Metabolic activation of acetylenes. Covalent binding of [1,2-14C]octyne to protein, DNA and haem <i>in vitro</i> and the protective effects of certain thiol compounds

White, Ian N.H.; Campbell, J.B.; Farmer, Peter B.; Bailey, E.; Nam, Nguyễn Hoài; Thang, D.C.

doi:10.1042/bj2200085

Cited by 8 publications

(3 citation statements)

References 18 publications

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“…Less information is available on triple bond oxidation, but oxidation of terminal acetylenes to carboxylic acids takes precedence over w-2 oxidation to give propargylic alcohols (Ortiz de Montellano et al, 1985;CaJacob et al, 1988;White et al, 1984a). Furthermore, epoxidation of m-9-hexadecenoic acid shows that there is no intrinsic mechanistic impediment to cytochrome P450BM-3-catalyzed epoxidation reactions (Ruettinger & Fulco, 1981).…”

Section: Discussionmentioning

confidence: 99%

Cytochrome P450BM-3 (CYP102): Regiospecificity of oxidation of .omega.-unsaturated fatty acids and mechanism-based inactivation

Shirane

Sui²,

Peterson³

et al. 1993

Biochemistry

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Cytochrome P450BM-3 preferentially oxidized fatty acids with terminal double or triple bonds to the omega-2 hydroxylated fatty acids rather than, respectively, to the epoxide or diacid metabolites. The enzyme is inactivated during catalytic turnover of long, terminally unsaturated fatty acids but not by the analogous medium-length fatty acids. Enzyme inactivation by 17-octadecynoic acid and 16-hydroxy-17-octadecynoic acid is due to alkylation of the prosthetic heme group to given an adduct tentatively identified as N-(2-oxo-3-hydroxy-17-carboxyheptadecyl)protoporphyrin IX by its chromatographic and spectroscopic properties. Catalytic turnover of 17-octadecenoic acid also results in heme modification. Fatty diacid monoethyl thioesters are introduced as a new class of irreversible inhibitors that exploit the omega-2 oxidation specificity of cytochrome P450BM-3. Catalytic oxidation of the monoethyl thioesters of dodecanedioic and hexadecanedioic acids results in enzyme inactivation and formation of the parent diacids as metabolites. Limited tryptic digestion of the enzyme after incubation with the monoethyl thioester of [14C]hexadecanedioic acid shows that the inactivating agent binds covalently to both the heme and flavin domains. This finding, and the observation that glutathione prevents inactivation of the enzyme by the monoethyl thioesters, indicate that a diffusible metabolite, probably the sulfoxide, is responsible for enzyme inactivation. The strong preference for omega-2 allylic or propargylic hydroxylation over terminal pi-bond oxidation is opposite to the usual cytochrome P450 pattern and requires that the enzyme actively suppress terminal pi-bond oxidation. The inference that the enzyme binds and sequesters the terminal carbon in a lipophilic pocket is consistent with the crystal structure of the hemoprotein domain of cytochrome P450BM-3.

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Section: Discussionmentioning

confidence: 99%

Cytochrome P450BM-3 (CYP102): Regiospecificity of oxidation of .omega.-unsaturated fatty acids and mechanism-based inactivation

Shirane

Sui²,

Peterson³

et al. 1993

Biochemistry

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show abstract

“…The inactivation and heme loss are not prevented by glutathione, as expected if the inactivating species is not a diffusible intermediate. The fact that covalent binding to the heme group is not prevented by agents such as N-acetylcysteine or glutathione was first reported in a related case for the inactivation mediated by 1-octyne (White et al 1984).…”

Section: Prosthetic Heme Alkylation By Acetylene and Monosubstituted mentioning

confidence: 96%

“…1-Octyne, a monosubstituted acetylene, was reported to inactivate hepatic cytochrome P450 with the formation of both protein and heme covalent adducts (White et al 1984). The substrate itself was oxidized in the incubation system to 1-octyne-3-one, which was readily trapped by thiol agents via a Michael addition reaction.…”

Section: Protein Modification By Disubstituted Acetylenesmentioning

confidence: 99%

Acetylenes: cytochrome P450 oxidation and mechanism-based enzyme inactivation

Montellano

2019

Drug Metabolism Reviews

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The oxidation of carbon-carbon triple bonds by cytochrome P450 produces ketene metabolites that are hydrolyzed to acetic acid derivatives or are trapped by nucleophiles. In the special case of 17αethynyl sterols, D-ring expansion and de-ethynylation have been observed as competing pathways. The oxidation of acetylenic groups is also associated with mechanism-based inactivation of cytochrome P450 enzymes. One mechanism for this inactivation is reaction of the ketene metabolite with cytochrome P450 residues essential for substrate binding or catalysis. However, in the case of monosubstituted acetylenes, inactivation can also occur by addition of the oxidized acetylenic function to a nitrogen of the heme prosthetic group. This addition reaction is not mediated by the ketene metabolite, but rather occurs during oxygen transfer to the triple bond. In some instances, a detectable intermediate is formed that is most consistent with a ketocarbene-iron heme complex. This complex can progress to the N-alkylated heme or revert back to the unmodified enzyme. The ketocarbene complex may intervene in the formation of all the N-alkyl heme adducts, but is normally too unstable to be detected.

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Gene-environmental interactions: Lessons from porphyria

Sassa

2003

Environ Health Prev Med

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The porphyrias are uncommon, complex, and fascinating metabolic conditions, caused by deficiencies in the activities of the enzymes of the heme biosynthetic pathway. Two cardinal symptoms of the porphyrias are cutaneous photosensitivity and neurologic disturbances. Molecular analysis of gene defects has shown that there are multiple and heterogeneous mutations in each porphyria. Patients with symptomatic porphyria can suffer greatly, and, in rare cases, may die. While congenital porphyrias are inherited, other forms of porphyria occur as acquired diseases. In addition, not all gene carriers of inherited porphyrias develop clinical disease and there is a significant interplay between the gene defect and acquired or environmental factors. The variable response of porphyrias to acquired factors may, likely reflect genetic polymorphisms in drug metabolism. The lessons from acute hepatic porphyria, such as acute intermittent porphyria, are very useful in clarifying the complex nature of the clinical expression of metabolic disorders.

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Metabolic activation of acetylenes. Covalent binding of [1,2-14C]octyne to protein, DNA and haem in vitro and the protective effects of certain thiol compounds

Cited by 8 publications

References 18 publications

Cytochrome P450BM-3 (CYP102): Regiospecificity of oxidation of .omega.-unsaturated fatty acids and mechanism-based inactivation

Cytochrome P450BM-3 (CYP102): Regiospecificity of oxidation of .omega.-unsaturated fatty acids and mechanism-based inactivation

Acetylenes: cytochrome P450 oxidation and mechanism-based enzyme inactivation

Gene-environmental interactions: Lessons from porphyria

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