Effect of divalent cations on PON1 lactonase activity
| Substrate | Ca2+ | Zn2+ | Mg2+ |
|---|---|---|---|
| μmol/min/ml enzyme preparation (%)7-a | μmol/min/ml enzyme preparation (%) | μmol/min/ml enzyme preparation (%) | |
| Phenyl acetate | 66.3 ± 1.2 (100) | 0.21 ± 0.03 (0.3) | 2.93 ± 0.06 (4.4) |
| Homogentisic acid lactone | 34.7 ± 0.9 (100) | 0.40 ± 0.08 (1.2) | 1.74 ± 0.02 (5.0) |
| δ-Valerolactone | 41.0 ± 1.7 (100) | 0.24 ± 0.05 (0.6) | 2.66 ± 0.19 (6.5) |
| Undecanoic-δ-lactone | 14.2 ± 0.1 (100) | 0.21 ± 0.02 (1.5) | 0.96 ± 0.05 (6.8) |
| ɛ-Caprolactone | 9.58 ± 0.1 (100) | 0.26 ± 0.05 (2.7) | 0.86 ± 0.04 (9.0) |
Calcium ions were removed from the purified PON1 sample using a chelating agent and replaced by zinc and magnesium ions. Calcium ions were also replaced to demonstrate recovery of activity; the activities of other samples are compared with those of this preparation. Substrate concentrations used were 1 mM. Each value represents the mean value of triplicate assays ± S.D.
↵7-a Percent (%) is defined as the percent activity compared to values obtained in the presence of calcium chloride (1 mM).