Carboxyl-terminal amidation, a required post-translational modification for the bioactivation of many peptide hormones, entails sequential enzymatic action by peptidylglycine α- monooxygenase (PAM, EC 1.14. 17.3) and peptidylamidoglycolate lyase (PGL, EC 4.3. 2.5). We have previously demonstrated that PAM and PGL exhibit strict tandem reaction stereospecificities, with PAM producing exclusively α-hydroxyglycine moieties of absolute ...