Linked Life Data

12355149

Source:http://linkedlifedata.com/resource/pubmed/id/12355149

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
2002-9-30
pubmed:abstractText
Isoprene (2-methyl-1,3-butadiene) is the most abundant biogenic hydrocarbon released from vegetation, and there is continuing interest in understanding its biosynthesis from photosynthetic precursors in leaf chloroplasts. We used on-line proton-transfer-reaction mass spectrometry (PTR-MS) to observe the kinetics of (13)C-labeling of isoprene following exposure to (13)CO(2) and then the loss of (13)C after a return to normal (12)CO(2) in oak ( Quercus agrifolia Nee) and cottonwood (Populus deltoides Barr.) leaves. Assignments of labeled isoprene species were verified by gas chromatography-mass spectrometry. For the first time, it was possible to observe the half-lives of individually (13)C-labeled isoprene species during these transitions, and to trace some of the label to a C3 fragment that contained the two isoprene carbons derived from pyruvate via the deoxyxylulose-5-phosphate (DOXP) pathway. At steady state (under (13)CO(2)), approximately 80% of isoprene carbon was labeled, with fully labeled isoprene as the major species (approx. 60%). The source of the unlabeled C is suggested to be extrachloroplastic, but not from photorespiratory carbon. After a transfer to (12)CO(2), (13)C-labeling persisted in one isoprene carbon for several hours; this persistence was much more pronounced in (i) leaves inhibited by fosmidomycin, a specific inhibitor of the DOXP pathway, and (ii) in sun leaves which have higher ratios of soluble sugars to starch. From the mass 41-44 fragment data, and labeling predicted from the DOXP pathway in chloroplasts, precursors may arise from cytosolic pyruvate/phospho enolpyruvate equivalents transported into the chloroplast; this idea was supported by an indirect measure of pyruvate labeling. Other sources of cytosolic isoprene precursors (i.e. dimethylallyl diphosphate or pentose phosphate) could not be excluded. The data obtained shed light on the half-lives of photosynthetic metabolites, exchanges of carbon between cellular pools, and suggest multiple origins of isoprene precursors in leaves.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0032-0935
pubmed:author
pubmed:issnType
Print
pubmed:volume
215
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
894-905
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed-meshheading:12355149-Algorithms, pubmed-meshheading:12355149-Butadienes, pubmed-meshheading:12355149-Carbon Dioxide, pubmed-meshheading:12355149-Carbon Isotopes, pubmed-meshheading:12355149-Chloroplasts, pubmed-meshheading:12355149-Cytosol, pubmed-meshheading:12355149-Fosfomycin, pubmed-meshheading:12355149-Gas Chromatography-Mass Spectrometry, pubmed-meshheading:12355149-Half-Life, pubmed-meshheading:12355149-Hemiterpenes, pubmed-meshheading:12355149-Light, pubmed-meshheading:12355149-Lovastatin, pubmed-meshheading:12355149-Models, Biological, pubmed-meshheading:12355149-Oxygen, pubmed-meshheading:12355149-Oxygen Consumption, pubmed-meshheading:12355149-Pentanes, pubmed-meshheading:12355149-Photosynthesis, pubmed-meshheading:12355149-Plant Leaves, pubmed-meshheading:12355149-Populus, pubmed-meshheading:12355149-Pyruvic Acid, pubmed-meshheading:12355149-Quercus
pubmed:year
2002
pubmed:articleTitle
On-line analysis of the (13)CO(2) labeling of leaf isoprene suggests multiple subcellular origins of isoprene precursors.
pubmed:affiliation
Institut für Ionenphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck Austria. tomkarl@ucar.edu
pubmed:publicationType
Journal Article