TABLE 1.

Apparent kinetic parameters determined for EcDmlA on different substrates and in the presence of different divalent metal ions

The concentration of Mn²⁺ was fixed at 5 mm for all measurements. The measurements were done at 25 °C and pH 7.5 in the presence of 150 mm KCl. The rate versus substrate concentration data are presented in Fig. 6. ND, not determined.

	EcDmlA					PpTDHc
	kcat	Km(substrate)a	kcat/Km(substrate)	Km(NAD)b	kcat/Km(NAD)	kcat/Km(substrate)
	s−1	μm	m−1 s−1	μm	m−1 s−1	m−1 s−1
d-Malated	11.7 ± 0.3	96 ± 7	1 × 105	94 ± 8	1 × 105	2 × 105
3-Isopropylmalated	0.102 ± 0.003	24 ± 3	4 × 103	70 ± 3	2 × 103	1 × 104
l(+)-Tartrated	0.26 ± 0.01	567 ± 84	5 × 102	600 ± 200	5 × 102	4 × 102
d-Isocitratef	(5.4 ± 0.2) × 10−4	1300 ± 125	4 × 10−1	ND	ND	ND
d(−)-Tartratef,g	ND	≥8000	3 × 10−1	ND	ND	ND
d-Lactatef,g	ND	≥14,000	1 × 10−1	ND	ND	ND

^a Apparent K_m for the specified substrate with a fixed concentration of NAD.

^b Apparent K_m for NAD with a fixed concentration of the specified substrate.

^c Data are taken from Ref. 33.

^d For these substrate, the concentration of NAD was fixed at 500 μm for the K_m(substrate) measurements, and the concentration of substrates was fixed at 500 μm for the K_m(NAD) measurements.

^e For l(+)-tartrate, the concentration of NAD was fixed at 2 mm for the K_m(substrate) measurements, and the concentration of substrates was fixed at 5 mm for the K_m(NAD) measurements.

^f For these substrates, the concentration of NAD was fixed at 1 mm to obtain apparent k_cat/K_m(substrate).

^g Because of the high K_m(substrate), the kinetic parameters could not be obtained for these substrates, and the k_cat/K_m(substrate) values were estimated from the linear part of the Michaelis-Menten function.