122873-90-9Relevant articles and documents
Evidence for an Intramolecular, Stepwise Reaction Pathway for PEP Phosphomutase Catalyzed P-C Bond Formation
McQueney, Michael S.,Lee, Sheng-lian,Swartz, William H.,Ammon, Herman L.,Mariano, Patrick S.,Dunaway-Mariano, Debra
, p. 7121 - 7130 (2007/10/02)
The Tetrahymena pyriformis enzyme, phosphoenolpyruvate phosphomutase, catalyzes the rearrangement of phosphoenolpyruvate to the P-C bond containing metabolite, phosphonopyruvate.To distinguish between an intra- and intermolecular reaction pathway for this process an equimolar mixture of 18O,C(2)-18O>thiophosphonopyruvate and (all 16O) thiophosphonopyruvate was reacted with the phosphonomutase, and the resulting products were analyzed by 31P NMR.The absence of the cross-over product 18O>thiophosphonoenolpyruvate in the product mixture was interpreted as evidence for an intramolecular reaction pathway.To distinguish between a concerted and stepwise intramolecular reaction pathway the pure enantiomers of the chiral substrate 18O>-thiophosphonopyruvate were prepared and the stereochemicalb course of their conversion to chiral 18O>thiophosphoenolpyruvate was determined.The assignments of the phosphorous configurations in the 18O>thiophosphonopyruvate enantiomers reported earlier (McQueney, M.S.; Lee, S.-l.; Bowman, E.; Mariano, P.S.; Dunaway- Mariano, D.J.Am.Chem.Soc. 1989, 111, 6885-6887) were revised according to the finding that introduction of the 18O label into the thiophosphonopyruvate precursor occurs with retention rather than with (the previously assumed) inversion of configuration.On the basis the observed conversion of (Sp)-18O>thiophosphonopyruvate to (Sp)-18O>thiophosphonoenolpyruvate and (Rp)-18O>thiophosphonopyruvate to (Rp)-18O>thiophosphonoenolpyruvate, it was concluded that the PEP phosphomutase reaction proceeds with retention of the phosphorus configuration and therefore by a stepwise mechanism.Lastly, the similar reactivity of the oxo- and thio-substituted phosphonopyruvate substrates (i.e., nearly equal Vmax) was interpreted to suggest that nucleophilic addition to the phosphorus atom is not rate limiting among the reaction steps.
