Journal article
Flavin Nucleotide Metabolism in Plants: MONOFUNCTIONAL ENZYMES SYNTHESIZE FAD IN PLASTIDS
The Journal of biological chemistry, Vol.283(45), pp.30890-30900
11/07/2008
Handle:
https://hdl.handle.net/2376/112354
PMCID: PMC2662166
PMID: 18713732
Abstract
FAD synthetases (EC 2.7.7.2) catalyze biosynthesis of FAD from FMN and ATP.
Monofunctional FAD synthetases are known to exist in mammals and yeast;
bifunctional enzymes also catalyzing phosphorylation of riboflavin to FMN are
known to exist in bacteria. Previously known eukaryotic enzymes with FAD
synthetase activity have no sequence similarity to prokaryotic enzymes with
riboflavin kinase and FAD synthetase activities. Proteins homologous to
bacterial bifunctional FAD synthetases, yet shorter and lacking amino acid
motifs at the C terminus, were found by bioinformatic analyses in vascular
plant genomes, suggesting that plants contain a type of FAD synthetase
previously known to exist only in prokaryotes. The
Arabidopsis
thaliana
genome encodes two of such proteins. Both proteins, which we
named AtRibF1 and AtRibF2, carry N-terminal extensions with characteristics of
organellar targeting peptides. AtRibF1 and AtRibF2 cDNAs were cloned by
reverse transcription-PCR. Only FAD synthetase activity was detected in the
recombinant enzymes produced in
Escherichia coli
. FMN and ATP
inhibited both enzymes. Kinetic parameters of AtRibF1 and AtRibF2 for the two
substrates were similar. Confocal microscopy of protoplasts transformed with
enhanced green fluorescence protein-fused proteins showed that AtRibF1 and
AtRibF2 are targeted to plastids. In agreement with subcellular localization
to plastids, Percoll-isolated chloroplasts from pea (
Pisum sativum
)
synthesized FAD from imported riboflavin. Riboflavin kinase, FMN hydrolase,
and FAD pyrophosphatase activities were detected in Percoll-isolated
chloroplasts and mitochondria from pea. We propose from these new findings a
model for subcellular distribution of enzymes that synthesize and hydrolyze
flavin nucleotides in plants.
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Details
- Title
- Flavin Nucleotide Metabolism in Plants
- Creators
- Francisco J Sandoval - Institute of Biological Chemistry and theYi Zhang - Institute of Biological Chemistry and theSanja Roje - Institute of Biological Chemistry and the
- Publication Details
- The Journal of biological chemistry, Vol.283(45), pp.30890-30900
- Academic Unit
- Biological Chemistry, Institute of
- Publisher
- American Society for Biochemistry and Molecular Biology
- Identifiers
- 99900547631501842
- Language
- English
- Resource Type
- Journal article