Table 2.
The detection limit of porcine kidney leucine aminopeptidase (PKLAP) with colorimetric and fluorescent substrates.
| Substrate | Background hydrolysis (nmol.min-1) |
Specific activity (μmol.min-1.mg-1) |
L.O.D.* (μg/mL) |
S/B# | S/N# | Z’# |
|---|---|---|---|---|---|---|
| I | 2.5 ± 0.1 | 5.1 ± 0.1 | 5.0 | 3.0 | 56 | 0.89 |
| II | 0.42 ± 0.02 | 9.6 ± 0.7 | 1.0 | 4.5 | 69 | 0.69 |
| III | 0.029 ± 0.007 | 0.044 ± 0.003 | 10.0 | 3.0 | 83 | 0.80 |
| IV | 0.34 ± 0.01 | 8.4 ± 0.5 | 1.0 | 4.8 | 93 | 0.79 |
| V | 0.019 ± 0.001 | 6.5 ± 0.4 | 0.05 | 3.4 | 83 | 0.76 |
*
Limit of Detection: minimum amount of PKLAP yielding a significantly measurable activity.
#
Values calculated for [E] = L.O.D. The signal to background ratio (S/B) was calculated by dividing the reaction average velocity in presence of enzyme (Av.enz.) by the average background hydrolysis rate (Av.blank). The signal to noise ratio (S/N) was calculated by dividing the reaction velocity in presence of enzyme by the standard deviation of the background hydrolysis (SDblank). The Z’ factor was calculated following the method of Zhang et al. [16] using the formula: Z’ = (1 − {[3*(SDenz. + SDblank)]/(Av.enz. − Av.blank)}.