Hemedependent

Heme-dependent refers to proteins, enzymes, or biological processes that require heme, an iron-containing porphyrin, to function. Heme serves as a prosthetic group or cofactor that participates in redox chemistry, oxygen binding, or catalysis. The term is commonly written with a hyphen (heme-dependent), though variants without a space or different punctuation may occur in some texts.

In enzymology, many heme-dependent systems rely on heme for activity. Examples include cytochromes, which use heme to transfer electrons in respiration and photosynthesis; catalases and peroxidases, which contain heme and detoxify reactive oxygen species; and cytochrome P450 enzymes, which depend on heme to catalyze a wide range of oxidation reactions. Heme can also regulate the function of certain transcription factors that sense cellular heme status and adjust gene expression accordingly, such as Hap1 in yeast.

In biology and medicine, some organisms are described as heme-dependent because they require exogenous heme for growth or virulence. Pathogenic bacteria and fungi may possess specialized systems to acquire heme from the host, linking heme availability to infection and survival. Regulation of heme biosynthesis and uptake allows cells to adapt to fluctuating heme supplies, conserving resources when heme is scarce and maximizing use when it is abundant.

Related topics include heme biosynthesis, heme uptake and transport systems, and heme-binding proteins.