SPECIFIC CLEAVAGE OF BETA-LPH AND ACTH BY TONIN - RELEASE OF AN OPIATE-LIKE PEPTIDE BETA-LPH (61-78)

Tonin, a rat enzyme capable of cleaving angiotensinogen, the tetradecapeptide renin substrate and angiotensin I directly to antiotensin II is also shown to cleave beta-lipotropin into beta-LPH 1-50, 1-51, 51-60, 52-60, 61-78 and 79-91, thereby selectively releasing the opiate-like segment beta-LPH 61-78. Its action on ACTH was similar, releasing ACTH 1-8, 1-7, 3-8, 3-7 and 9-39. In both situations the cleavages are of a selective tryptic-chymotryptic type at specific arginine, phenylalanine residues. Comparison of the tonin cleavage with those of trypsin, trypsin in combination with citraconylation of the lysine residues of beta-LPH is made. The data presented show that tonin does not cleave Met-enkephalin and can be used as an enzyme to study the presence of endorphin-like sequences in polypeptides. © 1979.