BICH 441 HONORS, SPRING 2006
Problem Set #3
02/16/06
Acetolactate synthase catalyzes the condensation
of two molecules of pyruvate to form acetolactate.
2 pyruvate ý acetolactate + CO2
A. Write the reaction.
B. Draw a plausible (curly arrow) reaction mechanism for the enzyme
Show the structure of the transition states.
Show the nature of all amino acid side chains
involved in the mechanism or substrate binding.
Show the involvement of a coenzyme or coenzymes
(if any are required by your mechanism)
this is an alpha-condensation reaction catalyzed by TPP.
see p557 for the reaction and p615 for the mechanism
The HETPP resonance-stabilized carbanion attacks
the >C=O C of the incoming (second) pyruvate.
deprtonation of the TPP-adduct by a suitable base eliminates acetolactate.