Table 1.

Effects of the S154A, Q215A and S154A/Q215A Mutations on the Kinetic Parameters for Decarboxylation of the Whole Substrate OMP and of the Substrate Pieces EO and Phosphite Dianion Catalyzed by Yeast OMPDC

	OMPa				EOb	EO + HPO32−c
Yeast OMPDC	kcat s−1	Km μM	kcat/Km M−1 s−1	ΔΔ G‡OMP kcal/mol	(kcat/Km)EO M−1 s−1	ΔΔG‡EO kcal/mol	(kcat/Km)EO•HPi/Kd M−2 s−1	ΔΔG‡EO•HPi kcal/mol
Wildtype	15d	1.6d	9.4 × 106		0.021e		1.2 × 104e
S154A	0.082	130	630	5.7	8.7 × 10−5	3.2	0.25	6.4
Q215A	21	50	4.2 × 105	1.8	0.011	0.4	240	2.3
S154A/Q215A	0.042	110	380	6.0	1.1 × 10−4	3.1	0.14	6.7

^aReactions in the presence of 10 mM MOPS at pH 7.1, 25 °C and I = 0.105 (NaCl). Standard deviations obtained from the nonlinear least squares fit of the initial velocity data to the Michaelis-Menten equation were: k_cat≤ 4%; K_m≤ 10%. Values of k_cat = 14 s⁻¹ and K_m = 22 μM were determined for OMPDC from Escherichia Coli.

^bReactions in the presence of 50 mM MOPS at pH 7.1, 25 °C and I = 0.15 (NaCl). Standard deviations in the values of (k_cat/K_m)_EO are estimated to be ≤ 10%.

^cReactions in the presence of 10 mM MOPS and phosphite dianion at pH 7.0, 25° C and I = 0.15 (NaCl). Standard deviations in the values of (k_cat/K_m)_EO•HPi/K_d are estimated to be ≤ 10%.

^dData from the literature (16).

^eData from the literature (9).