ISSN:
1420-9071
Keywords:
Key words. Amidation; copper; peptidylglycine α-amidating monooxygenase; dopamine β-monooxygenase; electron transfer; structure; ascorbate; peptide hormones; oxygen chemistry.
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract. 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-Cα bond. In higher organisms, this reaction is catalyzed by a single bifunctional enzyme, peptidylglycine α-amidating monooxygenase (PAM). The PAM gene encodes one polypeptide with two enzymes that catalyze the two sequential reactions required for amidation. Peptidylglycine α-hydroxylating monooxygenase (PHM; EC 1.14.17.3) catalyzes the stereospecific hydroxylation of the glycine α-carbon of all the peptidylglycine substrates. The second enzyme, peptidyl-α-hydroxyglycine α-amidating lyase (PAL; EC 4.3.2.5), generates α-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 β-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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/PL00000763
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