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. 1980 Mar;77(3):1240–1244. doi: 10.1073/pnas.77.3.1240

Chemical mechanisms for cytochrome P-450 hydroxylation: evidence for acylation of heme-bound dioxygen.

S G Sligar, K A Kennedy, D C Pearson
PMCID: PMC348467  PMID: 6929480

Abstract

Using isotopic tracer methods, we have shown that dihydrolipoic acid (2,3-thioctic acid) acylates the distal oxygen of ferrous oxygenated Pseudomonas cytochrome P-450, forming a transient acyl peroxide intermediate that facilitates oxygen-oxygen bond cleavage. Single-turnover studies with 18O2 indicate one oxygen-18 atom incorporated into the carboxylate group of lipoic acid for each oxygen-18 inserted into the substrate, camphor, forming the product, exo-5-hydroxycamphor. Such a branching ratio for label indicates that water is initially released from an unlageled position and illustrates that the general P-450 mixed-function oxidase stoichiometry generates H218O from 18O2 only after multiple-turnover equilibration with the acylating carboxylate oxygen. Formation of an acyl peroxide state is a natural intermediate in peracid, "oxene", or radical mechanisms for methylene carbone oxygenation.

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Selected References

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