Table 1.

Experimental and Computed activation parameters for the systems studied here.

	Experimental Valuesa			Calculated Values
				Classical		Quantum-Corrected
Enzyme	kH (s-1)	ΔG‡	ΔΔG‡b	ΔG‡	ΔΔG‡	ΔG‡	ΔΔG‡
Wt	220	14.2	0.0	17.8	0	15.5	0.0
G121V	1.4	17.2	3.0	20.2	2.4	18.1	2.6
M42W	5.6	16.4	2.2	19.8	2.0	17.8	2.3
G121V-M42W	0.030	19.5	5.3	21.7	3.9	19.4	3.9

^aExperimental rates are from ref. 10 and corresponding activation energies were calculated with the Eyring equation. We note that ref. 43 demonstrated that the pH-independent rate for the wt is 950 s^-1, which may be more relevant to our calculations. Unfortunately, pH independent rates are not available for the mutants, but the effect of the mutations on the rates from ref. 10 is expected to be pH-independent, even if the absolute rates are not pH-independent. All free energies are in kcal/mol.

^bΔΔG^‡ is the difference in free energy barrier vs. the wild-type.