Table 3.
Summary of constants Vmax and Kact of PMCA activity in raft domains isolated from SPMs from 6, 23, and 34 mos old rats and measured in the presence or absence of exogenous CaM.
| Age (Months) | Vmaxa (nmol Pi mg−1 protein min−1)b | Kacta (μM) | ||
|---|---|---|---|---|
| No CaM | Plus CaMc | No CaM | Plus CaMc | |
| 6 | 17.5 ± 0.6 | 16.5 ± 0.8 | 0.033 ± 0.005 | 0.015 ± 0.007 |
| 23 | 13.4 ± 1.1 | 13.5 ± 0.5 | 0.026 ± 0.008 | 0.0078 ± 0.01 |
| 34 | 10.7 ± 1.8 | 10.8 ± 1.1 | 0.037 ± 0.01 | 0.011 ± 0.004 |
a
PMCA activity measured as described in Table 2.
b
Values represent the mean ± SEM of constants obtained from the analyses of Michaelis-Menten fitting of the data from 4 rats per group (all measurements performed in triplicate).
c
The concentration of CaM added was 300 nM.