Matrix metalloproteinases (MMPs), also called matrixins, , are zinc-dependent endopeptidases that participate in ECM degradation. Under normal physiological conditions, the activities of MMPs are precisely regulated at the level of transcription, activation of the precursor zymogens, interaction with specific ECM components, and inhibition by endogenous inhibitors. TIMPs are specific inhibitors of Matrix metalloproteinases that participate in controlling the local activities of MMPs in tissues. MMPs are excreted by a variety of connective tissue and pro-inflammatory cells. MMPs are usually minimally expressed in normal physiological conditions and thus homeostasis is maintained. However, MMPs are regulated by hormones,growth factors, and cytokines, and are involved in ovarian functions.
MMPs play a central role in cell proliferation, migration, differentiation, angiogenesis, apoptosis and host defences. MMPs can interact with cell surface receptors and play an intriguing role in apoptosis, showing both apoptotic and anti-apoptotic action. Dysregulation of MMPs has been implicated in many diseases including arthritis, chronic ulcers, encephalomyelitis and cancer. MMPs are secreted by tumor cells themselves or by surrounding stromal cells stimulated by the nearby tumor.
The MMPs comprise a highly diverse family of enzymes, which share several common properties and domain structures. Based on their domain structure and substrate preference, they are traditionally grouped into:
Four are type I transmembrane proteins (MMP-14, MMP-15, MMP- 16, and MMP-24), and two are glycosylphosphatidylinositol (GPI) anchored proteins (MMP-17 and MMP-25).
Including MMP-12, MMP-19, MMP-20, MMP-21, MMP-23, MMP-27, and MMP-28.