New insights into copper monooxygenases and peptide amidation: structure, mechanism and function

• Published in: Cellular and molecular life sciences : CMLS Vol. 57; no. 8-9; pp. 1236 - 1259
• Main Authors: Prigge, S T, Mains, R E, Eipper, B A, Amzel, L M
• Format: Journal Article
• Language: English
• Published: Switzerland Springer Nature B.V 01.08.2000; Birkhäuser Verlag
• Subjects: Amides; Amidine-Lyases - chemistry; Amidine-Lyases - genetics; Amidine-Lyases - metabolism; Amino Acid Sequence; Animals; Biosynthesis; Catalysis; Copper; Copper - metabolism; Dopamine; Dopamine beta-Hydroxylase - chemistry; Dopamine beta-Hydroxylase - genetics; Dopamine beta-Hydroxylase - metabolism; Enzymes; Hormones; Humans; Mixed Function Oxygenases - chemistry; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Molecular biology; Molecular Sequence Data; Multienzyme Complexes; Peptides; Protein Conformation; Proteins; Rats; Sequence Alignment; Sequence Homology, Amino Acid; Substrate Specificity
• ISSN: 1420-682X; 1420-9071
• DOI: 10.1007/PL00000763

Many bioactive peptides must be amidated at their carboxy terminus to exhibit full activity. Surprisingly, the amides are not generated by a transamidation reaction. Instead, the hormones are synthesized from glycine-extended intermediates that are transformed into active amidated hormones by oxidative cleavage of the glycine N-C alpha bond. In higher organisms, this reaction is catalyzed by a single bifunctional enzyme, peptidylglycine alpha-amidating monooxygenase (PAM). The PAM gene encodes one polypeptide with two enzymes that catalyze the two sequential reactions required for amidation. Peptidylglycine alpha-hydroxylating monooxygenase (PHM; EC 1.14.17.3) catalyzes the stereospecific hydroxylation of the glycine alpha-carbon of all the peptidylglycine substrates. The second enzyme, peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL; EC 4.3.2.5), generates alpha-amidated peptide product and glyoxylate. PHM contains two redox-active copper atoms that, after reduction by ascorbate, catalyze the reduction of molecular oxygen for the hydroxylation of glycine-extended substrates. The structure of the catalytic core of rat PHM at atomic resolution provides a framework for understanding the broad substrate specificity of PHM, identifying residues critical for PHM activity, and proposing mechanisms for the chemical and electron-transfer steps in catalysis. Since PHM is homologous in sequence and mechanism to dopamine beta-monooxygenase (DBM; EC 1.14.17.1), the enzyme that converts dopamine to norepinephrine during catecholamine biosynthesis, these structural and mechanistic insights are extended to DBM.