Chlorophyllase activity was determined according to the method described by Hornero-Méndez and Mínguez-Mosquera (2002) and Amir-Shapira et al. (1987) with minor modification. The reaction mixture containing 0.1 μM Chl a acetone solution, 100 mM Tris–HCl buffer (pH 8.5) and enzyme solution in a ratio of 1:5:5 was prepared. The mixture was incubated in a water bath at 50 °C for 1 h, and the reaction was terminated by the addition of 4 mL cold acetone. The remaining (non-degraded) Chls were extracted with 4 mL of hexane. The mixture was vigorously stirred until emulsion formation, and then centrifuged at 10,000 × g for 5 min at 4 °C. Chlorophyllase activity was assayed by measuring the absorbance at 667 nm of the lower acetone phase. The amounts of chlorophyllide (Chlide) generated were determined using extinction coefficients of 7.49 × 10−2 M−1 cm−1 and the enzyme activity was represented as mmol Chlide min−1 g−1 FW.
Mg-dechelatase activity was assayed by a modified procedure according to Vicentini et al. (1995). The reaction mixture comprised 2790 μL of 50 mM Tris–HCl buffer (pH 9.0, containing 0.1% (v/v) Triton X-100), 10 μL of Chlin a, and 200 μL of crude enzyme extract in a total volume of 3 mL. The mixture was incubated at 25 °C for 30 min. The increase of 0.001 in absorbance at 687 nm in 30 min was defined as one unit (U) of enzyme activity. Activity was expressed as U min−1 g−1 FW.