Peanut STS

1

Enzyme Structure Mechanism
Peanut STS
Alfalfa CHS
Highly homologous overall structures.
2
Reactions Catalyzed by CHS and STS
3
Different Cyclization in STS and CHS Hydrolysis
occurs ONLY during the Cyclization of STS
No thioesterase-like motif was found in STS. How
is the hydrolysis controlled in STS?
4
(Nucleophilic) Water Molecule at the Active
Sites of STSs
Crystal structure of stilbene synthase from
Arachis hypogaea. Shomura, Y, Torayama, I, Suh,
D-Y, Kita, A, Sankawa, U and Miki, K (2005)
Proteins 60 803
5
Proposed Aldol Switch Hydrogen Bond Network at
the STS Active Site
STS Active Site
3.0 Å
3.0 Å
2.8 Å
(3.6 Å)
2.8 Å
(3.5 Å)
2.7 Å
2.7 Å
(3.8 Å)
2.7 Å
2.7 Å
2.7 Å
putative nucleophilic water / hydroxide ion
An aldol switch discovered in stilbene synthases
mediates cyclization specificity of type III
polyketide synthases. Austin et al. Noel, JP
(2004) Chem. Biol. 111179
6
Reaction Sequence in the STS Cyclization Hydrolys
is Occurs First.
?
?
CTAA