Table 1.

Rate Constants and Transition-State Binding Energies ΔΔG^‡ for HsAdK1-Catalyzed Phosphoryl Transfer from 1.0 mM ATP to AMP and to Phosphite Dianion.^a

Phosphoryl Acceptor	Kinetic Parameter	ΔΔG‡ (kcal/mol) b
AMP	kcat/Km (7.0 ± 0.4) x 106 M−1 s−1	≥ 14.7 c
HPO32− + EA	(kcat)HPi•EA/KHpiKEA (2.58 ± 0.05) x 102 M−2 s−1 d	≥ 8.7 e
HPO32−	(kHpi)E ≤1.0 x 10−4 M−1 s−1 f

^aAt 25 ° C and pH 7.5.

^bCalculated from the ratio of rate constants for HsAdK1-catalyzed reactions of AMP and the substrate piece (HPO₃²⁻) or pieces (HPO₃²⁻ + EA).

^cAssuming similar intrinsic nucleophilic reactivities for AMP and phosphite dianion.

^dDetermined from the fit of data from Figure 1B to eq 2.

^eCalculated from the ratio of rate constant for HsAdK1-catalyzed reactions of phosphite in the presence and absence of EA.¹⁸

^fThe slope from Figure S3B (see text).