Alpha amidating enzyme
Dopamine β-monooxygenase shares many conserved disulfide bonds and contains histidine and methionine residues that may bind to copper in a similar manner.Based on sequence similarity, two additional potential family members, monooxygenase X and dopamine-β-hydroxylase-L, have been identified; their substrate specificity has not been determined. However, of the amino acid residues that are conserved among species, site-directed mutagenesis has identified a subset that are candidates for involvement in maintaining the structure of PAL and additional residues that are candidates for involvement in the PAL catalytic mechanism.Each approximately 150-amino acid domain contains a single copper binding site. The two domains are held together by a single hydrophilic linker strand, whereas the interiors of the domains are very hydrophobic.All of the histidine and methionine residues involved in coordinating the two catalytic copper ions are conserved in all known PHM sequences.
Peptidyl glycine alpha-amidating monooxygenase (PAM) catalyzes a two-step reaction resulting in the C-terminal amidation of peptides, a process important for their stability and biological activity.Conclusion: PAM-dependent amidation has the potential to signal oxygen levels in the same range as the hypoxia-inducible factor (HIF) system.Significance: Physiological effects of hypoxia may be PAM-dependent.Unlike the copper ions in the PHM reaction, which cycle from Cu during each reaction cycle, transferring reducing equivalents to molecular oxygen, the catalytic zinc presumably interacts directly with the α-hydroxylated substrate.PAL remains unique, with no close homologues identified in database screens.