The catalytic mechanism of peptidylglycine alpha-hydroxylating monooxygenase investigated by computer simulation.

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Crespo A, Marti MA, Roitberg AE, Amzel LM, Estrin DA

The catalytic mechanism of peptidylglycine alpha-hydroxylating monooxygenase investigated by computer simulation.

J Am Chem Soc. 2006 Oct 4;128(39):12817-28.

PubMed ID

17002377 [ View in PubMed

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Abstract

The molecular basis of the hydroxylation reaction of the Calpha of a C-terminal glycine catalyzed by peptidylglycine alpha-hydroxylating monooxygenase (PHM) was investigated using hybrid quantum-classical (QM-MM) computational techniques. We have identified the most reactive oxygenated species and presented new insights into the hydrogen abstraction (H-abstraction) mechanism operative in PHM. Our results suggest that O(2) binds to Cu(B) to generate Cu(B)(II)-O(2)(.-) followed by electron transfer (ET) from Cu(A) to form Cu(B)(I)-O(2)(.-). The computed potential energy profiles for the H-abstraction reaction for Cu(B)(II)-O(2)(.-), Cu(B)(I)-O(2)(.-), and [Cu(B)(II)-OOH](+) species indicate that none of these species can be responsible for abstraction. However, the latter species can spontaneously form [Cu(B)O](+2) (which consists of a two-unpaired-electrons [Cu(B)O](+) moiety ferromagnetically coupled with a radical cation located over the three Cu(B) ligands, in the quartet spin ground state) by abstracting a proton from the surrounding solvent. Both this monooxygenated species and the one obtained by reduction with ascorbate, [Cu(B)O](+), were found to be capable of carrying out the H-abstraction; however, whereas the former abstracts the hydrogen atom concertedly with almost no activation energy, the later forms an intermediate that continues the reaction by a rebinding step. We propose that the active species in H-abstraction in PHM is probably [Cu(B)O](+2) because it is formed exothermically and can concertedly abstract the substrate HA atom with the lower overall activation energy. Interestingly, this species resembles the active oxidant in cytochrome P450 enzymes, Compound I, suggesting that both PHM and cytochrome P450 enzymes may carry out substrate hydroxylation by using a similar mechanism.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Ascorbic acid	Peptidyl-glycine alpha-amidating monooxygenase	Protein	Humans	Unknown	Cofactor	Details