Chapter 8 Inactivation of neuropeptides

This chapter discusses inactivation of neuropeptides. Neuropeptides are biologically potent molecules of 2-40 amino acids, with physiological activity ranging from their acting as neurotransmitters, local hormones or, more generally, as neuromodulators. The number of identified neuropeptides in the mammalian nervous system is now over 50, and new potential members of the neuropeptide family are being described and evaluated continuously. Neuropeptides fulfill their physiological role acting in the extracellular space transmitting chemical messages by binding to specific receptors on the cell surface. Because of their crucial role in neuronal information processing, the regulation of the activity of neuropeptides is of utmost importance. It is believed that neuropeptide inactivation is carried out by peptidases anchored to the cell membrane, with their active sites facing the extracellular space. Such enzymes have been termed “ectoenzymes.” According to this assumption, an enzyme can be classified as a neuropeptidase in vivo if it can be shown that it fulfills the requirements of being an ectoenzyme, it is co-localized with its presumed target and it is capable of degrading relevant peptides.