TABLE 3.

Biochemical characterization of IdnO and IdnD activities^a

Substrateb	Sp act (nmol/min/mg)c								Approx. Kmd
	IdnO				IdnD				IdnO	IdnD
	NAD	NADP	NADH	NADPH	NAD	NADP	NADH	NADPH
d-Gluconate	107.0	1.6	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	2 mM
d-Gluconate-6-phosphate	10.2	0.4	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
5KG	<0.01	<0.01	4,000.0	3,340.0	<0.01	<0.01	48.0	36.0	500 μM	1 mM
l-Idonate	<0.01	<0.01	<0.01	<0.01	17.4	<0.01	<0.01	<0.01		25 mM

^aE. coli DH5α cells harboring plasmid pCB95 (IdnO) or pCB96 (IdnD) were induced by the addition of 1 mM IPTG for 2 h. 

^bSubstrate concentrations of 300 mM. 

^cLower than detectable activity was measured with d-glucose, d-galactonate, d-galacturonate, d-glucuronate, d-sorbose, d-sorbitol, and 2-ketogluconate. 

^dApproximate K_m values were determined with crude cell extracts.