Ethanol-inducible cytochrome P450 2E1 (CYP2E1) involved in the metabolism of gluconeogenetic precursors and some cytotoxins is distinguished from other cytochrome P450 enzymes by its rapid turnover (in vivo half-life of 4-7 h), with ligands to the haem iron, both substrates and inhibitors, stabilizing the protein. CYP2E1 is also known to have a high oxidase activity in the absence of substrate, resulting in the production of reactive oxygen radicals. We suggested that the rapid intracellular turnover of the enzyme may be partly due to covalent modifications by such radicals or to other changes during catalytic cycling, in which case the inhibition of electron supply from NADPH-cytochrome P450 reductase would be expected to stabilize the protein. Fao hepatoma cells, where CYP2E1 showed a half-life of 4 h upon serum withdrawal, were treated for 1 h with 0.3 μM diphenylene iodonium (DPI), a suicide inhibitor of flavoenzymes, which resulted in ≈ 90% inhibition of the microsomal NADPH-cytochrome P450 reductase and CYP2E1-dependent chlorzoxazone hydroxylase activities. Subsequent cycloheximide chase revealed that the CYP2E1 half-life increased to 26 h. Neither the degradation rates of total protein, CYP2B1 and NADPH-cytochrome P450 reductase nor the cellular ATP level were affected by DPI under the conditions employed. These results demonstrate for the first time that the short half-life of CYP2E1 in vivo may be largely due to the rapid destabilization of the enzyme during catalytic cycling rather than to the intrinsic instability of the protein molecule.
Skip Nav Destination
Follow us on Twitter @Biochem_Journal
Article navigation
June 1999
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
Research Article|
May 25 1999
Relationship between cytochrome P450 catalytic cycling and stability: fast degradation of ethanol-inducible cytochrome P450 2E1 (CYP2E1) in hepatoma cells is abolished by inactivation of its electron donor NADPH–cytochrome P450 reductase Available to Purchase
Andrei ZHUKOV;
Andrei ZHUKOV
1
1To whom correspondence should be addressed (e-mail [email protected]).
Search for other works by this author on:
Magnus INGELMAN-SUNDBERG
Magnus INGELMAN-SUNDBERG
1Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, S-171 77 Stockholm, Sweden
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
February 02 1999
Accepted:
March 16 1999
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1999
1999
Biochem J (1999) 340 (2): 453–458.
Article history
Received:
February 02 1999
Accepted:
March 16 1999
Citation
Andrei ZHUKOV, Magnus INGELMAN-SUNDBERG; Relationship between cytochrome P450 catalytic cycling and stability: fast degradation of ethanol-inducible cytochrome P450 2E1 (CYP2E1) in hepatoma cells is abolished by inactivation of its electron donor NADPH–cytochrome P450 reductase. Biochem J 1 June 1999; 340 (2): 453–458. doi: https://doi.org/10.1042/bj3400453
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Biochemical Society Member Sign in
Sign InSign in via your Institution
Sign in via your InstitutionGet Access To This Article
Cited By
Follow us on Twitter @Biochem_Journal
Open Access for all
We offer compliant routes for all authors from 2025. With library support, there will be no author nor reader charges in 5 journals. Check here |
![]() View past webinars > |