| Role of structure and pH in cyclization of allene oxide fatty acids: implications for the reaction mechanism. | |
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MedLine Citation:
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PMID: 12426078 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Incubations of allene oxide synthases of flax or maize with the E,E-isomers of the 13- and 9-hydroperoxides of linoleic acid (E,E-13- and E,E-9-HPOD, respectively) at pH 7.5 afforded substantial yields of trans-disubstituted cyclopentenones. Under the conditions used, (Z,E)-HPODs were converted mainly into alpha-ketols and afforded only trace amount of cyclopentenones. These findings indicated that changing the double bond geometry from Z to E dramatically increased the rate of formation of the pericyclic pentadienyl cation intermediate necessary for electrocyclization of 18:2-allene oxides and thus the yield of cyclopentenones. The well-known cyclization of the homoallylic allene oxide (12,13-EOT) derived from alpha-linolenic acid 13-hydroperoxide (E,Z-13-HPOT) into cis-12-oxo-10,15-phytodienoic acid was suppressed at pH below neutral and was not observable at pH 4.5. In contrast, cyclization of the allene oxide ((9E)-12,13-EOD) derived from (E,E)-13-HPOD was slightly favoured at low pH. The finding that the cyclizations of 12,13-EOT and (9E)-12,13-EOD were differently affected by changes in pH suggested that the mechanisms of cyclization of these allene oxides are distinct. |
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Authors:
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Alexander N Grechkin; Ivan R Chechetkin; Lucia S Mukhtarova; Mats Hamberg |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Chemistry and physics of lipids Volume: 120 ISSN: 0009-3084 ISO Abbreviation: Chem. Phys. Lipids Publication Date: 2002 Dec |
Date Detail:
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Created Date: 2002-11-11 Completed Date: 2003-11-04 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0067206 Medline TA: Chem Phys Lipids Country: Ireland |
Other Details:
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Languages: eng Pagination: 87-99 Citation Subset: IM |
Affiliation:
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Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, 420503, Kazan, Russia. grechkin@mail.knc.ru |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Cyclization Cyclopentanes / chemistry, metabolism Fatty Acids / metabolism* Flax / enzymology Hydrogen-Ion Concentration Intramolecular Oxidoreductases / metabolism* Linoleic Acid / metabolism Molecular Structure Peroxides Stereoisomerism Zea mays / enzymology |
| Chemical | |
Reg. No./Substance:
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0/Cyclopentanes; 0/Fatty Acids; 0/Peroxides; 2197-37-7/Linoleic Acid; 930-30-3/cyclopentenone; EC 5.3.-/Intramolecular Oxidoreductases; EC 5.3.99.6/hydroperoxide isomerase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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