These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A 49-kDa mini-lipoxygenase from Anabaena sp. PCC 7120 retains catalytically complete functionality.
    Author: Zheng Y, Boeglin WE, Schneider C, Brash AR.
    Journal: J Biol Chem; 2008 Feb 22; 283(8):5138-47. PubMed ID: 18070874.
    Abstract:
    Anabaena sp. PCC 7120 is one of the few prokaryotes harboring a lipoxygenase (LOX) gene. The sequence resides in an open reading frame encoding a fusion protein of a catalase-like hemoprotein with an unusually short LOX (approximately 49 kDa) at the C terminus. The recombinant mini-LOX contains a non-heme iron in the active site and is highly active with linoleic and alpha-linolenic acids (which occur naturally in Anabaena) giving the respective 9R-hydroperoxides, the mirror image of the 9S-LOX products of plants. Using stereospecifically labeled [11-(3)H]linoleic acids we show that reaction is catalyzed via a typical antarafacial relationship of initial hydrogen abstraction and oxygenation. The mini-LOX oxygenated C16/C18:2-phosphatidylcholine with 9R specificity, suggesting a "tail first" mode of fatty acid binding. Site-directed mutagenesis of an active site Ala (Ala215), typically conserved as Gly in R-LOX, revealed that substitution with Gly retained 9R specificity, whereas the larger Val substitution switched oxygenation to 13S, implying that Ala215 represents the functional equivalent of the Gly in other R-LOX. Metabolism studies using a synthetic fatty acid with extended double bond conjugation, 9E,11Z,14Z-20:3omega6, showed that the mini-LOX can control oxygenation two positions further along the fatty acid carbon chain. We conclude that the mini-LOX, despite lacking the beta-barrel domain and much additional sequence, is catalytically complete. Interestingly, animal and plant LOX, which undoubtedly share a common ancestor, are related in sequence only in the catalytic domain; it is possible that the prokaryotic LOX represents a common link and that the beta-barrel domain was then acquired independently in the animal and plant kingdoms.
    [Abstract] [Full Text] [Related] [New Search]