벼 유식물을 이용한 C29-Brassinosteroids의 대사

Abstract

It has been recently demonstrated the presence of not only C28-BRs biosysnthesis, but also C27- and C29-BRs biosynthesis in plants, suggesting that BRs biosynthesis are complicatedly connected to produce biologically active BR (s). This prompted us to investigation of metabolism of a C29-BR, 28-homoCS in seedlings of rice from which C29-BRs such as 28-homoTE and 28-homoTY have been identified. In vitro enzyme conversion study using a crude enzyme solution prepared from rice seedlings revealed that 28-homoCS is converted into both CS and 26-nor-28-homoCS, but their reversed reaction did not occur. This indicated that 28-homoCS is biosynthetically converted into more biologically active C28-BR, CS by C-28 demethylation and biodegraded into 26-nor-28-homoCS by C-26 demethylation. Next, bio-conversion of 28-homoCS to 28-homoBL was examined by the same enzyme solution. No 28-homoBL as a metabolite of 28-homoCS was detected, meaning that biosynthetic reaction for 28-homoCS to 28-homoBL is not contained, and main connection of C28-BRs and C29-BRs biosynthesis is between CS and 28-homoCS in the rice seedling. This study is the first demonstrated that C29-BRs and C28-BRs bionsynthetic pathways are connected, and that C29-BRs biosynthetic pathway is an alternative biosynthetic pathway to produce more biologically active C28-BR, CS in plant.