For enzyme activity assay, 10 g of sarcocarp samples around the
infection spots from 15 fruits were ground in mortar using liquid
nitrogen. All the enzymes were extracted at 4 C and the absorbance
was determined by UV-160 spectrophotometer (Shimadzu,
Japan). The activity of phenylalanine ammonia-lyase (PAL) was
detected following the methods of Yao and Tian (2005). PAL was
extracted with 25 mL of 0.05 mol/L sodium borate buffer (pH 8.8,
containing 5 mmol/L b-mercaptoethanol).1 mL enzyme extractwas
incubated with 2 mL of borate buffer (50 mmol/L, pH 8.8) and 1 mL
of L-phenylalanine (20 mmol/L) for 60 min at 37 C. The reaction
was stopped with 1 mL HCl (1 mol/L). PAL activity was determined
by the production of cinnamate, which was measured by absorbance
at 290 nm. The activity of polyphenoloxidase (PPO) was
assayed following the methods of Tian, Xu, Jiang, and Qin (2002).
PPO was extracted with 25 mL 0.2 mol/L sodium phosphate buffer
(pH 6.4). For enzyme detection, 3 mL 0.5 mol/L 4-methylcatechol in
0.2 mol/L sodium phosphate buffer (pH 6.4) and 100 mL enzyme
For enzyme activity assay, 10 g of sarcocarp samples around theinfection spots from 15 fruits were ground in mortar using liquidnitrogen. All the enzymes were extracted at 4 C and the absorbancewas determined by UV-160 spectrophotometer (Shimadzu,Japan). The activity of phenylalanine ammonia-lyase (PAL) wasdetected following the methods of Yao and Tian (2005). PAL wasextracted with 25 mL of 0.05 mol/L sodium borate buffer (pH 8.8,containing 5 mmol/L b-mercaptoethanol).1 mL enzyme extractwasincubated with 2 mL of borate buffer (50 mmol/L, pH 8.8) and 1 mLof L-phenylalanine (20 mmol/L) for 60 min at 37 C. The reactionwas stopped with 1 mL HCl (1 mol/L). PAL activity was determinedby the production of cinnamate, which was measured by absorbanceat 290 nm. The activity of polyphenoloxidase (PPO) wasassayed following the methods of Tian, Xu, Jiang, and Qin (2002).PPO was extracted with 25 mL 0.2 mol/L sodium phosphate buffer(pH 6.4). For enzyme detection, 3 mL 0.5 mol/L 4-methylcatechol in0.2 mol/L sodium phosphate buffer (pH 6.4) and 100 mL enzyme
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