Induction of N-Hydroxycinnamoyltyramine Synthesis and Tyramine N-Hydroxycinnamoyltransferase (THT) Activity by Wounding in Maize Leaves

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Both N-p-coumaroyl-and N-feruloyltyramine accumulated in response to wounding in leaf segments of maize. The amount of N-hydroxycinnamoyltyramines started to increase 3-6 h after wounding and peaked at 12h. Thereafter, the amount of N-p-coumaroyltyramine decreased rapidly, while the N-feruloyltyramine content remained at a high level. The accumulation of N-hydroxycinnamoyltyramines was accompanied by an increase in the tyramine N-hydroxycinnamoyltransferase (THT) activity. This increase was initially detected 3h after wounding and reached a maximum at 36h, the level of activity being 40 and 11 times that in the leaves before wounding and in the control leaves, respectively. Partial purification of THT from wounded leaves by (NH_4)_2SO_4 precipitation and subsequent two steps of anion-exchange chromatography resulted in a 12.5-fold increase in specific activity. Kinetic studies with this partially purified enzyme revealed that the best substrates were tyramine and feruloyl-CoA, although tryptamine and sinapoyl-CoA also efficiently served as substrates. The apparent native molecular weight of the enzyme was determined by gel filtration as 40 kDa.
社団法人日本農芸化学会の論文
2000-05-23