Table 3.

Kinetic parameters of GlcNAc-lipid synthases in membrane fractions from various bacterial strains

Membrane fractions from the indicated bacterial strains were assayed for the formation of [³H]GlcNAc-lipids in the presence of increasing amounts of Und-P, added as a dispersion in 1% CHAPS. Apparent kinetic parameters for Und-P were calculated from Michaelis-Menten plots (supplemental Fig. S5) using the linear regression algorithm in Sigma Plot version 12 (Systat Software, Inc. San Jose, CA). R² values were 0.9953 for GAS GacI expressed in E. coli; 0.983 for GAS GacI co-expressed with GacJ in E. coli, 0.9976 for GacI in MGAS5005, and 0.931 for GacO in MGAS5005. The results are representative of at least two separate experiments. ND = not detected.

Enzyme source	GlcNAc-P-Und		GlcNAc-P-P-Und
	Km	Vmax	Km	Vmax
	μm	pmol/min/mg	μm	pmol/min/mg
MGAS5005	6.4	333	ND	ND
5005ΔgacI	ND	ND	19.3	2.75
E. coli:GacI	18.7	54.2	ND	ND
E. coli:GacI/J	1.1	18,500	ND	ND