研究ノート
オーキシン生合成の2段階酵素反応の調節機構
2023 年 58 巻 1 号 p. 52-57
詳細
2023 年 58 巻 1 号 p. 52-57
Plant hormone, indole-3-acetic acid (IAA) is synthesized in a two-step enzymatic reactions involving tryptophan (Trp) aminotransferases (TAA1/TARs) and flavin monooxygenases (YUCs). In this study, we synthesized analogs of the reaction intermediate indole-3-pyruvic acid (IPyA), such as KOK2099, and demonstrated that IPyA regulates auxin biosynthesis at the level of enzyme regulation. Results from treatment of Arabidopsis seedlings indicated that the IPyA analogs are IAA biosynthesis inhibitor. Enzymatic studies with recombinant TAA1 showed that KOK2099 and IPyA inhibited TAA1 activity. When reacted sequentially of TAA1 and AtYUC10 to consume IPyA, the activity of TAA1 was significantly increased. Since aminotransferases are generally reversible, we tested the reverse reaction activity of TAA1. TAA1 has the activity to convert IPyA to Trp. IPyA levels are maintained by the push (by TAA1/TARs) and pull (by YUCs) of the two biosynthetic enzymes, in which TAA1 plays a key role in preventing the over- or under-accumulation of IPyA.
