Hemopexin/matrixin, conserved site <p>Hemopexin (<db_xref db="EC" dbkey="3.2.1.35"/>) is a serum glycoprotein that binds haem and transports it to the liver for breakdown and iron recovery, after which the free hemopexin returns to the circulation [<cite idref="PUB00013985"/>]. Hemopexin prevents haem-mediated oxidative stress. Structurally hemopexin consists of two similar halves of approximately two hundred amino acid residues connected by a histidine-rich hinge region. Each half is itself formed by the repetition of a basic unit of some 35 to 45 residues. Hemopexin-like domains have been found in two other types of proteins, vitronectin [<cite idref="PUB00013984"/>], a cell adhesion and spreading factor found in plasma and tissues, and matrixins MMP-1, MMP-2, MMP-3, MMP-9, MMP-10, MMP-11, MMP-12, MMP-14, MMP-15 and MMP-16, members of the matrix metalloproteinase family that cleave extracellular matrix constituents [<cite idref="PUB00013983"/>]. These zinc endopeptidases, which belong to MEROPS peptidase subfamily M10A, have a single hemopexin-like domain in their C-terminal section. It is suggested that the hemopexin domain facilitates binding to a variety of molecules and proteins, for example the HX repeats of some matrixins bind tissue inhibitor of metallopeptidases (TIMPs).</p><p>This entry represents a conserved sequence region located at the beginning of the second repeat in the hemopexin domain.</p>