The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.

Cytochrome P450 (CYP) family of redox enzymes metabolize drugs and xenobiotics in liver microsomes. Isozyme CYP2C9 is reported to be inhibited by benzbromarone (BzBr) and this phenomenon was hitherto explained by classical active-site binding. Theoretically, it was impossible to envisage the experim...

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Autores principales:	Abhinav Parashar, Sudeep Kumar Gade, Mahesh Potnuru, Nandita Madhavan, Kelath Murali Manoj
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2014
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/432548fa0e99427e94d0f25f342a6224
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spelling	oai:doaj.org-article:432548fa0e99427e94d0f25f342a62242021-11-18T08:30:06ZThe curious case of benzbromarone: insight into super-inhibition of cytochrome P450.1932-620310.1371/journal.pone.0089967https://doaj.org/article/432548fa0e99427e94d0f25f342a62242014-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/24594849/?tool=EBIhttps://doaj.org/toc/1932-6203Cytochrome P450 (CYP) family of redox enzymes metabolize drugs and xenobiotics in liver microsomes. Isozyme CYP2C9 is reported to be inhibited by benzbromarone (BzBr) and this phenomenon was hitherto explained by classical active-site binding. Theoretically, it was impossible to envisage the experimentally derived sub-nM Ki for an inhibitor, when supra-nM enzyme and 10X KM substrate concentrations were employed. We set out to find a more plausible explanation for this highly intriguing "super-inhibition" phenomenon. In silico docking of various BzBr analogs with known crystal structure of CYP2C9 did not provide any evidence in support of active-site based inhibition hypothesis. Experiments tested the effects of BzBr and nine analogs on CYPs in reconstituted systems of lab-purified proteins, complex baculosomes & crude microsomal preparations. In certain setups, BzBr and its analogs could even enhance reactions, which cannot be explained by an active site hypothesis. Generally, it was seen that Ki became smaller by orders of magnitude, upon increasing the dilution order of BzBr analogs. Also, it was seen that BzBr could also inhibit other CYP isozymes like CYP3A4, CYP2D6 and CYP2E1. Further, amphipathic derivatives of vitamins C & E (scavengers of diffusible reactive oxygen species or DROS) effectively inhibited CYP2C9 reactions in different reaction setups. Therefore, the inhibition of CYP activity by BzBr analogs (which are also surface-active redox agents) is attributed to catalytic scavenging of DROS at phospholipid interface. The current work expands the scope of interpretations of inhibitions in redox enzymes and ushers in a new cellular biochemistry paradigm that small amounts of DROS may be obligatorily required in routine redox metabolism for constructive catalytic roles.Abhinav ParasharSudeep Kumar GadeMahesh PotnuruNandita MadhavanKelath Murali ManojPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 9, Iss 3, p e89967 (2014)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Abhinav Parashar Sudeep Kumar Gade Mahesh Potnuru Nandita Madhavan Kelath Murali Manoj The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
description	Cytochrome P450 (CYP) family of redox enzymes metabolize drugs and xenobiotics in liver microsomes. Isozyme CYP2C9 is reported to be inhibited by benzbromarone (BzBr) and this phenomenon was hitherto explained by classical active-site binding. Theoretically, it was impossible to envisage the experimentally derived sub-nM Ki for an inhibitor, when supra-nM enzyme and 10X KM substrate concentrations were employed. We set out to find a more plausible explanation for this highly intriguing "super-inhibition" phenomenon. In silico docking of various BzBr analogs with known crystal structure of CYP2C9 did not provide any evidence in support of active-site based inhibition hypothesis. Experiments tested the effects of BzBr and nine analogs on CYPs in reconstituted systems of lab-purified proteins, complex baculosomes & crude microsomal preparations. In certain setups, BzBr and its analogs could even enhance reactions, which cannot be explained by an active site hypothesis. Generally, it was seen that Ki became smaller by orders of magnitude, upon increasing the dilution order of BzBr analogs. Also, it was seen that BzBr could also inhibit other CYP isozymes like CYP3A4, CYP2D6 and CYP2E1. Further, amphipathic derivatives of vitamins C & E (scavengers of diffusible reactive oxygen species or DROS) effectively inhibited CYP2C9 reactions in different reaction setups. Therefore, the inhibition of CYP activity by BzBr analogs (which are also surface-active redox agents) is attributed to catalytic scavenging of DROS at phospholipid interface. The current work expands the scope of interpretations of inhibitions in redox enzymes and ushers in a new cellular biochemistry paradigm that small amounts of DROS may be obligatorily required in routine redox metabolism for constructive catalytic roles.
format	article
author	Abhinav Parashar Sudeep Kumar Gade Mahesh Potnuru Nandita Madhavan Kelath Murali Manoj
author_facet	Abhinav Parashar Sudeep Kumar Gade Mahesh Potnuru Nandita Madhavan Kelath Murali Manoj
author_sort	Abhinav Parashar
title	The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
title_short	The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
title_full	The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
title_fullStr	The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
title_full_unstemmed	The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.
title_sort	curious case of benzbromarone: insight into super-inhibition of cytochrome p450.
publisher	Public Library of Science (PLoS)
publishDate	2014
url	https://doaj.org/article/432548fa0e99427e94d0f25f342a6224
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The curious case of benzbromarone: insight into super-inhibition of cytochrome P450.

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