TABLE 1.

Comparison of the β-lactamase TEM-1 kinetic constants for NB2001 and nitrocefin^a

Substrate	kcata (s−1)	Kma (μM)	kcat/Km (M−1 s−1)
NB2001	0.50	6.5	7.7 × 104
Nitrocefin	3.3	15	22 × 104

^aThe assay conditions for NB2001 (fixed-time assay) and nitrocefin (continuous assay) hydrolyses are described in Materials and Methods. The kinetic constants k_cat and K_m for NB2001 were determined from a progress curve analysis fit to the integrated Michaelis-Menten equation at 16 μM NB2001 and 12.5 nM TEM-1 β-lactamase.