<p>Peptidylglycine alpha-amidating monooxygenase (PAM) is a multifunctional protein found in secretory granules. The protein contains two enzymes that act sequentially to catalyse the alpha-amidation of neuroendocrine peptides [<cite idref="PUB00002655"/>, <cite idref="PUB00003713"/>]: </p><p> <reaction>peptidylglycine + ascorbate + O<sub>2</sub> = peptidyl-(2-hydroxyglycine) + dehydroascorbate + H<sub>2</sub>O</reaction> </p><p>The product is unstable and dismutates to glyoxylate and the corresponding desglycine peptide amide. The first step of the reaction is catalysed by peptidylglycine alpha-hydroxylating monooxygenase (PHM), and is dependent on copper, ascorbate and molecular oxygen; peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) catalyses the second step of the reaction [<cite idref="PUB00003713"/>]. Sequence analysis shows the protein to be similar to dopamine-beta-monooxygenases (DBH), a class of ascorbate-dependent enzymes that requires copper as a cofactor and uses ascorbate as an electron donor. PAM and DBH share a few regions of sequence similarity, some of which contain clusters of conserved histidine residues that may be involved in copper binding.</p>