Synthesis and Evaluation of 3-Dehydroquinate Synthase Transition State Analogs
摘要:
Analogues have been synthesized of a six-membered, cyclic transition state likely involved in elimination of inorganic phosphate from an enzyme-bound, reactive intermediate formed during 3-dehydroquinate (DHQ) synthase catalysis. A spirocyclic carbaphosphodiester and ketocarbaphosphodiester analogue were both synthesized from quinic acid via a route where the essential spiro center was introduced by a ytterbium triflate-catalyzed aldol condensation. Spirocyclic carbaphosphodiester was a modest competitive inhibitor of DHQ synthase with an inhibition constant (K-i) of 6.7 x 10(-5) M. Enzyme-bound NADH formed during inhibition of enzyme by the spirocyclic carbaphosphodiester. Spirocyclic ketocarbaphosphodiester, even at concentrations of 0.5 mM, failed to inhibit DHQ synthase. These observations are discussed from the perspective of possible conformational constraints imposed by DHQ synthase on the reactive intermediate which undergoes elimination of inorganic phosphate relative to the ionization state of this reactive intermediate.
Synthesis and Evaluation of 3-Dehydroquinate Synthase Transition State Analogs
摘要:
Analogues have been synthesized of a six-membered, cyclic transition state likely involved in elimination of inorganic phosphate from an enzyme-bound, reactive intermediate formed during 3-dehydroquinate (DHQ) synthase catalysis. A spirocyclic carbaphosphodiester and ketocarbaphosphodiester analogue were both synthesized from quinic acid via a route where the essential spiro center was introduced by a ytterbium triflate-catalyzed aldol condensation. Spirocyclic carbaphosphodiester was a modest competitive inhibitor of DHQ synthase with an inhibition constant (K-i) of 6.7 x 10(-5) M. Enzyme-bound NADH formed during inhibition of enzyme by the spirocyclic carbaphosphodiester. Spirocyclic ketocarbaphosphodiester, even at concentrations of 0.5 mM, failed to inhibit DHQ synthase. These observations are discussed from the perspective of possible conformational constraints imposed by DHQ synthase on the reactive intermediate which undergoes elimination of inorganic phosphate relative to the ionization state of this reactive intermediate.