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(Last modification:
07. October 2009)
Plant Type III PKS:
One
Condensation Reaction
-
This
page
- A brief overview
- Links to a few photos
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Links to
other pages
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Benzalacetone
Synthases
- Raspberry (Rubus idaeus):
more...
- Rhubarb (Rheum palmatum):
more...
-
C-Methylated Flavonoids:
more...
-
Diketide
Derivatives
-
Phenylphenalenones:
more...
- Curcuminoids:
- Curcuminoid biosynthesis by two cooperating enzymes in Curcuma
longa: more...
- Curcuminoid synthase in rice:
- does not really belong here: it is actually one enzyme
with two condensations: more...
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Proposals
-
Benzylacetone:
more...
(Note:
this is different from benzalacetone
!!)
-
Quinoline alkaloids:
more...
- Psilotonin in Psilotum nudum:
more...
- 4-Hydroxycoumarins:
more...
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A brief
overview
Type
III PKS with only one condensation reaction are involved in several natural
product biosyntheses. The prototype (and simplest case) is the formation of
benzalacetone, but there are several examples that are more complex.
One of them is likely the biosynthesis of
C-methylated flavonoids: in this case the introduction of the methyl group is
probably carried out by a special condensation reaction with methylmalonyl-CoA;
presumably this requires a special enzyme (more...).
At least equally important is the biosynthesis of the compounds
shown below. It involves one condensation reaction (1)
by a type III polyketide synthase (PKS), followed by modifying and/or tailoring
reactions to form complex end products. One of the subsequent reactions should
be a second condensation, and it is an interesting question whether this can be
carried out by the same enzyme (more...),
or whether a second protein is necessary (more...).
It may be that both possibilities are realized.
Fig. 1:
Proposal for the formation of complex natural
products via diketides synthesized by type III polyketide synthases (PKS).
The red box marks the key reaction to the diketide
intermediate; the red dots indicate the carbon
atoms introduced by the condensation reaction. The orange
boxes shows the natural products. Benzalacetone
synthase (BAS) is the prototype for such reaction, carrying out only one
condensation: it is a type III PKS: more...
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Links to plant pictures
and some specific pages
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Top left: Curcumin
in Curry (Turmeric,
Curcuma longa)
tuberous rhizomes,
->
a curcuminoid synthase from rice: ->
more...
- this looks like a most unusual case: an enzyme using two different chain extenders!
-> Curcumin
biosynthesis by two cooperating enzymes in Curcuma longa ->
more...
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Top right: Gingerol
in Ginger (Zingiber officinale)
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Bottom left: Psilotinin in
Psilotum nudum:
-> more...
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Bottom right: Phenylphenalenones in
Kangaroo paw (e.g. in
Anigozanthos
manglesii),
->
a candidate in phenylphenalenone biosynthesis ->
more...
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File History:
-
07.10.2009: Update on links: proposal for
4-hydroxycoumarin biosynthesis:
more...
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24.03.2009: Update on links: Curcumin biosynthesis in Curcuma longa:
more...
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04.03.2009: Figure modified, update on links
.
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