This reaction requires copper, molecular oxygen, and ascorbate.
In the second step of the reaction, peptidyl-α-hydroxyglycine α-amidating lyase (PAL; EC 22.214.171.124) catalyzes an N-dealkylation reaction, generating amidated product and glyoxylate.
In snails, both catalytic functions are encoded in the same gene, but there are four copies of the PHM domain, each with a similar dependence on copper and ascorbate but a unique peptide substrate specificity.
The catalytic core of PHM was defined using controlled protease digestion, and its structure was explored by assigning disulfides, examining site-directed mutants, and employing spectroscopy and X-ray crystallography.
Kinetic and mutagenesis studies, have provided notable insights into the architecture and function of PHM.
Interestingly, all the spectral and crystallography data indicate that the two copper ions are farther apart than expected for a reaction requiring both copper ions to undergo a reduction–oxidation cycle.In LDCVs, the same prohormone convertases that cleave propeptide precursors also cleave the PAM precursor, producing soluble PHM, soluble and membrane-anchored PAL, and soluble bifunctional PAM.