Activity of glutathione reductase (GR; EC 1.6.4.2) was assayed as
a decrease in absorbance of NADPH at 340 nm according to
Schaedle and Bassham (1977) in 50 mM Tris–HCL (pH-7.6),
0.15 mM NADPH, 1 mM GSSG, 3 mM MgCl2 and enzyme extract.
Catalase activity (CAT; EC 1.11.1.6) was assayed according to the
method of Aebi (1984). Leaf sample of 0.1 g was homogenized at
4 C in 100 mM cold phosphate buffer containing 0.5% Triton-X.
Activity of CAT was assessed in 100 ml phosphate buffer, 400 ml
200 mM H2O2 and 100 ml enzymes. A decrease in H2O2 was
measured at 240 nm. Peroxidase activity (POX; EC 1.11.1.7) was
estimated in 0.1 g fresh leaf homogenized in 10 ml of 0.1 M
phosphate buffer and 5 mM cysteine. 5 ml assay mixture containing
2 ml 125 mM phosphate buffer, 1 ml 50 mM pyragallol, 1 ml
50 mM H2O2 and 1 ml of enzyme extract was incubated at 25 C for
5 min. The reaction was terminated after 5 min by adding 0.5 ml 5%
(v/v) concentrated H2SO4. Purpurogalin formed in the reaction was
extracted with 10 ml ether and absorbance was estimated at
420 nm (Britton and Mehley, 1955).
Activity of glutathione reductase (GR; EC 1.6.4.2) was assayed asa decrease in absorbance of NADPH at 340 nm according toSchaedle and Bassham (1977) in 50 mM Tris–HCL (pH-7.6),0.15 mM NADPH, 1 mM GSSG, 3 mM MgCl2 and enzyme extract.Catalase activity (CAT; EC 1.11.1.6) was assayed according to themethod of Aebi (1984). Leaf sample of 0.1 g was homogenized at4 C in 100 mM cold phosphate buffer containing 0.5% Triton-X.Activity of CAT was assessed in 100 ml phosphate buffer, 400 ml200 mM H2O2 and 100 ml enzymes. A decrease in H2O2 wasmeasured at 240 nm. Peroxidase activity (POX; EC 1.11.1.7) wasestimated in 0.1 g fresh leaf homogenized in 10 ml of 0.1 Mphosphate buffer and 5 mM cysteine. 5 ml assay mixture containing2 ml 125 mM phosphate buffer, 1 ml 50 mM pyragallol, 1 ml50 mM H2O2 and 1 ml of enzyme extract was incubated at 25 C for5 min. The reaction was terminated after 5 min by adding 0.5 ml 5%(v/v) concentrated H2SO4. Purpurogalin formed in the reaction wasextracted with 10 ml ether and absorbance was estimated at420 nm (Britton and Mehley, 1955).
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