TABLE 2.
Effects of several compounds, thiols, and metal ions on CPOMT activitya
| Compound, thiol, or metal ion addedb | Final concn (mM) | Relative activity (%)c |
|---|---|---|
| None | 100 | |
| MTHFd | 1 | 119 ± 11 |
| Glycerol | 1,085.7e | 122 ± 9 |
| l-Cys | 1 | 88 ± 10 |
| PMSF | 1 | 85 ± 6 |
| PMSF + DTT | 1 + 1 | 147 ± 12 |
| Ca2+ | 1 | 84 ± 4 |
| Cu2+ | 1 | 4 ± 1 |
| Fe2+ | 1 | 82 ± 9 |
| Hg2+ | 0.1 | 4 ± 1 |
| Zn2+ | 0.1 | 18 ± 5 |
| Ag+ | 1 | 6 ± 2 |
| Cs+ | 1 | 85 ± 3 |
| NH4+ | 1 | 84 ± 5 |
a
Other compounds (1 mM) and ions (1 mM) tested, such as EDTA, β-mercaptoethanol, DTT, thioglycolic acid, Mg2+, and Li+, did not have a significant effect on the activity (the variations observed were always less than 10% compared with the control reaction).
b
The enzymatic preparation in 50 mM Tris-HCl (pH 8.2) was preincubated with each compound or ion for 10 min before addition of the substrate.
c
The activity of the enzyme with no addition was assigned a value of 100. The values are means ± standard deviations.
d
MTHF, 5-methyltetrahydrofolic acid.
e
10% (vol/vol).