Distinct behavior of beta-endorphin and corticotropin toward leucine aminopeptidase action.

Reactions of human beta-endorphin, corticotropin and their synthetic analogs with leucine aminopeptidase have been investigated. The results confirmed previous findings that beta-endorphin is resistant to the aminopeptidase action whereas corticotropin is not. Beta-endorphin-(1-5) is completely digested by the enzyme while beta-endorphin-(1-17) is resistant. In contrast, the NH2-terminal 7 residues in corticotropin are removed readily by leucine aminopeptidase. This is confirmed by the observation that human corticotropin-(7-38) is not hydrolyzed by the enzyme. This contrasting behavior of the two hormones toward leucine aminopeptidase may be related to differences in their conformational structures.