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Published on: January 16, 2016
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Dynamic Conformational States Dictate Selectivity toward the Native Substrate in a Substrate-Permissive
Olesya Levsh1,2, Ying-Chih Chiang3, Chun Fai Tung3
1Whitehead Institute for Biomedical Research , 9 Cambridge Center, Cambridge, Massachusetts 02142, United States.
Biochemistry
|November 3, 2016
Summary
Plant enzymes like hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (HCT) avoid errors by favoring native substrates. Structural dynamics reveal how HCT distinguishes between shikimate and other molecules, preventing futile reactions.
Area of Science:
- Plant biochemistry
- Enzymology
- Structural biology
Background:
- Hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (HCT) is crucial for plant phenylpropanoid metabolism.
- HCT catalyzes the reaction between p-coumaroyl-CoA and shikimate.
- HCT exhibits broad substrate permissiveness in vitro, raising questions about specificity.
Purpose of the Study:
- To investigate the structural and dynamic mechanisms underlying HCT's substrate specificity.
- To understand how HCT avoids functional derailment by non-native substrates.
Main Methods:
- X-ray crystallography
- Molecular dynamics simulations
Main Results:
- Distinct dynamic modes of HCT were observed under native and non-native catalysis.
- Active site plasticity allows for specific electrostatic and hydrogen-bonding interactions with shikimate.
- These interactions are elicited more effectively by shikimate than by non-native substrates.
Conclusions:
- Enzyme dynamics and active site plasticity contribute to HCT's preference for its native substrate, shikimate.
- This mechanism prevents futile catalytic cycles with non-native substrates, ensuring metabolic efficiency.
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