Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase.

Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Research Abstract Details 

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Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Abstract Text:

Timothy J Sontag,Robert S Parker,

Human cytochrome P450 4F2 (CYP4F2) catalyzes the initial omega-hydroxylation reaction in the metabolism of tocopherols and tocotrienols to carboxychromanols and is, to date, the only enzyme shown to metabolize vitamin E. The objective of this study was to characterize this activity, particularly the influence of key features of tocochromanol substrate structure. The influence of the number and positions of methyl groups on the chromanol ring, and of stereochemistry and saturation of the side chain, were explored using HepG2 cultures and microsomal reaction systems. Human liver microsomes and microsomes selectively expressing recombinant human CYP4F2 exhibited substrate activity patterns similar to those of HepG2 cells. Although activity was strongly associated with substrate accumulation by cells or microsomes, substantial differences in specific activities between substrates remained under conditions of similar microsomal membrane substrate concentration. Methylation at C5 of the chromanol ring was associated with markedly low activity. Tocotrienols exhibited much higher Vmax values than their tocopherol counterparts. Side chain stereochemistry had no effect on omega-hydroxylation of alpha-tocopherol (alpha-TOH) by any system. Kinetic analysis of microsomal CYP4F2 activity revealed Michaelis-Menten kinetics for alpha-TOH but allosteric cooperativity for other vitamers, especially tocotrienols. Additionally, alpha-TOH was a positive effector of omega-hydroxylation of other vitamers. These results indicate that CYP4F2-mediated tocopherol-omega-hydroxylation is a central feature underlying the different biological half-lives, and therefore biopotencies, of the tocopherols and tocotrienols.

Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Publishing Authors By Initials

TJ Sontag,RS Parker,

For similar heterocyclic compounds: heterocyclic compounds, 2-ring: benzopyrans: vitamin e research abstracts see: heterocyclic compounds: heterocyclic compounds, 2-ring: benzopyrans: vitamin e research

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Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Journal Published:

PUBLICATION TYPE: Research Support, U.S. Gov't,

Journal: Journal of lipid research

VOLUME: 48

Page Numbers: 1090-8

Journal Abbreviation:

ISSN: 0022-2275

DAY: 6

MONTH: 02

YEAR: 2007

Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 376606

Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Keywords Mesh Terms:

KEYWORDS: Vitamin E

MESH TERMS: metabolism

Chemical & Substance for Abstract: Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase. Information

Substance Name: tocopherol-omega-hydroxylase

Registry Number: EC 1.-

Grant and Affiliation Information for Influence of major structural features of tocopherols and tocotrienols on their omega-oxidation by tocopherol-omega-hydroxylase.

AFFILIATION: Division of Nutritional Sciences, Cornell University, Ithaca, NY 14850, USA.

Country: United States

AGENCY: United States NIDDK

GRANT: DK-07158-25

ACRONYM: DK

MEDLINETA: J Lipid Res

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