TABLE 2.

Apparent kinetic parameters for IgV-catalyzed Aβ40 hydrolysis

Reaction rates were measured following incubation of increasing Aβ40 (1-100 μM) containing a constant amount of ¹²⁵I-Aβ40 (~300,000 cpm) with IgV_L2-t2E6 (3.75 μg/ml) or IgV_L-t′ 5D3 (0.15 μg/ml). Kinetic constants were obtained from nonlinear regression fits to the Michaelis-Menten equation (r² for IgV_L2-t 2E6 and IgV_L-t′ 5D3, respectively, 0.99 and 0.98).

Catalyst	Km	kcat	kcat/Km
	M × 10−5	min−1	M−1 min−1 × 103
IgVL2-t 2E6	8.0 ± 1.2	0.3 ± 0.1	3.7 ± 0.6
IgVL-t′ 5D3	1.7 ± 0.1	1.0 ± 0.1	59.0 ± 4.5