Involvement of Endo‐Oligopeptidases A and B in the Degradation of Neurotensin by Rabbit Brain

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Abstract
Incubation of neurotensin with rabbit brain cytosol fractions resulted in a rapid loss of carboxy-terminal neurotensin immunoreactivity, whereas the amino-terminal portion of neurotensin was relatively stable to degradation. Neurotensin degradation by rabbit brain cystosol fractions was activated by dithiothreitol and inhibited by thiol blocking reagents, Zn2 +, and by monospecific antibodies against endo-oligopeptidases A and B, thus suggesting the possible involvement of these enzymes in neurotensin degradation by rabbit brain. An association of a proportion of endo-oligopeptidase B activity (proline endo-peptidase) with the membrane fraction of nervous tissue was suggested by the presence of proline endopeptidase activity on the membranes and by immunoprecipitation of the solubilized activity using antiendo-oligopeptidase B antiserum.