Heme (iron–protoporphyrin IX complex) (None universally standardized; commonly referred to as "heme" (note: no authoritative single-letter or standard short-form abbreviation))

Heme is a coordination complex of iron and protoporphyrin IX, essential as a prosthetic group in a variety of hemoproteins including hemoglobin, myoglobin, cytochromes, catalases, and peroxidases. It acts as a carrier for oxygen and electrons, enables redox catalysis, and serves as a chemical sensor in biological signal transduction pathways. Free and protein-bound heme is tightly regulated because unbound heme contributes to oxidative cellular damage and inflammation. Diseases of heme metabolism have widespread systemic effects, often impacting blood, liver, brain, and immune system function. “Heme/iron complex” is not a discrete therapeutic target but is critical for the function of many clinically relevant proteins and enzymes.

Other names

HemeHaem (British spelling)Iron–protoporphyrin IXFerroprotoporphyrin IXHemin (oxidized form)Hematin (hydroxy/ferric form)Iron–porphyrin complex

Direct binding to heme prosthetic group (e.g., antimalarial drugs, some enzyme inhibitors) - Chelation or sequestration of iron within heme (iron chelators) - Allosteric modulation of heme-protein interaction (rare, but possible for some effectors) - Enzyme inhibition or activation via heme binding, redox state manipulation, or modification of heme-dependent proteins - Scavenging of extracellular heme (e.g., haptoglobin/hemopexin therapies in development)