondialdehyde (MDA), TBARS, and the DNA damage marker 8-OHdG.
• Mechanistically, healthy GSTP1 acts as a negative regulator of inflammation by suppressing NF-κB activation and subsequent nuclear translocation.
• The reduced functional capacity of the Val105 variant relieves this inhibition, promoting pro-inflammatory cytokine release and increasing clinical vulnerability to airway hyperreactivity, heavy-metal-induced oxidative stress, and chronic toxin-induced inflammation.

Bottom line

• Key takeaway: The GSTP1 rs1695 polymorphism reduces standard detoxification capacity by 50% to 70% and disrupts the enzyme's ability to inhibit NF-κB, directly increasing vulnerability to lipid peroxidation, oxidative tissue damage, and chronic inflammatory stress.