Table 1.

Fractional Product Yields for the Reaction of (R)-Glyceraldehyde 3-Phosphate in the Presence of K12G Mutant Yeast Triosephosphate Isomerase in D₂O.^a

[K12G TIM]	kobsd (s −1)b		MG (fMG)totc	MG (fMG)Nd	MG (fMG)Ee	d-GAP (fP)of	DHAP (fP)of	d-DHAP (fP)of
85 µM	3.6 × 10−4		0.25	0.05	0.20	0.27	0.25	0.21
		fEg			0.21	0.28	0.26	0.22
		(fE)PTh				0.35	0.33	0.28
12 µM	8.2 × 10−5		0.34	0.21	0.13	0.26	0.22	0.19
		fEg			0.16	0.33	0.28	0.24
		(fE)PTh				0.40	0.33	0.29
Average Values		fEg			0.18 ± 0.02	0.31 ± 0.03	0.27 ± 0.01	0.23 ± 0.01
		(fE)PTh				0.38 (0.21)i	0.33 (0.49)i	0.29 (0.31)i

^aProduct distributions for the reaction of GAP (10 mM) at pD 7.9 (10 mM imidazole), 25 °C and I = 0.15 (NaCl) were determined by ¹H NMR spectroscopy as described previously (32)

^bObserved first-order rate constant for disappearance of GAP in the presence of the indicated concentration of K12G TIM.

^cTotal initial fractional yield of methylglyoxal determined by extrapolation of (f_P)_obsd to zero time (intercept in Figure 1B).

^dInitial fractional initial yield of methylglyoxal from the competing nonenzymatic reaction of GAP, calculated using eq 4.

^eInitial fractional yield of methylglyoxal from the enzymatic reaction of GAP, calculated using eq 5.

^fInitial fractional product yields determined by extrapolation of (f_P)_obsd to zero time (intercepts in Figure 1B).

^gNormalized fractional yields of the products of the enzymatic reaction of GAP, calculated using eq 9.

^hNormalized fractional yields of the three products of proton transfer to the enzyme-bound enediolate intermediate, calculated using eq 10.

ⁱData for the wildtype enzyme from chicken muscle taken from previous work (32).