Chlorotyrosine is a modified amino acid produced when hypochlorous acid (HOCl), generated by the enzyme myeloperoxidase (MPO) in activated neutrophils, reacts with tyrosine residues on proteins or free tyrosine. Biochemically it is classified as a halogenated amino-acid derivative and is typically quantified in plasma, serum, or urine as free or protein-bound chlorotyrosine, often reported relative to total tyrosine. The link between MPO activity and chlorinated tyrosines was established in studies of oxidative mechanisms in inflammation. Rather than acting as an active signaling molecule, chlorotyrosine serves as a durable molecular record of neutrophil-driven halogenation and protein oxidation, providing a window into specific oxidative pathways that other broad redox markers may not distinguish.

Elevated chlorotyrosine suggests increased neutrophil MPO activity and greater protein chlorination, reflecting a local or systemic environment with active halogenative oxidative stress. In cardiovascular contexts this pattern is often considered alongside oxidized lipids, inflammatory markers, and endothelial dysfunction to evaluate whether neutrophil-driven oxidation is contributing to vascular processes. Low or near-baseline chlorotyrosine levels indicate less detectable protein chlorination or lower MPO-related activity, but this can result from normal variability, timing of sample collection, clearance differences, or competing oxidative pathways. Interpretation should always be made in the context of the full Cardio Zoomer profile and clinical information rather than on chlorotyrosine alone.

Chlorotyrosine is included in Cardio Zoomer to capture MPO- and neutrophil-related halogenative stress, a distinct oxidative pathway that complements measures like F2-isoprostanes, oxidized LDL, and inflammatory cytokines. Its presence helps clinicians distinguish specific oxidative mechanisms from general inflammation, informing a more precise picture of vascular and inflammatory balance for individualized risk assessment and monitoring.