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Regulatory mechanism of product specificity of FPP synthase
providing GPP as the specific product in Lithospermum
erythrorhizon
Miyawaki, Tatsuya
Sustainable humanosphere : bulletin of Research Institute for
Sustainable Humanosphere Kyoto University (2008), 4: 44-44
2008-09-01
http://hdl.handle.net/2433/182098
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Type
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Departmental Bulletin Paper
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Kyoto University
ABSIRACISaV[ASIIER'IIHESISFORGRADUATESCHooLOFAGRICULTURE)
Regulatory mechanism of product specificity of FPP synthase providing GPP as the
specific product in Lithospermum erythrorhizon
!t M k
Laborato7v ofPlant Gene Expression, RISH, Kyoto University
Terpenoids occur in all organisms characterized so far. In particular, plants produce a large
variety of terpenoid compounds, which are classified into hemi-, mono-, sesqui-, di-, tri- and
tetraterpenoids according to the number of carbons in the molecules that correspond C5, CIO, C15, C20,
C30 and C40 (carotenoid) compounds. Among them, monoterpenoids consist ofmajor flavor components
in plants. These C1O compounds are biosynthesized in plastids from geranyl diphosphate (GPP) provided in
vivo by GPP synthase (GPPS), whereas there is only one exception of cytosol-localized GPPS that is
reported in Lithospermum erythrorhizon, a boraginaceous plant. In order to clarify what kind of
polypeptide is responsible for the production of GPP in cytosol and what is the regulatory mechanism of
the chain elongation, we systematically cloned putative prenyl diphosphate synthases from the EST library
ofL. eiythrorhizon.
Figure shows the subcellular localization of known prenyl diphosphate synthases, either in plastid or in
cytosol. There are two types of GPP synthases, one is that fUnctioning as a homodimer and the other is
active as a heterodimer (shown in pink), while FPP synthase is cytosol-localized and fimctioning as a
homodimer. The cytosol GPPS ofL. ei ythrorhizon is presumed to be either a mutated FPPS having product
specificity for GPP or a hetoromer FPPS with an unlmown regulatory subunit. Both possibilities have been
examined with cell-free extract ofcultured L. erythrorhizon cells,
Cytesoi
FPP$
mcrdel'X
Plastid
EgeP
m'
BMAPP
GppS
GPP
fmutNnt FPPS
medel2
GGPI,S
"'
il/r{,':1 ,i'/!}•
IPP
cat
DMAPP
GFP
t ui "ky. ts ..
hetera FPPS
Figure. Two hypothesis ofcytosol-localized GPPS
44