43 原核生物に見出されたジテルペンサイクラーゼの機能解析(口頭発表の部)

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Eubacterial diterpene cyclase genes had previously been cloned from a diterpenoid-antibiotic, terpentecin producer. Their products, Cyc1 and Cyc2, were essential for the conversion of geranylgeranyl diphosphate (GGDP) into terpentetriene (TTE) that had the same basic skeleton as terpentecin. In this study, functional analyses of these two enzymes were performed by using purified recombinant enzymes. The Cyc1 product converted GGDP into a cyclized intermediate (terpentedienol diphosphate, TDP), which was then transformed into TTE by the Cyc2 product. Interestingly, the Cyc2 product directly catalyzed conversion of GGDP into three olefinic compounds. Moreover, the Cyc2 product utilized farnesyl diphosphate (FDP) as a substrate to give three olefinic compounds, which had the same structures as those formed from GGDP except for the chain-lengths. These results suggested that the Cyc1 product with a DXDD motif converted GGDP into TDP by a protonation-initiated cyclization and that the Cyc2 product with a DDXXD motif completed the transformation of TDP to the olefin, terpentetriene by an ionization-initiated reaction followed by deprotonation. Kinetics of the Cyc2 product indicated that the affinity for TDP and GGDP were higher than that of FDP and that the relative activity of the reaction converting TDP into TTE was highest among the reactions using TDP, GGDP, or FDP as the substrate. These results suggested that an actual reaction catalyzed by the Cyc2 was the conversion of TDP into TTE in vivo.
天然有機化合物討論会の論文
2002-09-01

43 原核生物に見出されたジテルペンサイクラーゼの機能解析(口頭発表の部)

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