Table II.
Substrate specificity of potato anionic peroxidase
| Substrate (refer to Scheme 1) | Vmaxapp | Relative Activitya |
|---|---|---|
| pkat | ||
| 1ap-Coumaric acid | 9.5 | 3.1 |
| 1bN-(p-Coumaroyl)tyramine | 70.6 | 22.9 |
| 1cN-(p-Coumaroyl)putrescine | 51.1 | 16.6 |
| 1dp-Coumaroylglucose | 50.0 | 16.2 |
| 1ep-Coumarate-4-O-β-d-glucoside | <1b | 0.3 |
| 2a Caffeic acid | 163.4 | 53.1 |
| 2bN-Caffeoyltyramine | 129.6 | 42.1 |
| 2h Chlorogenic acid | 137.7 | 44.7 |
| 3a Ferulic acid | 307.8 | 100 |
| 3bN-Feruloyltyramine | 318.6 | 103.5 |
| 3cN-Feruloylputrescine | 366.0 | 118.9 |
| 3d Feruloylglucose | 379.9 | 123.5 |
| 3e Ferulate-4-O-β-d-glucoside | <1b | 0.3 |
| 3fN-Feruloyloctopamine | 258.1 | 83.8 |
| 3gN-Feruloyl-(2-phenyl)-ethylamine | 376.0 | 122.2 |
| 4a Sinapic acid | 34.6 | 11.2 |
| 4bN-Sinapoyltyramine | 32.2 | 10.5 |
| 4d Sinapoylglucose | 15.9 | 5.2 |
| 4e Sinapate-4-O-β-d-glucoside | <1b | 0.3 |
| 5ap-Coumaryl alcohol | 3.6b | 1.2 |
| 5bp-Coumaryl alcohol-4-O-β-d-glucoside | 2.2b | 0.7 |
| 6a Coniferyl alcohol | 174.6 | 56.7 |
| 6b Coniferin | <1b | 0.3 |
| 7a Sinapyl alcohol | 12.5b | 4.1 |
| 7b Syringin | 2.2b | 0.7 |
Maximum catalytic rates were determined for each substrate by measuring the initial rate of their consumption over a range of concentrations (0–0.2 mm) with a fixed concentration of H2O2 (2 mm). The rate values were predicted from the intercepts of Wolfe-Hanes plots. For all assays, the purified potato anionic peroxidase was used at a 0.5 nm final concentration.
a
Ferulic acid set to 100%.
b
Maximum rate measured; substrate did not show typical saturation kinetics, precluding the use of the Wolfe-Hanes transformation.