Table 1.

Steady-State Kinetic Parameters for M. tuberculosis IPMS^a

Fixed Substrate	Variable Substrate	kcat (s−1)	Km (μM)	kcat/Km (s−1 M−1) (×10−2)
AcCoA	α—KIV	3.5 ± 0.1	12 ± 1	34000 ± 260
AcCoA	α—KV	7.0 ± 1.3	410 ± 180	5900 ± 80
AcCoA	α—KB	10.7 ± 0.4	860 ± 160	8000 ± 25
AcCoA	PY	6.1 ± 0.5	9500 ± 1680	16 ± 1
α—KIV	AcCoA	2.1 ± 0.1	136 ± 5	150 ± 9
α—KV	AcCoA	5.0 ± 0.2	279 ± 31	180 ± 20
α—KB	AcCoA	7.6 ± 0.1	57 ± 2	1300 ± 49
PY	AcCoAb	4.5 ± 0.3	74 ± 13	610 ± 120

^aAt pH 7.4 and 25°C. The following concentrations of fixed co-substrate were used: 1 mM AcCoA, 250 μM α—KIV, 4 mM α—KV, 10 mM α—KB, and 100 mM PY.

^bSaturation curves displaying apparent linear substrate inhibition were fitted to eq. 2. The K_i for α—KV at a fixed saturating concentration of AcCoA was 10.1 ± 4.4 mM, and the K_i for AcCoA in the presence of a fixed saturating concentration of pyruvate was 4.0 ± 1.3 mM.