Table 2.
Summary of constants Vmax and Kact of PMCA activity in raft and non-raft fractions of SPMs isolated from 6 mos old rat brain and measured in the presence or absence of exogenous CaM.
| Pooled Fractionsa | Vmax (nmol Pi mg−1 protein min−1)b | Kact (μM) | ||
|---|---|---|---|---|
| No CaM | Plus CaMc | No CaM | Plus CaMc | |
| 2 – 4 | 16.7 ± 0.8 | 16.8 ± 0.7 | 0.023 ± 0.004 | 0.011 ± 0.006 |
| 5 – 6 | 7.4 ± 1.2 | 7.7 ± 1.4 | 0.088 ± 0.059 | 0.065 ± 0.037 |
| 7 – 9 | 4.1 ± 0.5 | 3.9 ± 0.1 | 0.049 ± 0.042 | 0.046 ± 0.040 |
a
PMCA activity was measured in pooled fractions isolated by Brij98 treatment of SPMS followed by sucrose density centrifugation.
b
Values represent the mean ± SEM of constants obtained from the analyses of Michaelis-Menten fitting of the data from 5 rats per group (all measurements performed in triplicate).
c
The concentration of CaM added was 300 nM.