TABLE 2.
Kinetic constants for rat CCTs
CCT activity was assayed in the presence of 0–30 mm CTP and other standard conditions of the assay. The lipid vesicles were saturating concentrations (0.1–0.5 mm) of egg PC/PG (1:1). For the CCT-Δ22 and 236 variants, the dependence on [CTP] was sigmoidal, and these plots were evaluated in GraphPad Prism using the sigmoidal-variable slope to obtain values for S½. The analyses for WT-CCT utilized a Michaelis equation. Data are the average ± S.E. of at least two independent determinations.
| Lipid | CCT- WT |
CCT-Δ22 |
CCT-236 |
|||
|---|---|---|---|---|---|---|
| − | + | − | + | − | + | |
| Vmaxa | 240 ± 35 | 13,200 ± 990 | 3500 ± 200 | 13,000 ± 400 | 3350 ± 250 | 5550 ± 650 |
| S½·CTPb | 10 ± 3 | 0.9 ± 0.2 | 9.2 ± 1.4 | 2.3 ± 0.2 | 5.6 ± 0.9 | 7.6 ± 0.7 |
a Units are in nanomoles of CDP-choline/min/mg CCT.
b Units are in mm.