Document Detail

Dedicated roles of plastid transketolases during the early onset of isoprenoid biogenesis in pepper fruits1.
MedLine Citation:
PMID:  9701598     Owner:  NLM     Status:  MEDLINE    
Isopentenyl diphosphate (IPP), which is produced from mevalonic acid or other nonmevalonic substrates, is the universal precursor of isoprenoids in nature. Despite the presence of several isoprenoid compounds in plastids, enzymes of the mevalonate pathway leading to IPP formation have never been isolated or identified to our knowledge. We now describe the characterization of two pepper (Capsicum annuum L.) cDNAs, CapTKT1 and CapTKT2, that encode transketolases having distinct and dedicated specificities. CapTKT1 is primarily involved in plastidial pentose phosphate and glycolytic cycle integration, whereas CapTKT2 initiates the synthesis of isoprenoids in plastids via the nonmevalonic acid pathway. From pyruvate and glyceraldehyde-3-phosphate, CapTKT2 catalyzes the formation of 1-deoxy-xylulose-5-phosphate, the IPP precursor. CapTKT1 is almost constitutively expressed during the chloroplast-to-chromoplast transition, whereas CapTKT2 is overexpressed during this period, probably to furnish the IPP necessary for increased carotenoid biosynthesis. Because deoxy-xylulose phosphate is shared by the plastid pathways of isoprenoid, thiamine (vitamin B1), and pyridoxine (vitamin B6) biosynthesis, our results may explain why albino phenotypes usually occur in thiamine-deficient plants.
F Bouvier; A d'Harlingue; C Suire; R A Backhaus; B Camara
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Plant physiology     Volume:  117     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1998 Aug 
Date Detail:
Created Date:  1998-09-21     Completed Date:  1998-09-21     Revised Date:  2013-04-17    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1423-31     Citation Subset:  IM    
Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique and Université Louis Pasteur, 12 rue du Général Zimmer, 67084 Strasbourg, France.
Data Bank Information
Bank Name/Acc. No.:
GENBANK/Y15781;  Y15782
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MeSH Terms
Amino Acid Sequence
Base Sequence
Capsicum / enzymology*
DNA, Complementary
Isoenzymes / chemistry,  metabolism*
Molecular Sequence Data
Organophosphorus Compounds / metabolism
Plants, Medicinal*
Plastids / enzymology*
Polyisoprenyl Phosphates / biosynthesis*
Pyridoxine / biosynthesis
Sequence Homology, Amino Acid
Thiamine / biosynthesis
Transketolase / chemistry,  metabolism*
Reg. No./Substance:
0/DNA, Complementary; 0/Hemiterpenes; 0/Isoenzymes; 0/Organophosphorus Compounds; 0/Polyisoprenyl Phosphates; 358-71-4/isopentenyl pyrophosphate; 59-43-8/Thiamine; 65-23-6/Pyridoxine; EC

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