Linked Life Data

11997390

Source:http://linkedlifedata.com/resource/pubmed/id/11997390

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
2002-7-8
pubmed:abstractText
Postabsorptive elimination of the various forms of vitamin E appears to play a key role in regulation of tissue tocopherol concentrations, but mechanisms of tocopherol metabolism have not been elucidated. Here we describe a pathway involving cytochrome P450-mediated omega-hydroxylation of the tocopherol phytyl side chain followed by stepwise removal of two- or three-carbon moieties, ultimately yielding the 3'-carboxychromanol metabolite that is excreted in urine. All key intermediates of gamma-tocopherol metabolism via this pathway were identified in hepatocyte cultures using gas chromatography-mass spectrometry. NADPH-dependent synthesis of the initial gamma- and alpha-tocopherol 13'-hydroxy and -carboxy metabolites was demonstrated in rat and human liver microsomes. Functional analysis of several recombinant human liver P450 enzymes revealed that tocopherol-omega-hydroxylase activity was associated only with CYP4F2, which also catalyzes omega-hydroxylation of leukotriene B(4) and arachidonic acid. Tocopherol-omega-hydroxylase exhibited similar binding affinities but markedly higher catalytic activities for gamma-tocopherol than alpha-tocopherol, suggesting a role for this pathway in the preferential physiological retention of alpha-tocopherol and elimination of gamma-tocopherol. Sesamin potently inhibited tocopherol-omega-hydroxylase activity exhibited by CYP4F2 and rat or human liver microsomes. Since dietary sesamin also results in elevated tocopherol levels in vivo, this pathway appears to represent a functionally significant means of regulating vitamin E status.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
12
pubmed:volume
277
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
25290-6
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Cytochrome P450 omega-hydroxylase pathway of tocopherol catabolism. Novel mechanism of regulation of vitamin E status.
pubmed:affiliation
Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.