2001 年 36 巻 p. 39-40
Several cytochromes P450 are involved in gibberellin (GA) biosynthesis. We have isolated. two cDNAs from tomato, to88B1 and to707A5, specifically expressed in ovary. The cDNAs showed high homology to CYP88A (ent-kaurenoic acid oxidase in GA biosynthesis) in phylogenetic analysis, suggesting that both P450s may be in GA biosynthesiS. Because of only 40% identity to CYP88A, to88B1 may have a different function from CYP88A. Furthermore, the Thr residue conserved in most P450s, which plays an important role to stabilize the ferrous P450-O_2 intermediate, is substituted for Pro in to88B 1. GA biosynthetic pathway has a side branch that lead ent-kaurenoic acid to kaurenolides by C6-desaturation, and to88B1 may be involved in the pathway, together with to707A5. To confirm this, the P450s were expressed in insect cells and the measurement of their activities is in progress.