Document Detail

Interference of electron transport inhibitors with desaturation of monogalactosyl diacylglycerol in intact chloroplasts.
MedLine Citation:
PMID:  2650625     Owner:  NLM     Status:  MEDLINE    
Isolated intact chloroplasts are able to desaturate fatty acids in newly synthesized monogalactosyl diacylglycerol. By analogy with other systems, this desaturation might be expected to involve electron carriers. The effects of electron transport inhibitors on chloroplast lipid-linked desaturation were therefore investigated. Because desaturation occurs in the dark and is not inhibited by compounds specifically blocking photosystem II, it appeared that the photosystems themselves did not participate. Several compounds that prevent enzymatic reoxidation of plastoquinol in thylakoid membranes at the Qz site or withdraw electrons from this lipophilic electron carrier inhibited desaturation in the dark. This inhibition could not be reversed by adding chemicals that donate electrons to photosystem I, indicating that carriers past the cytochrome b/f complex were not involved. Inhibitors of cyclic electron transport interfered with desaturation only at rather high concentrations or not at all. Additional compounds that block the reduction of quinones were slightly inhibitory. Dithioerythritol and KCN also inhibited desaturation, although their exact mode of action is unknown. Dinitrophenyl-iodonitrothymol (DNP-INT), stigmatellin, and myxothiazol did not block desaturation at concentrations that inhibited photosynthetic electron flow through the Qz site very efficiently. Therefore, these results argue against an involvement of the Qz site in desaturation. Accordingly, the inhibition by the other compounds seemingly interfering at the same site as well as that by electron acceptors could be due to interference at a different redox step in desaturation. In vitro these compounds function also as electron acceptors in diaphorase reactions catalyzed by ferredoxin:NADP oxidoreductase.
J Andrews; H Schmidt; E Heinz
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Archives of biochemistry and biophysics     Volume:  270     ISSN:  0003-9861     ISO Abbreviation:  Arch. Biochem. Biophys.     Publication Date:  1989 May 
Date Detail:
Created Date:  1989-05-24     Completed Date:  1989-05-24     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0372430     Medline TA:  Arch Biochem Biophys     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  611-22     Citation Subset:  IM    
Institut für Allgemeine Botanik, Universität Hamburg, Federal Republic of Germany.
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MeSH Terms
Chlorophyll / metabolism*
Chloroplasts / metabolism*
Chromatography, High Pressure Liquid
Diglycerides / metabolism*
Electron Transport / drug effects
Enzyme Inhibitors / pharmacology*
Fatty Acid Desaturases / antagonists & inhibitors,  metabolism*
Glycerides / metabolism*
Glycolipids / metabolism*
Light-Harvesting Protein Complexes
Oxidation-Reduction / drug effects
Photosynthetic Reaction Center Complex Proteins
Photosystem I Protein Complex
Photosystem II Protein Complex
Plant Proteins / metabolism*
Reg. No./Substance:
0/Diglycerides; 0/Enzyme Inhibitors; 0/Galactolipids; 0/Glycerides; 0/Glycolipids; 0/Light-Harvesting Protein Complexes; 0/Photosynthetic Reaction Center Complex Proteins; 0/Photosystem I Protein Complex; 0/Photosystem II Protein Complex; 0/Plant Proteins; 0/monogalactosyldiacylglycerol; 1406-65-1/Chlorophyll; EC 1.14.19.-/Fatty Acid Desaturases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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