Mechanism of neurotensin degradation by rat brain peptidases.

Neurotensin is degraded by peptidases present in soluble and particulate (25000 x g) fractions of rat hypothalamus, thalamus, cortex and pituitary, the soluble fraction of the hypothalamus having the highest activity. High performance liquid chromatography and amino acid analysis were used to identify the degradation pathway. The main product in both fractions was [1-8]neurotensin and the corresponding C-terminal fragment [9-13]neurotensin was identified. [1-10]Neurotensin was also identified, proportionately more of this peptide being produced by the particulate rather than the soluble fraction. In the presence of dithiothreitol, [1-7]neurotensin and [1-10]neurotensin were major products particularly in the soluble fraction. These results suggest that the main sites of cleavage of neurotensin by rat brain peptidases are the Arg8-Arg9, Pro10-Tyr11 and Pro7-Arg8 bonds.