UNIQUE REACTIVE-SITE DOMAINS OF NEUROENDOCRINE ISOFORMS OF ALPHA(1)-ANTICHYMOTRYPSIN FROM BOVINE ADRENAL-MEDULLA AND PITUITARY REVEALED BY MOLECULAR-CLONING

Molecular cloning of bovine adrenal medulla (AM) and pituitary (Pit) a lpha(1)-antichymotrypsin cDNAs indicated novel isoforms of ACT. The de duced primary sequences indicated that the AM ACT and Pit ACT possess COOH-terminal reactive-site domains that are characteristic of serpins (serine protease inhibitors). Of high interest was the finding of uni que reactive sites within AM ACT and Pit ACT which are predicted to po ssess Arg as P-1 residue. Arginine as P-1 residue parallels the cleava ge specificity of neuroendocrine prohormone processing enzymes cleavin g at basic residues. Furthermore, RT-PCR indicated tissue-specific exp ression of AM and Pit ACT mRNAs. The AM and Pit isoforms of ACT may re gulate novel target proteases involved in neuroendocrine function.