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The degradation of adrenocorticotrophic hormone-(1–4) by mouse brain cytosol

1980; Elsevier BV; Volume: 203; Issue: 1 Linguagem: Inglês

10.1016/0003-9861(80)90179-4

1096-0384

Amos Neidle, M.E.A. Reith,

Neuroscience and Neuropharmacology Research

Ser-Tyr-Ser-Met, the N-terminal tetrapeptide of adrenocorticotrophic hormone, is rapidly converted to free amino acids by mouse brain cytosol. Amino acid release was greatly reduced by puromycin, bestatin, EDTA, or o-phenanthroline. In the presence of dithiothreitol, only Ser3 and Met4 were affected. This, and other data, indicated that the mechanism of breakdown consisted of sequential aminopeptidase action followed by the cleavage of the resulting Ser-Met. Two enzymes were partially purified and shown to account for adrenocorticotrophic hormone-(1–4) degradation. The first of these is an aminopeptidase, the activities of which toward the cleavage of Leu-β-naphthylamide and the release of Ser1 and Tyr2 were purified to the extent of 453-, 429-, and 426-fold, respectively. It has properties and specificity towards aminoacyl β-naphthylamides indicating that it is identical to a neutral arylamidase purified from the brains of other species. The second enzyme was purified 110-fold and is a sulfhydryl-inhibited dipeptidase of broad specificity (EC 3.4.13.2). Some of the properties of these enzymes and their action on adrenocorticotrophic hormone fragments and other peptides are reported.