Table 1.

Comparison of kinetic parameters of the enzymes involved in the last two steps of NAD synthesis in F. tularensis and B. anthracis

Protein, substrate	Kinetic constants		kcat/Km, s−1·M−1	Subs. pref., fold
	kcat, s−1	Km, mM
Amidation step
ftNadE*, NaMN	0.50 ± 0.02	0.20 ± 0.04	2,500	≈60†
ftNadE*, NaAD	0.25 ± 0.02	5.82 ± 1.13	43
baNadE, NaMN	0.004 ± 0.0002	1.18 ± 0.17	3	≈3,000‡
baNadE, NaAD	2.64 ± 0.06	0.29 ± 0.02	9,100
Adenylylation step
ftNadM, NaMN	0.16 ± 0.01	0.81 ± 0.27	200	≈400§
ftNadM, NMN	2.8 ± 0.1	0.034 ± 0.004	82,000
baNadD, NaMN	25.60 ± 1.2	0.04 ± 0.01	640,000	≈45,000¶
baNadD, NMN	0.014 ± 0.001	0.94 ± 0.12	15

The apparent values of K_m (mM) and k_cat (s⁻¹) of ftNadE* and baNadE enzymes for amidation of both alternative substrates, NaMN and NaAD, at saturating concentrations of ATP (2 mM) and NH₄Cl (4 mM), and of baNadD and ftNadM enzymes for adenylylation of NaMN and NMN at saturating concentration of ATP (2 mM) were determined as described in SI Appendix, SI Text. Errors represent standard deviation. Substrate preference (Subs. pref.) is expressed as a ratio of catalytic efficiencies (k_cat^app/K_m^app) for the respective alternative substrates (see SI Appendix, SI Fig. 5 for kinetic rate plots).

^†NaMN > NaAD;

^‡NaAD > NaMN;

^§NMN > NaMN;

^¶NaMN > NMN.