The TRH-degrading ectoenzyme: a putative signal-terminator within the central nervous system and adenohypophyseal regulator of hormone secretion

The extracellular inactivation of TRH signals is catalyzed by specific TRH-degrading enzymes. The analysis of the primary structure of the TRH-degrading ectoenzyme reveals that it belongs to the family of Zndependent metallopeptidases. The tissue-specific regulation of the adenohypophyseal enzyme by peripheral hormones suggests that it may serve integrative functions within endocrine regulatory systems. In the brain, the high activity and the exclusive localization on neurons imply that this peptidase might also act as a terminator of neurotrophic TRH signals.