Table 3.

Effect of 4′-substituents on the decarboxylation reactions of the truncated substrates EO and FEO catalyzed by yeast OMPDC at 25 °C.

Substrate	4′-Substituent	Effect of 4′-Substituent	ΔΔG‡ (kcal/mol)
EO	CH2OPO32−	+ 4.2 × 108-fold a	−11.7
FEO	CH2OPO32−	+ 1.2 × 106-fold a	−8.3
EO	CH2OH	−140-fold b	+2.9
EO + HPO32−	CH2OH	−1.3 × 106-fold c	+8.3
FEO	CH3	−130-fold b	+2.9
FEO + HPO32−	CH3	−3000-fold c	+4.7

^aCalculated from the values of k_cat/K_m for the decarboxylation of OMP (1.1 × 10⁷ M⁻¹ s⁻¹, Ref. 7) and FOMP (1.2 × 10⁷ M⁻¹ s⁻¹, Ref. 27) at pH 7.1 and I = 0.105 (NaCl) and the values of (k_cat/K_m)E in Table 1 for the decarboxylation of EO and FEO at pH 7.0 and I = 0.14 (NaCl).

^bCalculated from the values of (k_cat/K_m)E in Table 1 for the unactivated decarboxylation reactions of EO, orotidine, FEO, and 5′-dFO at pH 7.0 or pH 7.1 (for orotidine) and I = 0.14 (NaCl).

^cCalculated from the values of (k_cat/K_m)_E·Hpi/K_d in Table 1 for the phosphite-activated decarboxylation reactions of EO, FEO, and 5′-dFO at pH 7.0 and I = 0.14 (NaCl) and the reaction of orotidine at pH 7.1 and I = 0.21 (NaCl).