hemecontaining

Heme-containing describes molecules that incorporate a heme prosthetic group, a iron-containing porphyrin complex essential for a wide range of biological functions. The heme group consists of a protoporphyrin IX ring coordinating a single iron atom at its center. In proteins, the iron cycling between ferrous (Fe2+) and ferric (Fe3+) states enables ligand binding, electron transfer, and catalytic activity. Both free heme (hemin) and protein-bound heme are relevant, though the term is most often used for heme as a functional cofactor in proteins.

In biology, heme-containing proteins, or hemoproteins, include hemoglobin and myoglobin for oxygen transport and storage; cytochromes such as cytochrome c for electron transfer in respiration; and enzymes like cytochrome P450 monooxygenases, catalases, and peroxidases that participate in oxidation, detoxification, and defense against reactive species. Heme also contributes to signaling and sensing processes in various organisms, where its binding state can influence regulatory pathways.

Plants, algae, and many bacteria also rely on heme-containing enzymes, while chlorophyll in plants uses a magnesium porphyrin instead of iron. Heme biosynthesis is a conserved, multi-step process typically occurring in mitochondria and cytosol, starting with the formation of delta-aminolevulinic acid and ending with insertion of iron by ferrochelatase to produce heme. Defects in this pathway can cause porphyrias, disorders characterized by abnormal porphyrin accumulation and related symptoms.

Heme-containing proteins are central to energy production, metabolism, detoxification, and signaling, making them essential across biology and medicine.