TABLE 1.

Kinetic constants for recombinant mouse GCLC and GCL holoenzyme

Activity assays were performed on eluted recombinant proteins, using a modification of the NADH recycling assay (14). Kinetic parameters were estimated using Lineweaver-Burk fits for the initial rate of NADH consumption at varying concentrations of glutamate. The average (±S.D.) is reported for three to six experiments. Determinations of GSH inhibition represent the mean of two experiments.

Construct	Vmaxa	Km Glu	Ki GSH
		mm	mm
GCLC	3.1 (0.38)	2.2 (0.75)	0.23
Holoenzyme	7.5 (1.1)	0.86 (0.23)	1.3

^a Micromoles of γ-GC produced per milligram of GCLC per minute.