Fig. 3.

Apparent kinetic parameters and bi-substrate kinetic analysis of LpxK. (A) A. aeolicus LpxK was assayed at a fixed 50 µM concentration of DSMP and varied amounts of ATP/Mg²⁺ ranging from 0.3 to 10 mM. The apparent K_M for ATP/Mg²⁺ was determined to be 1.6 ± 0.2 mM with a k_cat of 12.3 ± 0.4 sec⁻¹. (B) The concentration of ATP and Mg²⁺ in the assay was fixed at 5 mM while the concentration of DSMP was varied between 1.56 and 100 µM. The apparent K_M for DSMP was determined to be 7.0 ± 0.3 µM with a k_cat of 9.2 ± 0.1 sec⁻¹. (C) In this series of assays, the concentration of ATP/Mg²⁺ was varied between 0.3 and 10 mM for four fixed concentrations of the DSMP substrate (2.5, 5, 15 and 50 µM). The data was fit by a non-linear least-squares method to a sequential mechanism.